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DEC-XV-LMLAA-A-D

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Document:	MAC11 XVM Assembler Language Manual
Order Number:	DEC-XV-LMLAA-A-D
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Pages:	114
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OCR Text

MAC11 XVM ASSEMBLER
LANGUAGE MANUAL
DEC-XV-LMLAA-A-D

digital equipment corporation · maynard. massachusetts

First Printing, December 1975
The information in this document is subject to change without notice
and should not be construed as a commitment by Digital Equipment
Corporation. Digital Equipment Corporation assumes no responsibility
for any errors that may appear in this document.
The software described in this document is furnished under a license
and may be used or copied only in accordance with the terms of such
license.
Digital Equipment Corporation assumes no responsibility for the use or
reliability of its software on equipment that is not supplied by
DIGITAL.

(S) 1975 by Digital Equipment Corporation

The postage prepaid READER'S COMMENTS form on the last page of this
document requests the user's critical evaluation to assist us in preparing future documentation.

The following are trademarks of Digital Equipment Corporation:

DIGITAL
DEC
PDP
DECUS
UNIBUS
COMPUTER LABS
COMTEX
DDT
DECCOMM

DECsystem-lO
DECtape
DIBOL
EDUSYSTEM
FLIP CHIP
FOCAL
INDAC
LAB-8

MASSBUS
OMNIBUS
OS/8
PHA
RSTS
RSX
TYPESET-8
TYPESET-10
TYPESET-ll

1/76-15

CONTENTS
Page
PREFACE

CHAPTER 1
1.1
1.1.1
1.1. 2
1.1. 3
1.2
1.3
1.4
1.5
1. 5.1
1. 5.2
1.6

CHAPTER 2
2.1
2.1.1
2.1. 2
2.1. 3
2.1. 4
2.2
CHAPTER 3
3.1
3.1.1
3.1. 2
3.1. 3
3.2
3.2.1
3.2.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9

CHAPTER 4
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
4.10
4.ll

FUNDAMENTALS OF PROGRAMMING THE PDP-II

1-1

MODULAR PROGRAMMING
Commenting PDP-II Assembly Language Programs
Localized Register Usage
Conditional Assemblies
REENTRANT CODE
PREFERRED ADDRESSING MODES
PARAMETER ASSIGNMENTS
SPACE VS.
TIMING TRADEOFFS
Trap Handler
Register Increment
CCNDITIONAL BRANCH INSTRUCTIONS

1-1
1-2
1-2
1-4
1-4
1-4
1-5
1-5
1-5
1-6
1-6

SOURCE PRCGRAM FORMAT

2-1

STATEMENT FORMAT
Label Field
Operator Field
Operand Field
Comment Field
FORMAT CONTROL

2-1
2-1
2-3
2-3
2-3
2-4

SYMBOLS AND EXPRESSIONS

3-1

CHARACTER SET
Separating and Delimiting Characters
Illegal Characters
Operator Characters
MACll SYMBOLS
Permanent Symbols
User-Defined and MACRO Symbols
DIRECT ASSIGNMENTS
REGISTER SYMBOLS
LOCAL SYMBOLS
ASSEMBLY LOCATION COUNTER
NUMBERS
TERMS
EXPRESSIONS

3-1
3-2
3-4
3-4
3-5
3-5
3-5
3-6
3-7
3-8
3-10
3-11
3-11
3-12

ADDRESSING MODES

4-1

REGISTER MODE
REGISTER DEFERRED MODE
AUTO INCREMENT MODE
AUTOINCREMENT DEFERRED MODE
AUTODECREMENT MODE
AUTODECREMENT DEFERRED MODE
INDEX MODE
INDEX DEFERRED MODE
IMMEDIATE MODE
ABSOLUTE MODE
RELATIVE MODE

4-2
4-2
4-2
4-3
4-3
4-3
4-3
4-4
4-4
4-4
4-5

iii

CONTENTS (Cant.)
Page
4.12
4.13
4.14

CHAPTER 5
5.1
5.1.1
5.1. 2
5.1. 3
5.1. 4
5.1. 5
5.2
5.3
5.3.1
5.3.2
5.3.3
5.3.4
5.3.5
5.3.6
5.4
5.4.1
5.4.2
5.5
5.5.1
5.5.2
5.5.3
5.6
5.6.1
5.7
5.7.1
5.7.2
5.7.3

CHAPTER 6
6.1
6.1.1
6.1. 2
6.1. 3
6.1. 4
6.2
6.3
6.3.1
6.3.2
6.3.3
6.3.4
6.3.5
6.3.6
6.4
6.5
6.6
6.7
CHAPTER 7
7.1
7.2
7.3

RELATIVE DEFERRED MODE
TABLE OF MODE FORMS AND CODES
BRANCH INSTRUCTION ADDRESSING

4-5
4-5
4-6

GENERAL ASSEMBLER DIRECTIVES

5-1

LISTING CONTROL DIRECTIVES
.LIST and .NLIST
Page Headings
.TITLE
.SBTTL
Page Ejection
FUNCTIONS:
. ENABL AND . DSABL DIRECTIVES
DATA STORAGE DIRECTIVES
.BYTE
.WORD
ASCII Conversion of One or Two Characters
.ASCII
.ASCIZ
.RAD50
RADIX CONTROL
.RADIX
Temporary Radix Control:
AD, AO, and AB
LOCATION COUNTER CONTROL
.EVEN
.ODD
.BLKB and .BLKW
TERMINATING DIRECTIVES
.END
CONDITIONAL ASSEMBLY DIRECTIVES
Subconditionals
Immediate Conditionals
PAL-IIR Conditional Assembly Directives

5-1
5-1
5-3
5-3
5-5
5-7
5-7
5-8
5-8
5-9
5-10
5-11
5-12
5-12
5-14
5-14
5-14
5-15
5-15

MACRO DIRECTIVES

6-1

MACRO DEFINITION
.NACRO
. .ENDM
.MEXIT
MACRO Definition Formatting
MACRO CALLS
ARGUMENTS TO MACRO CALLS AND DEFINITIONS
Macro Nesting
Special Characters
Numeric Arguments Passed as Symbols
Number of Arguments
Automatically Created Symbols
Concatenation
.NARG, .NCHR, AND .NTYPE
.ERROR AND .PRINT
.IRP AND . IRPC
INDEFINITE REPEAT BLOCK:
.REPT
REPEAT BLOCK:

6-1
6-1
6-2
6-2
6-3
6-3
6-4
6-4
6-5
6-6
6-7
6-7
6-8
6-9
6-10
6-11
6-13

OPERATING PROCEDURES

7-1

LOADING MAC 11
COMMAND INPUT STRING
PAPER TAPE SOURCES

7-1
7-1
7-2

5-16

5-16
5-17
5-17
5-18
5-20
5-21
5-22

CONTENTS (Cont.)
APPENDICES
Page
APPENDIX A
A.l
A.2

MACII CHARACTER SETS
ASCII CHARACTER SET
RADIX-50 CHARACTER SET

A-I
A-I
A-4

APPENDIX B
B.l
B.2
B.3
B.3.1
B.3.2
B.3.3
B.3.4
B.3.5
B.3.6
B.3.7
B.4

MACII ASSEMBLY LANGUAGE AND ASSEMBLER
SPECIAL CHARACTERS
ADDRESS MODE SYNTAX
INSTRUCTIONS
Double-Operand Instructions
Single-Operand Instructions
Operate Instructions
Trap Instructions
Branch Instructions
Register Destination
Subroutine Return
ASSEMBLER DIRECTIVES

B-1
B-1
B-2
B-3
B-4
B-4
B-6
B-7
B-8
B-9
B-9
B-lO

APPENDIX C

PERMANENT SYMBOL TABLE

C-l

APPENDIX D
D.l

ERROR MESSAGE SUMMARY
MACll ERROR CODES

D-l
D-l

INDEX

INDEX-l
FIGURES

FIGURE

1-1
1-2
3-1
5-1
5-2
6-1

Problem-Oriented Tree-Structure
1-3
Segment of PDP-II Code Showing 1, 2, and
3-Word Instructions
1-3
Assembly Source Listing of MACII Code Showing
3-9
Local Symbol Blocks
5-4
Example of ~~Cll Line Printer Listing
5-6
Assembly Listing Table of Contents
6-12
.IHP and . IRPC Example
TABLES

TABLE

3-1
3-2

Legal Separating Characters
Legal Delimiting Characters

3-3
3-3

LIST OF ALL XVM MANUALS

The following is a list of all XVM manuals and their DEC numbers, including the latest version available.

Within this manual, other XVM

manuals are referenced by title only.

Refer to this list for the

DEC numbers of these referenced manuals.
BOSS XVM USER'S MANUAL

DEC-XV-OBUAA-A-D

CHAIN XVM/EXECUTE XVM UTILITY MANUAL

DEC-XV-UCHNA-A-D

DDT XVM UTILITY MANUAL

DEC-XV-UDDTA-A-D

EDIT/EDITVP/EDITVT XVM UTILITY MANUAL

DEC-XV-UETUA-A-D

8TRAN XVM UTILITY MANUAL

DEC-XV-UTRNA-A-D

FOCAL XVM LANGUAGE MANUAL

DEC-XV-LFLGA-A-D

FORTRAN IV XVM LANGUAGE MANUAL

DEC-XV-LF4MA-A-D

FORTRAN IV XVM OPERATING ENVIRONMENT MANUAL

DEC-XV-LF4EA-A-D

LINKING LOADER XVM UTILITY MANUAL

DEC-XV-ULLUA-A-D

MACll XVM ASSEMBLER LANGUAGE MANUAL

DEC-XV-LMLAA-A-D

MACRO XVM ASSEMBLER LANGUAGE MANUAL

DEC-XV-LMALA-A-D

MTDUMP XVM UTILITY MANUAL

DEC-XV-UMTUA-A-D

PATCH XVM UTILITY MANUAL

DEC-XV-UPUMA-A-D

PIP XVM UTILITY MANUAL

DEC-XV-UPPUA-A-D

SGEN XVM UTILITY MANUAL

DEC-XV-USUTA-A-D

SRCCOM XVM UTILITY MANUAL
UPDATE XVM UTILITY MANUAL
VP1SA XVM GRAPHICS SOFTWARE MANUAL

DEC-XV-USRCA-A-D
DEC-XV-UUPDA-A-D
DEC-XV-GVPAA-A-D

VT1S XVM GRAPHICS SOFTWARE MANUAL

DEC-XV-GVTAA-A-D

XVM/DOS KEYBOARD COMMAND GUIDE
XVM/DOS READER'S GUIDE AND MASTER INDEX

DEC-XV-ODKBA-A-D
DEC-XV-ODGIA-A-D

XVM/DOS SYSTEM MANUAL

DEC-XV-ODSAA-A-D

XVM/DOS USERS MANUAL
XVM/DOS ViA SYSTEM INSTALLATION GUIDE

DEC-XV-ODMAA-A-D

XVM/RSX SYSTEM ~ffiNUAL

DEC-XV-IRSMA-A-D

XVM UNICHANNEL SOFTWARE MANUAL

DEC-XV-XUSMA-A-D

vii

DEC-XV-ODSIA-A-D

PREFACE

This manual describes the PDP-II MACRO-II Assembler
(MACII)
and
Assembly Language and discusses briefly how to program the PDP-II
computer.
It is recommended that the reader have copies of the PDP-II
Processor
Handbook and, optionally,
the PDP-II Peripherals and
Interfacing Handbook.
References are made to
these
documents
throughout this manual
(although this document is complete, the
additional material provides further details).
The user
is also
advised
to obtain a
PDP-II pocket Instruction List card for easy
reference.
(These items can be obtained from the Digital Software
Distribution Center.)
This MACRO-II Assembler operates under
the XVM/DOS
(Disk Operating
System)
in conjunction with PIREX, a multiprogramming executive
running on a PDP-II in the XVM UNICHANNEL configuration system.
Some notable features of MACII are:
1.

Device and filename specifications for input

Error listing on command output device

Alphabetized, formatted symbol table listing

Conditional assembly directives

User defined macros

Extensive listing control

Associated Documents:
PDP-II/05/10/35/40 Processor Handbook
PDP-II Peripherals and Interfacing Handbook
XVM UNICHANNEL Software Manual
XVM/DOS Users Manual
EDIT/EDITVP /EDITVT XVM Utili ty ~lanual
PIP XVM Utility Manual
The MACII assembler, a subset of the standard MACRO-II assembler
for
the PDP-II,
is specifically written for the VXM system.
Programs
written for the MACRO-II assembler will not necessarily assemble
correctly with MACII,
and programs written for
MACII will
not
necessarily assemble correctly with MACRO-II.
The MACII assembler generates only absolute binary output.

CHAPTER 1
FUNDAMENTALS OF PROGRAMMING THE PDP-II

This Chapter presents some fundamental software concepts essential
to
efficient assembly language programming- of the PDP-II computer.
A
description of the hardware components of the PDP-II
family can be
found in the two DEC paperback handbooks:
PDP-II Processor Handbook
PDP-li Peripherals and Interfacing Handbook
No attempt is made in this document to'describe the PDP-II hardware or
the
function of the various PDP-II
instructions.
However, it is
recommended that the reader become familiar with this material before
proceeding.
The new PDP-II programmer is advised
to
read
this Chapter before
reading
further
in this manual.
The concepts in this Chapter will
create a conceptual matrix within which explanations of the
language
fit.
Since the techniques described herein work best with the PDP-II
and are used in PDP-II system programs, they should be considered from
the very start of your PDP-II programming experience.

1.1

MODULAR PROGRAMMING

The PDP-II family of computers lend
themselves most easily to a
modular
system of programming.
In such a system the programmer must
envision the entire program and break
it down into constituent
subroutines.
Modular development forces an awareness of the final
system.
Ideally, this should cause all components of the system to be
considered
from
the very beginning of the development effort rather
than patched into a partially-developed system.
This provides for the
best use of the PDP-II hardware (as discussed later in this Chapter) ,
and results in programs which are more easily modified
than
those
coded with straight-line coding techniques.
To this end, flowcharting of the entire system is
to coding rather
than during or
after
the
programmer is then able to work on small portions
time.
Subroutines of approximately one or two
desirable.

best performed prior
coding effort.
The
of the program at a
pages are considered

Modular programming practices maximize
the
usefulness
of
an
installation's resources.
Programmed modules can be used in other
programs or systems having similar or identical functions without the
expense of redundant development .
Also software modules developed as

1-1

FUNDAMENTALS OF PROGRAMMING THE PDP-II
functional entities are more likely to
be free of serious logical
errors as a
result of the original programming effort.
The use of
such modules will
simplify the development of later
systems by
incorporating proven pieces.
Modular development provides for ease of use and modification rather
than
simplifying
the original development.
While care must be taken
in the beginning to ensure correct modular
system development,
the
benefits
of
standardization
to
the generation of maintenance
programmers which deal with a given assembly are many.
(See also
the
notes under Commenting Assembly Language Programs.)
PDP-II assembly language programming
best follows
a
tree-like
structure with the
top of the tree being the final results and the
base being the smallest component function.
(The Assembler itself is
a tree structure and is briefly described in Figure 1-1.)

1.1.1

Commenting PDP-II Assembly Language Programs

When programming in a modular fashion,
it is desirable
to heavily
comment
the beginning of each subroutine, telling what that routine
does:
its inputs, outputs, and register usage.
Since subroutines are short and encompass only one operation it is not
necessary to tell how the subroutine functions, but only what it does.
An explanation of how a subroutine functions should be documented only
when
the procedure
is not obvious to the reader.
This enables any
later inspection of an unclear
subroutine
to disclose
the maximum
amount of useful information to the reader.

1.1.2

Localized Register Usage

A useful technique in writing subroutines is
to save all
registers
upon entering a
subroutine and
restore
them prior to leaving the
subroutine.
This allows the programmer unrestricted use of the PDP-II
registers, including the program stack, during a subroutine.
Use of registers avoids 2- and 3-word addressing
instructions.
The
code
in Figure 1-2 compares
the
use of registers with symbolic
addressing.
Register use is faster and requires less storage
space
thatn symbolic addressing.

1-2

FUNDAMENTALS OF PROGRAMMING THE PDP-II

Source
Program
Input

Line
'I'erminator

Operand

Macro
Processor

Figure 1-1
Problem-Oriented Tree-Structure
I.

00000:1.

O()OO()~;

,.:..

;EXAMPLE OF MANIPULATION WITH SYMBOLIC ADDRESSING.

-4
1::"

'6"' OOO()()O 06 2767 BEGIN:

ADD 1 3,VALUE

;3 WORD INSTRUCTION.

CMP VA LU E,KEEP

;3 WORDS.

BEG NEXT
MOV VALUE,KEEP

;3 WORDS.

O()0003
() 0 () 0 ~::; ;:,

"7 000006 0;:.'6767
OO()046
OO()046
B O()OO:l.4 0014()3
9 O()O()16 0 :1. 6"767
O()()036
000036
to 00024 OO~:;167 NEXT:
OOOO::l2
:1 1 000:30 .1.0()01 2
1 ;.' 000:32 OO~:)06?

COM I<EEP
BPI... DONE
CI...F( KE EP

O()0024
13
14

;NOW DO THE SAME THING WITH REGI STERS.

1 ~:j

16 00036 062?Ol
OO()()03
17 00042 020102
:ttl 00044 O()I.40J
:1.9 O()()46 010:1.02
20 OO()50 005:1.0 2 NEXT:I.:
21

()()O~:'j2

.I. OO()O:l.

2~'.

O()O~:'j4

OO~:'j002

24 00056 O()OO():I. DONE:

• f~ :I.
eMP F':I. , F,2

AD D :11:]

BEn NEXT1
110l) F:: 1 , F(::>'
COM F"' ...·)..
DPI... DONE
CI...F( F~2

; 2 lJ f:; 3

l'JD h: D~:;

0: L

INE 6 • (.lBDl)E )

; :I.

l) ~:; :5

~JnF::D~:>

( L

INE

"/ )

[; 1

l.} ~:; ,.,··X

~JDRD ~:;

( L IHE

':? )

•1

t) ~:)

::.::

IAIOF<D ~:;

( I.. INE

10 )

.
..

, :I. l,h; ,", l.JDF(D~:) ( L Ii'lE 1::) ) ,.

I..,JAIT

Figure 1-2
Segment of PDP-1l Code
Showing 1, 2, and 3-Word Instructions

1-3

FUNDAMENTALS OF PROGRAMMING THE PDP-II
1.1.3

Conditional Assemblies

Conditional assemblies are valuable in macro definitions.
The
expansion of a macro can be altered during assembly as a result of
specific arguments passed and their use in conditionals. For example,
a macro can be written to handle a given data item differently,
depending upon the value of the item. Only a single algorithm need be
expanded with each macro call.
(Conditionals are described in detail
in Section 5.7.)
Conditional assemblies can also be used to generate different versions
of a program from a single source. This is usually done as a result
of one or more symbols being either defined or undefined. Conditional
assemblies are preferred to the creation of a mUltiplicity of sources.
This principle is followed in the creation of PDP-II system programs
for the following reasons:

1.2

Maintenance of a single source program is easier, and
guarantees that a change in one version of the program, which
may affect other versions, is reflected automatically in all
possible versions.

Distribution of a single source program allows a customer or
individual user to tailor a system to his configuration and
needs and continue to update the system as the hardware
environment or programming requirements change.

As in the case of maintenance, the debugging and checkout
phase of a single program (even one containing many separate
modules) is easier than testing several distinct versions of
the same basic program.

REENTRANT CODE

Both the interrupt handling hardware and the
subroutine
call
instructions (JSR, RTS, EMT, and TRAP) facilitate writing reentrant
code for the PDP-II. Reentrant code allows a single copy of a given
subroutine or program to be shared by more than one process or task.
This reduces the amount of core needed for multi-task applications
such as the concurrent servicing of peripheral devices.
On the PDP-II, reentrant code depends upon the stack for storage of
temporary data values and the current processing status. Presence of
of
information in the stack is not affected by the changing
operational control from one task to another. Control is always able
to return to complete an operation which was begun earlier but not
completed.

1.3

PREFERRED ADDRESSING MODES

Addressing modes are described in detail in Chapter 4. Basically, the
PDP-II programmer has eight types of register addressing and four
types of addressing through the PC register.
Those operations
involving general register addressing take one word of core storage,
while symbolic addressing can use up to three words. For example:
MOV A,B
MOV RO,Rl

;THREE WORDS OF STORAGE
:ONE WORD OF STORAGE

1-4

FUNDAMENTALS OF PROGRAMMING THE PDP-II
The user is advised to perform as many operations as possible with
register addressing modes, and to use the remaining addressing mod e s
to preset the registers for an operation.
This technique saves space
and time over the course of a program.

1.4

PARAMETER ASSIGNMENTS

Parameter assignments should be used to e nable a program to be easily
followed through the use of a s ymbolic cross reference (CREF listing).
For example:
SYM=42

MOV #SYM,RO
Another standard PDP-II convention is to name the general registers as
follows:
RO
Rl
R2
R3
R4
RS
SP
PC

1.S

SPACE VS.

%0
%1
%2

%3
%4

%S
(processor stack pointer)
(program counter)

TIMING TRADEOFFS

On the PDP-ll as on all computers, some techniques lead to savings in
storage space and others lead to decreased execution time.
Only the
individual user can determine which is the best combination of the two
for
his application.
It is the purpose of this section to describe
several means of conserving core storage and / or saving time.

1.S.1

Trap Handler

The use of the trap handler
and a dispatch table conserves core
requirements in subroutine calling,
but can lead to a decrease in
execution speed due to indirect transfer of control.
To illustrate, a
subroutine call can be made in either of the following ways:
1.

A JSR instruction which generally requires two PDP-ll words:
JSR

RS,SUBA

but is direct and fast.
2.

A TRAP instruction which requires one in-line PDP-ll word:
TRAP N
but is indirect and slower.
The TRAP handler must use N to
index through a dispatch table of subroutine addresses and
then JMP to the Nth subroutine in the table.

l-S

FUNDAMENTALS OF PROGRAMMING THE PDP-II
1.5.2

The operation:
CMPB

(RO)+,(RO)+

is preferable to:
TST

(RO)+

to increment RO by 2, especially where the initial contents of RO
be odd.

1.6

may

CONDITIONAL BRANCH INSTRUCTIONS

When using
the PDP-II conditional branch instructions,
it
is
imperative that the correct choice be made between the signed and the
unsigned branches.
SIGNED

UNSIGNED

BGE
BLT
BGT
BLE

BHIS
BLO
BHI
BLOS

(BCC)
(BCS)

A common error is to use a signed branch (e.g., BGT)
when comparing
two memory addresses.
A problem occurs when the two addresses have
opposite signs;
that is, one address goes across the 16K
(100000(8))
boundary.
This type of coding error usually appears as a result of
reI inking at different addresses and / or a change in the size of the
program.

1-6

CHAPTER 2
SOURCE PROGRAM FORMAT

A source program is composed of a sequence of source lines, where each
line contains a
single assembly language statement.
Each line is
terminated by either a line feed or a vertical-tab character
(which
increments the line count by 1)
or a form-feed character (which
increments both the line count and page count by 1).
Since the MACll Interface automatically appends a line feed at the end
of every logical
input line, the user need not concern himself with
the statement terminator.
However, a carriage return character not
followed
by a statement terminator generates an error flag.
A legal
statement terminator not immediately preceded by a
carriage
return
causes the Assembler to insert a carriage return character for listing
purposes.
An assembly language line can contain up to
80(10)
characters
(exclusive of
the
statement terminator).
Beyond this limit, excess
characters are ignored and generate an error flag.

2.1

STATEMENT FORMAT

A statement can contain up to four
fields which are
identified by
order of appearance and by specified terminating characters.
The
general format of a MACll assembly language statement is:
label:

operator

operand

;comments

The label and comment fields are optional.
The operator and operand
fields are
interdependent;
either may be omitted depending upon the
contents of the other.
The Assembler interprets and processes these statements one by one,
generating one or more binary instructions or data words or performing
an assembly process.
A statement must contain one of these fields and
may contain all four types.
Blank lines are legal.
Some statements have one operand, for example:
CLR

while others have two,
MOV

#ERR,R2

An assembly language statement must be complete on
No continuation lines are allowed.

2-1

one

source

line.

SOURCE PROGRAM FORMAT

F: F UF I;~ I;~;~
F:FGFI(>(:

2.1.1

r~ I T
I{ F O
J i"i F'
,./iCl()

:':) B I T ~:;'!>

'II' M()~:; I \ , (J (:,I... UE

I;~EGE I;.::X:

;; YF~:; ,' ClI\ ,
; 1'·1 0, EF<F< UF;:,

1;~EI( F (U i:;:

nIe

'II'DEFFLU I F;:EGFI...G " i"l ODE
'lI' f/it ,::,I<" '·')(:;I.l..IF

E~F(

t ,E{~::; L I:: ::0<

; ~:;ET MODE "

Label Field

A label is a user-defined symbol which is assigned the value of the
current location counter
and entered
into the user-defined symbol
table.
The value of the label is absolute.
A label is a symbolic means of referring to a specific location within
a program.
If present, a label always occurs first in a statement and
must be terminated by a colon.
For example, if the current location
is absolute 100(8), the statement:
ABCD:

MOV A,B

assigns the value 100(8) to the label ABCD.
ABCD references location 100 (8) .

Subsequent

reference

More than one label may appear within a
single label
field:
each
label within the
field
has the same value.
For example, if the
current location counter
is 100(8),
the multiple labels
in the
statement:
ABC:

A7.7:

$00:

MOV A,B

cause each of the three labels ABC, $00, and A7.7 to be equated to the
value 100(8).
The first six characters of a label are significant.
An error code is
generated if more than one label share the same first six characters.
A symbol used as a label may not be redefined within the user program.
An attempt to
redefine a
label
results in an error flag in the
assembly listing.

2-2

SOURCE PROGRAM FORMAT
2.1.2

Operator Field

An operator field follows the label field in a statement, and may
contain a macro call, an instruction mnemonic, or an assembler
directive. The operator may be preceded by none, one or multiple
labels and may be followed by one or more operands and/or a comment.
Leading and trailing spaces and tabs are ignored.
When the operator is a macro call, the Assembler inserts the
appropriate code to expand the macro.
When the operator is an
instruction mnemonic, it specifies the instruction to be generated and
the action to be performed on any operand(s) which follow. When the
operator is an Assembler directive, it specifies a certain function or
action to be performed during assembly.
An operator is legally terminated by a space,
non-alphanumeric character (symbol component).

tab,

any

Consider the following examples:
MOV A,B

(space terminates the operator MOV)

MOV@A,B

(@ terminates the operator MOV)

When the statement line does not contain an operand or comment, the
operator is terminated by a carriage return followed by a line feed,
vertical tab or form feed character.
A blank operator field is interpreted as a .WORD
(see Section 5.3.2).

2.1.3

assembler

directive

Operand Field

An operand is that part of a statement which is manipulated by the
operator.
Operands may be expressions, numbers, or symbolic or macro
arguments (within the context of the operation).
When multiple
operands appear within a statement, each is separated from the next by
one of the following characters: comma, tab, space or paired angle
brackets around one or more operands (see Section 3.1.1). An operand
may be preceded by an operator, label or other operand and followed by
a comment.
The operand field is terminated by a semicolon when followed by a
comment, or by a statement terminator when the operand completes the
statement. For example:
LABEL:

MOV A,B

;COMMENT

The space between MOV and A terminates the operator field and begins
the operand field;
a comma separates the operands A and B; a
semicolon terminates the operand field and begins the comment field.
2.1.4

Comment Field

The comment field is optional and may contain any ASCII characters
except null, rubout, carriage return, line feed, vertical tab or form
feed. All other characters, even special characters with a defined
usage, are ignored by the Assembler when appearing in the comment
field.

2-3

SOURCE PROGRAM FORMAT
The comment field may be preceded by one, any,
none or all of
the
other
three field
types.
Comments must begin with the semicolon
character and end with a statement terminator.
Comments do not affect assembly processing or program execution,
but
are useful
in source listings for
later
analysis, debugging, or
documentation purposes.

2.2

FORMAT CONTROL

Horizontal or line formatting of the source program is controlled by
the space and tab characters.
These characters have no effect on the
assembly process unless they are embedded within a symbol, number,
or
ASCII texti
or unless they are used as the operator field terminator.
Thus, these characters can be used
to provide an orderly source
program.
A statement can be written:
LABEL:MOV(SP)+,TAGiPOP VALUE OFF STACK
or, using formatting characters, it can be written:
LABEL:

MOV (SP)+,TAG

iPOP VALUE OFF STACK

which is easier to read in the context of a source program listing.
The XVM Edit program can be used to achieve the desired format.
Vertical formatting, i.e., page size, is controlled by the
form
feed
character.
A page of n lines is created by inserting a form feed
(type the CTRL/ FORM keys on the keyboard) after
the nth line.
See
Section 5.1.5 for other methods of vertical formatting.

2-4

CHAPTER 3
SYMBOLS AND EXPRESSIONS

This Chapter describes the various components of
expressions:
the Assembler character set,
symbol
numbers, operators, terms and expressions.

3.1

legal
MACll
construction,

CHARACTER SET

The following characters are legal in MACll source programs:
1.

The letters A through Z.
Both upper and lower case letters
are acceptable although, upon input, lower case letters are
converted to upper case letters.
Lower case letters can only
be output by sending their ASCII values to the output device.
This conversion is not true for
.ASCII,
.ASCIZ,
I
(single
quote)
or
II
(double quote)
statements if .ENABL LC is in
effect.

The digits 0 through 9.

The characters.

(period or dot) and $ (dollar sign),

The special characters are as follows:
Character

Function

Designation

carriage return

formatting character

:::: :::: t

source statement terminators

vertical tab)

colon

label terminator

equal sign

direct assignment indicator

percent sign

tab

item or field terminator

space

item or field terminator
number sign

immediate expression indicator

3-1

SYMBOLS AND EXPRESSIONS
Character

Function

Designation
at sign

deferred addressing indicator

left parenthesis

initial register indicator

right parenthesis

terminal register indicator

comma

operand field separator

semi-colon

comment field indicator

left angle bracket

initial argument or expression
indicator

right angle bracket terminal argument or expression
indicator

plus sign

arithmetic addition operator or
auto increment indicator

minus sign

arithmetic subtraction operator
or autodecrement indicator

asterisk

arithmetic multiplication operator

slash

arithmetic division operator

ampersand

logical AND operator

exclamation

logical inclusive OR operator

double quote

double ASCII character indicator

single quote

single ASCII character indicator

up arrow

universal operator,
argument indicator

backslash

macro numeric argument indicator

3.1.1

Separating and Delimiting Characters

Reference is made in the remainder of the manual to legal separating
characters and legal argument delimiters. These terms are defined in
Tables 3-1 and 3-2.

3-2

SYMBOLS AND EXPRESSIONS
Table 3-1
Legal Separating Characters
Character

Defini tion

Usage

space

one or more spaces
and/or tabs

A space is a legal separator only
for argument
operands.
Spaces
within expressions are ignored.

comma

A comma is a legal separator for
both expressions and the argument
operands.

Table 3-2
Legal Delimiting Characters
Character

Definition

Usage

<... >

paired angle brackets

Paired angle brackets are used to
enclose an argument, particularly
when
that
argument
contains
separating
characters.
Paired
angle brackets may be used anywhere
in
a
program
to
enclose an
expression for treatment as a term.

t\ ... \

Up arrow construction
where the up arrow
character is followed
by an argument
bracketed by any
paired printing
characters.

This construction is equivalent in
function to the paired angle
brackets and is generally used only
where the argument contains angle
brackets.

Where argument delimiting characters are used, they must bracket the
first
(and, optionally, any following) argument(s). The character <
and the characters t \ , where \
is any printing character, can be
considered unary operators which cannot be immediately preceded by
another argument. For example:
.MACRO TEM <AB>C
indicates a macro definition with two arguments, while
.MACRO TEL C<AB>
has only one argument. The closing > , or matching character where the
up arrow construction is used, acts as a separator . The opening
argument delimiter does not act as an argument separator.
Angle brackets can be nested as follows:
<A<B>C >
which reduces to:
A<B>C
and is considered to be one argument in both forms.

3-3

SYMBOLS AND EXPRESSIONS
3.1.2

Illegal Characters

A character can be illegal in one of two ways:
1.

A character which is not recognized as an element of the
MACll character set is always an illegal character and causes
immediate termination of the current line at that point, plus
the output of an error flag in the assembly listing. For
example:
LABEL+-:

MOV

A,B

Since the backarrow is not a recognized character, the entire
line is treated as a:
.WORD

LABEL

statement and is flagged in the listing.
2.

3.1.3

A legal MACll character may be illegal in context.
Such
character generates a Q error on the assembly listing.

Operator Characters

Legal unary operators under MACll are as follows:
Unary
Operator Explanation
+

Example

plus sign

(positive
value
equivalent to A)

minus sign

-A

(negative,
val ue of A)

up arrow,
universal unary
operator (this
usage is described
in greater detail
in Section 5.4.2) .

AC24 (8)

(interprets the l's complement
value of 24 (8))

AD127

(interprets
number)

127

as a decimal

(interprets
number)

034

2's

complement,

ABIIOOOlll (interprets 11000111
binary value)
The unary operators as described above can be used
other in a term. For example:
-%5

tCt012

3-4

adjacent

octal
as

each

SYMBOLS AND EXPRESSIONS
Legal binary operators under MACll are as follows:
Binary
Operator

Example

Explanation

A+B
A-B
A*B
AlB
A&B

addition
subtraction
multiplication
division
logical AND
logical inclusive OR

*
I

(16-bit product returned)
(16-bit quotient returned)

AlB

All binary operators have the same priority.
Items can be grouped for
evaluation within an expression by enclosure in angle brackets.
Terms
in angle brackets are evaluated first, and
remaining operations are
performed left to right.
For example:
.WORD
.WORD
3.2

1+2*3
1+<2*3>

iIS 11 OCTAL
iIS 7 OCTAL

MACll SYMBOLS

There are three types of symbols:
permanent, user-defined and macro.
MACll maintains three types of symbol tables:
the Permanent Symbol
Table (PST), the User Symbol Table (UST) and the Macro Symbol Table
(MST) .
The PST contains all the permanent symbols.
The UST and MST
are constructed as the source program is assembledi
user-defined
symbols are added to the table as they are encountered.

3.2.1

Permanent Symbols

Permanent symbols consist of the instruction mnemonics (Appendix B.3)
and assembler directives
(Chapters
5 and 6, Appendix B.4).
These
symbols are a permanent part of the Assembler and need not be defined
before being used in the source program.

3.2.2

User-Defined and MACRO Symbols

User-defined symbols are those used as labels
(Section 2.1.1)
or
defined by direct assignment (Section 3.3).
These symbols are added
to the User Symbol Table as they are encountered during the first pass
of the assembly.
Macro symbols are those symbols used as macro names
(Section 6.1).
These symbols are added to the Macro Symbol Table as
they are encountered during the assembly.
User-defined and macro symbols can be composed of alphanumeric
characters, dollar
signs,
and periods onlYi
any other character is
illegal.
The following rules apply to the creation of
symbols:

user-defined

and

macro

The first character must not be a number.

Each symbol must be unique within the first six characters.

A symbol can be written with more than six legal characters,
but the seventh and subsequent characters are only checked

3-5

SYMBOLS AND EXPRESSIONS
for legality,
Assembler.
4.

and

are

not

otherwise

Spaces, tabs, and illegal characters
within a symbol.

recognized

must

not

the

embedded

A symbol
The value of a symbol depends upon its use in the program.
in the operator field may be anyone of the three symbol types. To
determine the value of the symbol, the Assembler searches the three
symbol tables in the following order:
1.
2.
3.

Macro Symbol Table
Permanent Symbol Table
User-defined Symbol Table

A symbol found in the operand field is sought in the
1.
2.

User-defined Symbol Table
Permanent Symbol Table

in that order.
operand field.

The Assembler never expects to find a macro name in an

These search orders allow redefinition of Permanent Symbol Table
entries as user-defined or macro symbols. The same name can also be
assigned to both a macro and a label.
All user-defined symbols are internal and must be defined
current assembly.

3.3

within

the

DIRECT ASSIGNMENTS

A direct assignment statement associates a symbol with a value.
When
a direct assignment statement defines a symbol for the first time,
that symbol is entered into the user symbol table and the specified
value is associated with it. A symbol ma y be redefined by assigning a
new value to a previously defined symbol. The latest assigned value
replaces an y previous value assigned to a symbol.
The general format for a direct assignment statement is:
symbol = expression
Symbols tak e on the absolute attribute of their
For example:
A

;THE SYMBOL A
;VALUE l.

defining
IS

expression.

EQUATED

B= A-l&MASKLOvl

;THE SYMBOL B IS EQUATED TO THE
;VALUE OF THE EXPRESSION.

D = 3

;THE SYMBOL D IS EQUATED TO 3.

MOV

#l ,ABLE

THE

;LABELS C AND E ARE EQUATED TO THE
;LOCATION OF THE MOV COMMAND.

3-6

SYMBOLS AND EXPRESSIONS
The following conventions apply to direct assignment statements:
1.

An equal
sign
(=)
must separate the
expression defining the symbol value.

A direct assignment statement is usually placed
in the
operator field and may be preceded by a label and followed by
a comment.

Only one symbol can be defined by anyone
statement.

Only one level of forward referencing is allowed.

Example of two levels of forward referencing

Y
Z

Z
1

symbol

direct

from

the

assignment

(illegal):

X and Yare both undefined
throughout pass 1.
X is undefined
throughout pass 2 and causes a U error flag in the assembly listing.

3.4

The eight general registers of the PDF-ll are numbered 0 through 7 and
can be expressed in the source program as:
%0
%1

%7
where the digit indicating the specific register can be replaced
by
any legal term which can be evaluated during the first assembly pass.
It is recommended that the programmer create and
use
symbolic names
for all register references.
A register symbol is defined in a direct
assignment statement, among the first statements in the program.
The
defining expression of a
register
symbol must be absolute.
For
example:

000000
000001
000002
000003
000004
000005
000006
000006
000007
000007

RO=%O
Rl=%l
R2=%2
R3=%3
R4=%4
R5=%5
R6=%6
SP=%6
PC=%7
R7=%7

iREGISTER DEFINITION

The symbolic names assigned to the registers in the example above are
the conventional names used in all PDP-ll system programs.
Since

3-7

SYMBOLS AND EXPRESSIONS
these names are fairly mnemonic, it is suggested the user follow this
convention.
Registers 6 and 7 are given special names because of
their special functions, while registers 0 through 5 are given similar
names to denote their status as general purpose registers.
All register symbols must be defined before they are referenced.
forward reference to a register symbol is flagged as an error.

The % character can be used with any term or expression to specify a
register.
(A register expression less than 0 or greater than 7 is
flagged with an R error code.) For example:
CLR %3+1
is equivalent to
CLR %4
and clears the contents of register 4, while
CLR 4
clears the contents of memory address 4.
In certain cases a register can be referenced without the use of a
register symbol or register expressioni these cases are recognized
through the context of the statement. An example is shown below:
JSR 5,SUBR

3.5

iFIRST OPERAND FIELD MUST ALWAYS BE A REGISTER

LOCAL SYMBOLS

Local symbols are specially formatted symbols used as labels within a
given range. Use of local symbols can achieve considerable savings in
core space within the user symbol table. Core cost is one word for
each local symbol in each local symbol block, as compared with four
words of storage for each label stored in the user symbol table.
Local symbols provide a convenient means of generating labels for
branch
instructions,
etc.
Use of local symbols reduces the
possibility of multiply-defined symbols within a user program and
separates entry point symbols from local references. Local symbols
are not referenced from outside their local symbol block.
Local symbols are of the form n$ where n is a decimal integer from 1
to 127, inclusive, and can only be used on word boundaries. Local
symbols include:
1$
27$

59$
104$

Within a local symbol block, local symbols can be defined and
referenced.
However, a local symbol cannot be referenced outside the
block in which it is defined. There is no conflict with labels of the
same name in other local symbol blocks.

3-8

SYMBOLS AND EXPRESSIONS
Local symbols 64$ through 127$ can be generated automatically as a
feature of the macro processor
(see Section 6.3.5 for
further
details). When using local symbols, the user is advised to first
use
the range from 1$ to 63$.
A local symbol block is delimited in one of the following ways.:
1.

The range of a single local symbol block can consist of those
statements between two normally constructed symbol labels.
(Note that a statement of the form
LABEL=.
is a direct assignment, does not create a label in the strict
sense, and does not delimit a local range.)

The range of a single local symbol block can be delimited
with the
.ENABL LSB and
the
first
symbolic label.
The
default for LSB is off.

For examples of local symbols and local symbol blocks, see Figure 3-3.
Ln.
No.

Octal
Expansion

Source Code

Comments

000004 005020

eii:':
C:('iF:>

O()()():J.:?

J () 1 :::~:/ ",~

12 00020 005020

Ii·

1+:

i..

i".:t)) '("

ei i t,
C':i'! I

xc. fL.. I:···.!
::' h:
C(O,!::'

Hili

Figure 3-1
Assembly Source Listing of MACll Code
Showing Local Symbol Blocks

3-9

SYMBOLS AND EXPRESSIONS
The maximum offset of a local symbol from the base of its local symbol
blocks
is 128 decimal words.
Symbols beyond this range are flagged
with an A error code.

3.6

ASSEMBLY LOCATION COUNTER

The period (.) is the symbol for the assembly location counter.
When
used in the operand field of an instruction, it represents the address
of the first word of the instruction.
When used in the operand
field
of an assembler directive, it represents the address of the current
byte or word.
For example:
A:

MOV #.,RO

,. REFERS TO LOCATION A,
iI.E., THE ADDRESS OF THE
iMOV INSTRUCTION.

(# is explained in Section 4.9.)
At the beginning of each assembly pass,
the Assembler clears the
location counter.
Normally, consecutive memory locations are assigned
to each byte of binary data generated.
However, the location of
the
stored binary data may be changed by a direct assignment altering the
location counter .
. =expression
The expression defining the location counter must not contain
references or symbols that vary from one pass to another.

forward

Examples:
.=500
FIRST:

iSET LOCATION COUNTER TO ABSOLUTE
i500
MOV

.+lO,COUNT

. =520
SECOND:

iTHE ASSEMBLY LOCATION COUNTER NOW
iHAS A VALUE OF ABSOLUTE 520(8).
MOV

.,INDEX

. =.+20
THIRD:

iTHE LABEL FIRST HAS THE VALUE 500(8)
i.+lO EQUALS 510(8).
THE CONTENTS OF
iTHE LOCATION 510(8) WILL BE DEPOSITED
iIN LOCATION COUNT .

iTHE LABEL SECOND HAS THE VALUE 520(8)
iTHE CONTENTS OF LOCATION 520(8), THAT
iIS, THE BINARY CODE FOR THE INSTRUCTION
iITSELF, WILL BE DEPOSITED IN LOCATION
iINDEX .
iSET LOCATION COUNTER TO ABSOLUTE 540 OF
iTHE PROGRAM SECTION .

. WORD 0

iTHE LABEL THIRD HAS THE VALUE OF
iABSOLUTE 540.

3-10

SYMBOLS AND EXPRESSIONS
Storage area may be reserved by advancing the location counter.
For
example,
if the current value of the location counter is 1000, the
direct assignment statement
.=.+100
reserves 100(8) bytes of storage
instruction is stored at 1100.

3.7

space

the

The

program.

NUMBERS

The MACll Assembler assumes all numbers in the source program are
to
be interpreted in octal radix unless otherwise specified.
The assumed
radix can be altered with the .RADIX directive (see Section 5.4.1)
or
individual numbers can be treated as being of decimal, binary, or
octal radix (see Section 5.4.2).
Octal numbers consist of the digits 0 through 7 only.
A number not
specified as a decimal number and containing an 8 or 9 is flagged with
an N error code and treated as a decimal number.
Negative numbers are preceded by a minus sign
(the
Assembler
translates them into 2's complement form).
Positive numbers may be
preceded by a plus sign, although this is not required.
A number which is too large to fit
(177777 <n)
is
into 16 bits
truncated from the left and flagged with a T error code in the
assembly listing.

3.8

TERMS

A term is a component of an expression.
following:

A term

may

one

16-bit

the

A number, as defined in Section 3.7, whose
used.

value

A symbol, as defined earlier in the chapter.
Symbols
interpreted according to the following hierarchy:

are

a period causes the value of the current location counter
to be used.

a permanent symbol whose basic value is
arguments (if any) are ignored.

an undefined symbol is assigned a value
inserted in the user-defined symbol table.

used
of

and
zero

whose
and

An ASCII conversion using either an apostrophe followed by a
single ASCII character or a double quote followed by two
ASCII characters which results in a word containing the 7-bit
ASCII value of the character (s) .
(This construction is
explained in greater detail in Section 5.3.3.)

A term may also be an expression or term
brackets.
Any quantity enclosed
in

3-11

enclosed
in angle
angle brackets is

SYMBOLS AND EXPRESSIONS
evaluated before the remainder of the expression in which
it
is found.
Angle brackets are used to alter the left to right
evaluation of expressions (to differentiate between A*B+C and
A*<B+C » or to apply a unary operator to an entire expression
(-<A+B > , for example).

3.9

EXPRESSIONS

Expressions are combinations of terms joined together
by binary
operators and which reduce to a 16-bit value.
The operands of a .BYTE
directive (see Section 5.3.1) are evaluated as word expressions before
truncation to
the low-order eight bits.
Prior to truncation, the
high-order byte must be zero or all ones (when byte value is negative,
the sign bit is propagated) .
Expressions are evaluated left to right with no operator hierarchy
rules
except that unary operators take precedence over
binary
operators.
A term preceded by a unary operator can be considered as
containing
that
unary
operator.
(Terms are evaluated,
where
necessary, before their use in expressions.) Multiple unary operators
are valid and are treated as follows:
-+-A
is equivalent to
-<+ <-A »
is
interpreted as a
A missing term, expression, or external symbol
zero.
A missing operator
is
interpreted as +.
A Q error flag is
generated for each missing term or operator.
For example:
TAG:

LA 177777

is evaluated as
TAG:

LA+177777

with a Q error flag on the assembly listing line.
The value of an expression is the value of the absolute
expressionj
e.g.,

A
TAG:

5
20
MOV TAG+A,RO jSET RO TO 25 (8).

3-12

part

the

CHAPTER 4
ADDRESSING MODES

The program counter
always contains the
address of the next
word of the current

(PC, register 7 of the eight general
registers)
address of the next word to be fetched;
i.e., the
instruction to be executed, or the second or third
instruction.

In order to understand how the address modes operate and
how they
The
assemble,
the action of the program counter must be understood.
key rule is:
Whenever the processor
implicitly uses
the program counter to fetch a word from
memory,
the
program
counter
is
automatically incremented by two after
the fetch.
That is, when an instruction is fetched, the PC is incremented by two,
so
that it
is pointing
to
the
next word in memorYi
and, if an
instruction uses indexing (Sections 4.7, 4.8 and 4.11)
the processor
uses
the program counter to fetch the base from memory.
Hence, using
the rule above, the PC increments by two, and now points to
the next
word.
The following conventions are used in this Section:
1.

Let E be any expression as defined in Chapter 3.

Let R be a
register expression.
This
is any expression
containing a
term preceded by a
% character or a symbol
previously equated to such a term.
Examples:
RO
Rl
R2

%0
RO+l
1+%1

iGENERAL REGISTER 0
iGENERAL REGISTER 1
iGENERAL REGISTER 2

Let ER be a register expression or an expression in the range
o to 7 inclusive.

Let A be a general address specification which produces a
6-bit mode address field as described in Sections 3.1 and 3.2
of the PDP-II Processor Handbook.

The addressing specifications, A, can be explained in terms of E,
R,
and ER as defined above.
Each is illustrated with the single operand
instruction CLR or double operand instruction MOV.

4-1

ADDRESSING MODES
4.1

The register contains the operand.

4.2

Format for A:

Examples:

RO=%O
CLR RO

iDEFINE RO AS REGISTER 0
iCLEAR REGISTER 0

The register contains the address of the operand.

4.3

Format for A:

@R or

(ER)

Examples:

CLR @Rl
CLR (1)

iBOTH INSTRUCTIONS CLEAR
iTHE WORD AT THE ADDRESS
iCONTAINED IN REGISTER 1

AUTO INCREMENT MODE

The contents of the register are incremented immediately
used as the address of the operand.
(See note below.)
Format for A:

(ER) +

Examples:

CLR (RO)+
CLR (RO+3)+
CLR (2)+

Both JMP and JSR instructions using
non-deferred
autoincrement
mode,
auto increment the
register
before
its
use on the PDP-ll / 20 but afterwords on
the PDP-ll / 45 or
11 / 05.
In
double
operand
instructions of the addressing
form %R,(R)+ or %R,-(R) where the source
and destination registers are the same,
the source operand is evaluated as the
auto incremented
or
autodecremented
valuei
but the destination register, at
the
time it is used, still contains the
originally intended effective address.
In
the
following
two examples,
as
executed on the PDP-ll / 20, RO originally
contains 100.
RO, (0) +

iTHE QUANTITY 102 IS
iMOVED TO LOCATION 100

4-2

being

iEACH INSTRUCTION CLEARS
iTHE WORD AT THE ADDRESS
iCONTAINED IN THE
iSPECIFIED REGISTER AND
iINCREMENTS THAT
iREGISTER'S CONTENTS BY
iTWO.

NOTE

MOV

after

ADDRESSING MODES
MOV

RO,-(O)

;THE QUANTITY 76 IS MOVED
;TO LOCATION 76

The use of these forms should be avoided
as they are not compatible across the
PDP-ll family.
is printed with each instruction which is not
A Z error code
This is merely a
compatible among all members of the PDP-II family.
warning code.

4.4

AUTO INCREMENT DEFERRED MODE

The register contains the pointer to the address of the operand.
contents of the register are incremented after being used.

4.5

Format for A:

@(ER)+

Example:

CLR @(3)+

;CONTENTS OF REGISTER 3
;POINT TO ADDRESS OF WORD
;TO BE CLEARED
BEFORE
;BEING INCREMENTED BY TWO

AUTODECREMENT MODE

The contents of the register are decremented before being used as
address of the operand (see note under autoincrement mode) .

4.6

Format for A:

- (ER)

Examples:

CLR - (RO)
CLR -(RO+3)
CLR -(2)

the

CONTENTS OF
;DECREMENT
;REGISTERS 0, 3, AND 2 BY
USING AS
;TWO
BEFORE
;ADDRESSES OF WORDS TO BE
;CLEARED.

AUTODECREMENT DEFERRED MODE

The contents of the register are decremented before being used as
pointer to the address of the operand.

4.7

The

Format for A:

@- (ER)

Example:

CLR @- (2)

the

;DECREMENT CONTENTS OF
;REGISTER 2 BY TWO BEFORE
;USING AS POINTER TO
;ADDRESS OF WORD TO BE
;CLEARED.

INDEX MODE

The value of an expression E is stored as the second or third word of
the
instruction.
The effective address is calculated as the value of
E plus the contents of register ER.
The value E is called the base.

4-3

ADDRESSING MODES
Format for A:

E (ER)

Examples:

CLR X+2 (Rl)
CLR -2(3)

4.8

;EFFECTIVE ADDRESS IS X+2
;PLUS THE CONTENTS OF
; REGISTER l .
;EFFECTIVE
;ADDRESS IS -2 PLUS THE
;CONTENTS OF REGISTER 3.

INDEX DEFERRED MODE

An expression plus the contents of a register gives the pointer to the
address of the operand.

4.9

Format for A:

@E (ER)

Example:

CLR @14(4)

;IF REGISTER 4 HOLDS 100
;AND LOCATION 114 HOLDS
;2000, LOCATION 2000 IS
;CLEARED.

IMMEDIATE MODE

The immediate mode allows the operand
itself to be stored as the
second or
third word of the
instruction.
It is assembled as an
autoincrement of register 7, the PC.
Format for A:

Examples:

MOV #100, RO
MOV #X, RO

;MOVE AN OCTAL 100 TO
;REGISTER O.
MOVE THE
;VALUE OF SYMBOL X TO
;REGISTER O.

The operation of this mode is explained as follows.
The statement MOV #100,R3 assembles as two words.

These are:

o1 2 7 0 3
o 001 0 0
Just before this instruction is fetched and executed, the PC points to
the
first word of the instruction.
The processor fetches the first
word and increments the PC by two.
The source operand mode
is 27
(autoincrement the PC).
Thus the PC is used as a pointer to fetch the
operand (the second word of the instruction) before being
incremented
by two, to point to the next instruction.
4.10

ABSOLUTE MODE

Absolute mode is the equivalent of immediate mode deferred.
@#E
specifies an absolute address which is stored in the second or third
word of the
instruction.
Absolute mode
is
assembled
as
an
auto increment deferred of register 7, the PC.
Format for A:

@#E

Examples:

MOV @#100,RO
CLR @#X

4-4

;MOVE THE VALUE OF THE
;CONTENTS OF LOCATION 100
;TO REGISTER O.
CLEAR
;THE CONTENTS OF THE
;LOCATION WHOSE ADDRESS
;IS X.

ADDRESSING MODES
4.11

RELATIVE MODE

Relative mode is the normal mode for memory references.
Format for A:

Examples:

CLR 100
MOV X,Y

iCLEAR LOCATION 100.
iMOVE CONTENTS OF
iLOCATION X TO LOCATION
iY.

Relative mode is assembled as index mode, using register 7, the PC, as
the
index register.
The base of the address calculation, which is
stored in the second or third word of the
instruction,
is not the
address of the operand (as in index mode), but the number which, when
added to the PC, becomes the address of the operand.
Thus,
the
base
is X-PC,
which is called an offset.
The operation is explained as
follows:
If the statement MOV 100,R3 is assembled at absolute location 20,
assembled code is:
Location 20:
Location 22:

the

a 1 6 7 a 3
a a a 054

The processor fetches the MOV instruction and adds two to
the PC so
that it points to location 22.
The source operand mode is 67i
that
is, indexed by the PC.
To pick up the base, the processor fetches the
word pointed
to by the PC and adds two to the PC.
The PC now points
to location 24.
To calculate the address of the source operand,
the
base is added to the designated register.
That is, BASE+PC=54+24=lOO,
the operand address.
Since the Assembler considers "." as the address of the first word
the instruction, an equivalent index mode statement would be:

MOV 100-.-4(PC} ,R3
This mode is called relative because the operand address is calculated
relative to
the current PC.
The base is the distance or offset (in
bytes) between the operand and the current PC.
If the operator
and
its operand are moved
in memory so that the distance between the
operator and data remains constant,
the
instruction will operate
correctly anywhere in core.
4.12

RELATIVE DEFERRED MODE

Relative deferred mode is similar to relative mode,
except that the
expression, E, is used as the pointer to the address of the operand.

4.13

Format for A:

Example:

MOV @X,RO

iMOVE THE CONTENTS OF THE
iLOCATION WHOSE ADDRESS IS
iIN X INTO REGISTER O.

TABLE OF MODE FORMS AND CODES

Each instruction takes at least one word.
Operands of the
first
six
forms listed below do not increase the length of an instruction.
Each
operand in one of the other modes, however, increases the
instruction
length by one word.
4-5

ADDRESSING MODES
Form
R
@R or (ER)
(ER)+
@(ER)+
- (ER)
@-(ER)

Mode
On
In
2n
3n
4n
Sn

Meaning
Register mode
Register deferred mode
Autoincrement mode
Autoincrement deferred mode
Autodecrement mode
Autodecrement deferred mode

where n is the register number.
Any of the following forms adds one word to the instruction length:
Form

Mode

Meaning

E (ER)
@E (ER)
#E
@#E
E
@E

6n
7n
27
37
67
77

Index mode
Index deferred mode
Immediate mode
Absolute memory reference mode
Relative mode
Relative deferred reference mode

where n is the register number.
Note that in
register 7 (the PC) is referenced.

the

last

four

forms,

NOTE

4.14

An alternate
form
for
@R is
(ER) .
However, the form @(ER) is equivalent to
@O(ER) .

The form @#E differs from the form E in
that the
second or
third word of the
instruction
contains
the
absolute
address of
the operand rather than the
relative distance between
the operand
and
the
PC.
Thus,
the
instruction
CLR @#100 clears absolute location 100
even
if
the
instruction is moved from
the point at which it was assembled.

BRANCH INSTRUCTION ADDRESSING

The branch
instructions are
I-word
instructions.
The high byte
contains
the op code and the low byte contains an 8-bit signed offset
(7 bits plus sign) which specifies the branch address relative to
the
PC.
The hardware calculates the branch address as follows:
1.

Extend the sign of the offset through bits 8-15.

Multiply the result by 2.
than a byte offset.

Add the result to the PC to form the final branch address.

This creates a word offset

rather

The Assembler performs the reverse operation to form the byte offset
from the specified address.
Remember that when the offset is added to
the
PC,
the
PC
is pointing
to
the word
following
the branch
instruction;
hence the factor -2 in the calculation.
Byte offset

= (E-PC) / 2 truncated to eight bits.
4-6

ADDRESSING MODES

Since PC

= .+2, we have
Byte offset

= (E-.-2)/2 truncated to eight bits.

The EMT and TRAP instructions do not use the low-order byte of the
word.
This allows information to be transferred to the trap handlers
in the low order byte.
If EMT or TRAP is followed by an expression,
the value is put into the low-order byte of the word.
However, if the
expression is too big (>377(8)) it is truncated to eight bits and a T
error flag is generated.

4-7

CHAPTER 5
GENERAL ASSEMBLER DIRECTIVES

5.1

LISTING CONTROL DIRECTIVES

5.1.1

.LIST and .NLIST

Listing options can be specified
in the text of a MACll program
through the .LIST and .NLIST directives.
These are of the form:
.LIST arg
.NLIST arg
where:
arg represents one or more optional arguments.
When used without arguments, the listing directives alter the listing
level count.
The listing level count causes the listing to be
suppressed when it is negative.
The count is initialized to
zero,
incremented for each
.LIST and decremented
for each .NLIST.
For
example:
.MACRO LTEST
iLIST TEST
iA-THIS LINE SHOULD LIST
.NLIST
iB-THIS LINE SHOULD NOT LIST
.NLIST
iC-THIS LINE SHOULD NOT LIST
.LIST
iD-THIS LINE SHOULD NOT LIST (LEVEL NOT BACK TO ZERO)
.LIST
iE-THIS LINE SHOULD LIST (LEVEL BACK TO ZERO)
.ENDM
iLTEST
iCALL THE MACRO
iA-THIS LINE SHOULD LIST
.NLIST
. LIST
iE-THIS LINE SHOULD LIST (LEVEL BACK TO ZERO)
The primary purpose of the level count is to allow macro
expansions to be selectively listed and yet exit with the level
returned to the status current during the macro call.
The use of arguments with the listing directives does not affect
the level counti
however, use of .LIST and .NLIST can be used to
override the current listing control.
For example:

5-1

GENERAL ASSEMBLER DIRECTIVES
.MACRO XX

.LIST
X= .
. NLIST

iLIST NEXT LINE
iDO NOT LIST REMAINDER
iOF MACRO EXPANSION

.ENDM
.NLIST HE
XX
.LIST
X=.

iDO NOT LIST MACRO EXPANSIONS

iLIST NEXT LINE

Allowable arguments for use with the listing directives are as follows
(these arguments can be used singly or in combination):
Argument

Default

Function

SEQ

list

Controls the listing of source line sequence
numbers. Error flags are normally printed on
the line preceding the questionable source
statement.

LOC

list

Controls the listing of the location counter
(this
field
would
not
normally
be
suppressed) .

BIN

list

Controls
code.

BEX

list

Controls listing of binary extensionsi
that
is,
those locations and binary contents
beyond the first binary word
(per source
statement)
This is a subset of the BIN
argument.

SRC

list

Controls the listing of the source code.

COM

list

Controls the listing of comments. This is a
subset of the SRC argument and can be used to
reduce listing time and / or
space
where
comments are unnecessary.

list

Controls listing of macro
repeat range expansions.

list

Controls listing of macro
range expressions.

no list

Controls listing of macro expansions.

MEB

no list

Controls listing of macro expansion binary
code.
A .LIST MEB causes only those macro
expansion statements producing binary code to
be listed.
This is a subset of the ME
argument.

the

5-2

listing

generated

binary

definitions
calls

and

repeat

GENERAL ASSEMBLER DIRECTIVES

Argument

Default

CND

list

unsatisfied
Controls
the
listing
of
conditions and all .IF and .ENDC statements.
This argument permits conditional assemblies
to be listed without including unsatisfied
code.

no list

Control listing of all listing directives
having no arguments (those used to alter the
listing level count).

TOC

list

Control listing of tables of contents on pass
1
of
the
assembly
(see Section 5.1.4
describing the .SBTTL directive).
The full
assembly listing is printed during pass 1 of
the assembly.

TTM

Teletype
mode

Controls listing output format.
The TTM
argument (the default case)
causes output
lines to be truncated
to 72 characters.
Binary code is printed with the
binary
extensions below the first binary word.
The
alternative (.NLIST TTM) to Teletype mode
is
line printer mode, which is shown in Figure
5-1.

SYM

list

Function

Controls the listing of the symbol table
the assembly.

for

An example of an assembly listing is shown in Figure 5-1.

5.1.2

Page Headings

The MACII Assembler outputs each page in the format
shown in Figure
5-1, Line Printer Listing.
On the first line of each listing page the
Assembler prints (from right to left):
1.

title taken from .TITLE directive.

assembler version identification

page number.

The second line of each listing page contains the
specified in the last encountered .SBTTL directive.
5.1.3

subtitle

text

.TITLE

The .TITLE directive is used to assign a name to the listing output.
The name
is the first symbol following the directive and must be six
Radix-50 characters or less (any characters beyond the first
six are
ignored).
Non-Radix 50 characters are not acceptable.
For example:
.TITLE

PROG TO PERFORM DAILY ACCOUNTING

causes the listing output of the assembled program to be named
PROG
(this name
is distinguished from the filename of the binary output
specified in the command string to the Assembler).

5-3

GENERAL ASSEMBLER DIRECTIVES
PIRt:X.149
MACll XVM V1AOOO PAGE 29
LINt: PRINTt:R DKIVER FUR LP11/15
1
LP INTERRUPT t:NTRANCt:
2

3 007604
LPINT:
4 007604 042767
000100
1677u2
5 007612 004067
172222
6 007616 000004
7 007620 016700
177510
B 007624 001511

BIC

1100,LPCSR

;DISABLt: LP

JSR

RO,R.SAVt:

;SAVE REGISTERS

'*
"IUV

LP-2,KO

;fASK CUDt:
;GET TCB POINTt:k

LPXT
Tsr

LPCSR

It' ITS ALREADY I:lEEN STOPPED BY
A STOP 1/0 Rt:QUES'f.
;CHt:CK fLlR ERROR

1:l1~ 1

CLR

LPERR
LP.CL

;tt:S
;CLt:AR UU'f ANY Pt:NDING TIMER Rt:QUEST rOR US.

ISTB

LPCSR

;IS f'RIN'fER CURRENTLY GOING?

BPL
TSTB

LPS'flL
LP'fAB

IrES:
fOHGEr :HAR FUR NU.
;IN TAb EXPANSION TD SPACt:S?

BMI
Dt:C

'IS

LPBTCl

;Yt:S
;Dt:CH :::HAR COU'H

5$
@LPl3u,'f

;wENT TO -1, MAKE CH III FINISH LINt:
;4INUS BYf~ IS fAB EXPANSIUN CLlUNf

6$
@Lf'BUFf',LPBUF

;IS ONt:, GU St:f UP
:SfICK CrlAK INfLl LINE PHINTt:R dUFt'ER

;IGNUR~

10 07626 005"167
167662
11 u7632 1004~4
12 07634 005067
171560
13 07640
LPLOP:
14 07640 105767

INf~RRUPT

1676~0

15 07644 100043
16 07646 105767
000342
17 076~2 100421
18 07654 005367
000332
19 07660 100424
LU 07662 105777
U00322
21 07b66 lU0400
22 07670 117767
000314
167620
23 07676 005267
0003U6
24 07702 000756
25
26 07704 117767 bS:
00u300
000302
27 07712 005267
000272
28 07716 105267 4$:
000272
29 07722 112767
000040
167566
30 07730 000743
31 07732 105767 5$:
000260
32 07736 001403
33 07740 116767

d~I

ISla
B~I

MUVS
INC

;MOVt: PUIN'ft:R ILl Nt:XT CHAk

LPLOP

;GU LJU

MOVB

@LPBUt'f,LPTAB

;S£T UP fAb COUNT (MINUS, A LA 15)

INC

LPBUFf'

INCB

LPTAB

;COIJNT A SPACt: fOR TbiS rAB

MOVB

HO, LPBUf

;SPACt: TO LINE PRINTER

BR
rSTH

LPLUP
LPWL

;GU DU Nt:XT
; I'1AGt: Ok ASC II

8t:Q
MUVB

LPEOL,LPBUF

;IMAGt:, DON'T FORCE <CR>
;ASC!l, HERE IS <CARRIAGE

Nr~XT

Figure 5-1
Example of MACll Line Printer Listing
(132-column line printer)

5-4

~ETURN>

GENERAL ASSEMBLER DIRECTIVES
If there is no .TITLE statement, the
first listing output is

default

name

assigned

the

.MAIN.
The first
tab or
space following
the
.TITLE directive is not
considered part of the listing output name or header text, although
subsequent tabs and spaces are significant.
If there is more than one .TITLE directive, the last .TITLE
in the program conveys the name of the listing output.

5.1.4

directive

.SBTTL

The .SBTTL directive is used to provide the elements for
a printed
table of contents of the assembly listing.
The text following the
directive is printed as the second line of each of the
following
assembly
listing pages until
the next occurrence of a
.SBTTL
directive.
For example:
.SBTTL CONDITIONAL ASSEMBLIES
The text
CONDITIONAL ASSEMBLIES
is printed as the second
listing pages.

line

each

the

following

assembly

During pass 1 of the assembly process, MACll automatically prints a
table of contents for the listing containing the line sequence number
and text of each .SBTTL directive in the program.
An example of the table of contents is shown in Figure 5-2.
Note that
the first word of the subtitle heading
is not limited to six
characters since it is not a module name.

5-5

GENERAL ASSEMBLER DIRECTIVES
MACRO

VIA

5712-

1
1
1

1416-

1
1

26364041485051596872747578798088929399103109-

1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1

114116135-

1
1
1

MACRO VIA
TABLE OF CONTENTS
SECTOR INITIALIZATION
SUBROUTINE CALL DEFINITIONS
PARAMETERS
ROLL DEFINITIONS
PROGRAM INITIALIZATION
ASSEMBLER PROPER
STATEMENT PROCESSOR
ASSIGNMENT PROCESSOR
OP CODE PROCESSOR
EXPRESSION TO CODE-ROLL CONVERSIONS
CODE ROLL STORAGE
DIRECTIVES
DATA-GENERATING DIRECTIVES
CONDITIONALS
LISTING CONTROL
ENABL/ DSABL FUNCTIONS
CROSS REFERENCE HANDLERS
LISTING STUFF
KEYBOARD HANDLERS
OBJECT CODE HANDLERS
LISTING OUTPUT
I / O BUFFERS
EXPRESSION EVALUATOR
TERM EVALUATOR
SYMBOL/ CHARACTER HANDLERS
ROLL HANDLERS
REGISTER STORAGE
MACRO HANDLERS
FIN

.SBTTL
Table of Contents text is taken from the text of each
directive.
The associated numbers are the page and line sequence
numbers of the .SBTTL directive.
Figure 5-2
Assembly Listing Table of Contents

5-6

GENERAL ASSEMBLER DIRECTIVES
5.1.5

Page Ejection

There are several means of obtaining a page eject in a MACll
listing:

assembly

After a line count of 58 lines, MACll automatically performs
a page eject to skip over page perforations on line printer
paper and to formulate terminal output into pages.

(or as the
A form feed character used as a line terminator
only character on a line) causes a page eject. Used within a
macro definition a form feed character causes a page eject.
A page eject is not performed when the macro is invoked.

More commonly, the .PAGE directive is used within the source
code to perform a page eject at that point. The format of
this directive is
. PAGE
This directive takes no arguments and causes a
top of the next page.

skip

the

Used within a macro definition, the .PAGE is ignored, but the
page eject is performed at each invocation of that macro.

5.2

FUNCTIONS:

.ENABL AND .DSABL DIRECTIVES

Several functions are provided by MACll through the .ENABL and .DSABL
directives.
These directives use 3-character symbolic arguments to
designate the desired function, and are of the forms:
.ENABL arg
.DSABL arg
where:
arg

is one of the legal symbolic arguments defined below.

The following table describes the symbolic
associated functions in the MACll language:
Symbolic
Argument

arguments

and

their

Function

CDR

The statement .ENABL CDR causes source columns 73 and
greater to be treated as comment. This accommodates
sequence numbers in card columns 72-80.

Enabling of this function causes the Assembler to
accept lower case ASCII input instead of converting it
to upper case.

LSB

Enable or disable a local symbol block. While a local
symbol block is normally entered by encountering a new
symbolic label, .ENABL LSB forces a local symbol block
which is not terminated until a label following the
.DSABL LSB statement is encountered. The default case
is .DSABL LSB.

5-7

GENERAL ASSEMBLER DIRECTIVES
PNC

The statement .DSABL PNC inhibits binary output until
an
.ENABL PNC
is encountered.
The default case is
.ENABL PNC.

An incorrect argument causes the directive containing it to be flagged
as an error.

5.3

DATA STORAGE DIRECTIVES

A wide range of data and data types can be
following directives and assembly characters:

generated

with

the

The .BYTE directive is used to generate successive bytes of data.
directive is of the form:

The

.BYTE
. WORD

"
.ASCII
.ASCIZ
.RAD50
tB
tD

These facilities are explained in the following Sections.

5.3.1

.BYTE

.BYTE exp

iWHICH STORES THE OCTAL EQUIVALENT
iOF THE EXPRESSION exp IN THE NEXT
iBYTE.

.BYTE expl,exp2, ...

iWHICH STORES THE OCTAL EQUIVALENTS
iOF THE LIST OF EXPRESSIONS IN
iSUCCESSIVE BYTES.

where a legal expression must have an absolute value
(or
contain a
reference to an external symbol) and must result in eight bits or less
of data.
The 16-bit value of the expression must have a
high-order
byte
(which is truncated) that is either all zeros or all ones.
Each
operand expression is stored
in a
byte of the object program.
Multiple operands are separated by commas and stored in successive
bytes.
For example:
SAM=5
.=410
.BYTE

tD48,SAM

i060 (OCTAL EQUIVALENT OF 48 DECIMAL)
iIS STORED IN LOCATION 410, 005 IS

iSTORED IN LOCATION 411.
If the high order byte of the expression equates to a value other than
or -1, it is truncated to the low-order eight bits and flagged with
a T error code.

5-8

GENERAL ASSEMBLER DIRECTIVES
If an operand following the .BYTE directive is null, it is interpreted
as a zero.
For example:
.=420
.BYTE "

5.3.2

iZEROES ARE STORED IN BYTES 420,
421, AND 422.

.WORD

The .WORD directive is used to generate successive words of data.
directive is of the form:

The

.WORD exp

iWHICH STORES THE OCTAL EQUIVALENT
iOF THE EXPRESSION exp IN THE NEXT
iWORD

.WORD expl,exp2, ...

iWHICH STORES THE OCTAL EQUIVALENTS
iOF THE LIST OF EXPRESSIONS IN
iSUCCESSIVE WORDS.

where a legal expression must result in sixteen bits or less of data.
Each operand expression is stored in a word of the object program.
Multiple operands are separated by commas and stored in successive
words.
For example:
SAL=O
.=500
.WORD 177535,.+4,SAL

iSTORES 177535, 506, AND 0 IN
iWORDS 500, 502, AND 504.

If an expression equates to a value of more than sixteen bits,
truncated and flagged with a T error code.

If an operand following the .WORD directive is null, it is interpreted
as zero.
For example:
.=500
Word
,5,

iSTORES 0, 5, AND 0 IN LOCATIONS 500

i502, AND 504.
A blank operator field (any operator not recognized as a macro call,
op-code, directive or semicolon) is interpreted as an implicit .WORD
directive.
Use of this convention is discouraged.
The first term of
the first expression in the operand field must not be an instruction
mnemonic or assembler directive unless preceded by a + or operator.
For example:
LABEL:

.=440
+MOV,LABEL

iTHE OP-CODE FOR MOV, WHICH IS 010000,
iIS STORED ON LOCATION 440.
;440 IS STORED IN LOCATION 442.

Note that the default .WORD directive occurs whenever
there is a
leading arithmetic or logical operator, or whenever a leading symbol
is encountered which is not recognized as a macro call, an instruction
mnemonic
or assembler directive.
Therefore,
if an instruction
mnemonic, macro call or assembler directive is misspelled,
the
.WORD
directive is assumed and errors will
result.
Assume that MOV is
spelled incorrectly as MOR:
MOR

A,B

5-9

GENERAL ASSEMBLER DIRECTIVES
Two error codes result: Q occurs because an expression operator is
missing between MOR and A, and a U occurs if MOR is undefined. Two
words are then generated: one for MOR A and one for B.

5.3.3

ASCII Conversion of One or Two Characters

The ' and " characters are used to generate text characters within the
source text. A single apostrophe followed by a character results in a
word in which the 7-bit ASCII representation of the character is
placed in the low-order byte and zero is placed in the high-order
byte. For example:
MOV

#'A,RO

results in the following sixteen bits being moved into RO:
8

101

octal ASCII value of A

The' character is never followed by a carriage return, null, rubout,
line feed or form feed.
(For another use of the' character, see
Section 5.3.6.)
STMNT:
GETSYM
BEQ
CMPB
BEQ
CMPB
SEQ

4$
@CHRPNT,#':
LABEL
@CHRPNT,#'=
ASGMT

iCOLON DELIMITS LABEL FIELD.

iEQUAL DELIMITS
iASSIGNMENT PARAMETER.

A double quote followed by two characters results in a word in which
the 7-bit ASCII representations of the two characters are placed. For
example:
MOV

#"AB,RO

results in the following word being moved into RO:

102

octal ASCII value of B

101

octal ASCII value of A

5-10

GENERAL ASSEMBLER DIRECTIVES
The" character is never followed by a carriage return, null,
line feed or form feed.
For example:

rubout,

iDEVICE NAME TABLE
DEVNAM:
DEVNKB:

5. 3. 4

.WORD
.WORD
. WORD
.WORD
. WORD
.WORD
.WORD
.WORD
.WORD
.WORD
. WORD

i RF DISK
iRK DISK
iRP DISK
iTTY KEYBOARD
iDECTAPE
iLINE PRINTER
iPAPER TAPE READER
iPAPER TAPE PUNCH
iCARD READER
iMAGTAPE
iTABLE'S END

"DF
"DK
"DP
"KB
"DT
" LP
"PR
"PP
"CR
"MT
0

. ASC II

7-bit
The .ASCII directive translates character strings into their
The format of the
.ASCII equivalents for use in the source program .
. ASCII directive is as follows:
.ASCII

/ character string/

where:
character
string

is a string of any acceptable printing ASCII
characters.
The string may not include null
(blank)
characters, rubout, carriage return,
line feed,
vertical tab, or
form
feed.
Nonprinting characters can be expressed in
digits of the current radix and delimited by
angle
brackets.
(Any
legal,
defined
expression
is
allowed
between
angle
brackets.)

these are delimiting characters and may be
any printing characters other
than
i, < ,
and = characters and any character within the
string.

As an example:

.ASCII /HELLO/

iSTORES ASCII REPRESENTATION OF THE
iLETTERS H,E,L,L,O IN CONSECUTIVE
iBYTES .

. ASCII ABC/<15><12>/DEF/

iSTORES A,B,C,15,12,D,E,F IN
iCONSECUTIVE BYTES .

. ASCII

iSTORES
iBYTES.

/<AB >/

<,A,B, >

CONSECUTIVE

The i and = characters are not illegal delimiting characters, but are
pre-empted by their significance as a comment indicator and assignment

5-11

GENERAL ASSEMBLER DIRECTIVES
operator, respectively.
For other than the
first group,
are treated as beginning a comment field.
For example:
ASCII string
Generated

Example

semicolons

Notes

.ASCII

;ABC; / DEF /

A B C D E F

Acceptable, but not a
procedure.

.ASCII

/ ABC / ;DEF;

A B C

; DEF;
is treated as a comment and
ignored.

.ASCII

/ ABC/ =DEF=

A B C D E F

Acceptable,
procedure.

.ASCII

=DEF=

but

not

recomm e nded

recommended

The assignment
. ASCII=DEF
is
is performed and a Q-error
the
generated upon encountering
second

5.3.5

.ASCIZ

The .ASCIZ directive is equivalent to the .ASCII directive with a zero
byte automatically inserted as the final character of the string.
For
example:
When a list or
text string has been created with a
.ASCIZ
directive,
a search for the null character can determine the end
of the list.
For example:

HELLO:

5.3.6

MOV
MOV
MOVB
BNE

#HELLO,Rl
#LINBUF,R2
(Rl)+,(R2)+
X

.ASCIZ

<15 >< 12 >/ MACll VIA/ <15> <12>

;INTRO MESSAGE

. RAD50

The .RAD 5 0 directive allows the user the capability to handle symbols
in Radix-50 coded form (this form is sometimes referred to as MOD40) .
Radix-50 form allows three characters to be packed into sixteen bits;
therefore,
any 6-character symbol can be held in two words.
The form
of the directive is:
.RAD50

/ string /

5-12

GENERAL ASSEMBLER DIRECTIVES
where:
delimiters can be any printing characters
other than the =, < , and; characters.

/
string

is a list of the characters to be converted
(three characters per word)
and which may
consist of the characters A through Z, 0
through 9, dollar ($), dot (.) and space ( ).
If there are fewer than three characters (or
if
the
last
set is fewer than three
characters)
they are
considered
to
be
left-justified
and
trailing
spaces are
assumed.
Illegal nonprinting characters are
replaced with a? character and cause an I
error flag to be set.
Illegal printing
characters set the Q error flag.

The trailing delimiter may be a
matching delimiter. For example:
.RAD50
.RAD50
.RAD50
.RAD50

carriage

return,

semicolon,

;PACK ABC INTO ONE WORD.
;PACK AB (SPACE) INTO ONE WORD.
;PACK 3 SPACES INTO ONE WORD.
;PACK ABC INTO FIRST WORD AND
;0 SPACE SPACE INTO SECOND WORD.

/ ABC
/ AB/

/ ABCD/

Each character is translated into its Radix-50 equivalent as indicated
in the following table:
Character
(space)
A-Z

Radix-50 Equivalent (octal)

1-32
33

0-9

34
36-47

Note that another character could be defined for
currently unused.

code

35,

The Radix-50 equivalents for characters 1 through 3 (Cl, C2,
combined as follows:
Radix 50 value

which

C3)

are

((Cl*50)+C2)*50+C3

For example:
Radix-50 value of ABC is ((1*50)+2)*50+3 or 3223
See Appendix A for a table to quickly determine Radix-50 equivalents.
Use of angle brackets is encouraged in the .ASCII, .ASCIZ, and
.RAD50
statements whenever leaving the text string to insert special codes.
For example:
.ASCII <101>

;EQUIVALENT TO .ASCII/A/

. RAD 5 0 / AB / <3 5 >

;STORES 3255 IN NEXT WORD

5-13

GENERAL ASSEMBLER DIRECTIVES
CHRl=l
CHR2=2
CHR3=3

.RAD50<CHRl><CHR2><CHR3>

5.4

iEQUIVALENT TO .RAD50/ABC/

RADIX CONTROL

5.4.1

.RADIX

Numbers used in a MACll source program are initially considered to be
octal numbers.
However,
the programmer has the option of declaring
the following radices:
2, 4, 8, 10
This is done via the .RADIX directive, of the form:
.RADIX n
where:
n

is one of the acceptable radices.

The argument to the .RADIX directive is always interpreted in decimal
radix.
Following any radix directive, that radix is the assumed base
for any number specified until the following .RADIX directive.
The default radix at the start of each program,
and
the
assumed if none is specified, is 8 (octal).
For example:

argument

.RADIX 10

iBEGINS SECTION OF CODE WITH DECIMAL RADIX

.RADIX

iREVERTS TO OCTAL RADIX

In general, it is recommended that macro definitions not contain nor
rely on radix settings from the .RAOIX directive.
The temporary radix
control characters should be used within a macro definition.
(to, to,
and tB are described in the following Section.) A given radix is valid
throughout a program until changed.
Where a possible conflict exists
within a macro definition or
in possible future uses of that code
module, it is suggested
that the
user
specify values using
the
temporary radix controls.

5.4.2

Temporary Radix Control:

to,

to, and tB

Once the user has specified a radix for a
section of code,
or
has
determined to use the default octal radix, he. may discover a number of
cases where an alternate radix is more convenient (particularly within
macro definitions).
For example, the creation of a mask word might
best be done in the binary radix.

5-14

GENERAL ASSEMBLER DIRECTIVES
MACll has three unary operators to provide a single interpretation
a given radix within another radix as follows:

(x is treated as being in decimal radix)
(x is treated as being in octal radix)
(x is treated as being in binary radix)

tDx
tOx
tBx
For example:
tD123
to 47
tB 00001101
to<A+3 >

Notice that while the up arrow and radix specification characters may
not be separated, the radix operator can be physically separated from
the number by spaces or tabs for formatting purposes.
Where a term or
expression is
to be
interpreted
in another
radix,
it should be
enclosed in angle brackets.
These numeric quantities may be used any place where a
is legal.

numeric

value

PAL-IIR contains a feature, which is maintained for
compatibility in
MACll,
allowing
a
temporary radix change from octal to decimal by
specifying a decimal
radix number with a
"decimal point".
For
example:
100.
1376.
128.

5.5

(144 (8))

(2540(8))
(200 (8) )

LOCATION COUNTER CONTROL

The four directives which control movement of the location counter are
.EVEN and .000 which move the counter a maximum of one byte, and .BLKB
and .BLKW which allow the user to specify blocks of a given number
of
bytes or words to be skipped in the assembly.

5.5.1

.EVEN

The
.EVEN directive ensures
that
the assembly location counter
contains an even memory address by adding one if the current address
is odd.
If the assembly location counter is even, no action is taken.
Any operands following a .EVEN directive are ignored.
The

.EVEN directive is used as follows:
.ASCIZ / THIS IS A TEST/
.EVEN

iASSURES NEXT STATEMENT
iBEGINS ON A WORD BOUNDARY .

. WORD XYZ

5-15

GENERAL ASSEMBLER DIRECTIVES
5.5.2

.000

The .000 directive ensures that the assembly location counter
by adding one if it is even.
For example:

odd

;CODE TO MOVE DATA FROM AN INPUT LINE
;TO A BUFFER
N=5

BUFF:

AGAIN:

;BUFFER HAS 5 WORDS

.000
.BYTE
. BLKW

;COUNT=2N BYTES
;RESERVE BUFFER OF N WORDS

MOV
MOV
MOVB
MOVB
BEQ
DEC
BNE

#BUFF,R2
#LINE,Rl
1(R2),RO
(Rl)+,(R2)+
DONE
RO
AGAIN

;ADDRESS OF EMPTY BUFFER IN R2
;ADDRESS OF INPUT LINE IS IN Rl
;GET COUNT STORED IN BUFF-l IN RO
;MOVE BYTE FROM LINE INTO BUFFER
;WAS NULL CHARACTER SEEN?
;DECREMENT COUNT
;NOT = 0, GET NEXT CHARACTER

CLRB

- (R2)

;OUT OF ROOM IN BUFFER, CLEAR LAST
;WORD

N*2

DONE:

LINE:

.ASCIZ

/ TEXT/

In this case, .000 is used to place the buffer byte count in the
preceding the buffer, as follows:
COUNT

byte

BUFF-2
BUFF

5.5.3

.BLKB and .BLKW

Blocks of storage can be reserved using the
.BLKB and
.BLKW
directives.
.BLKB is used to reserve byte blocks and .BLKW reserves
word blocks .
The two directives are of the form:
. BLKB

exp

.BLKW

exp

5-16

GENERAL ASSEMBLER DIRECTIVES
where:
exp

is the number of bytes or words to reserve.
If no
argument is present,
1 is the assumed default value.
Any legal expression which is completely defined at
assembly time and produces an absolute number is legal.

For example:
1
2
3
4
5
6
7

000000

PASS:

000002
000006
000006
000007
000010
8 00012
9

10
11
12
13
14
15

.BLKW
;NEXT GROUP MUST STAY TOGETHER
;SYMBOL ACCUMULATOR

SYMBOL: .BLKW
MODE:
FLAGS:
.BLKB
SECTOR: .BLKB
VALUE:
.BLKW
RELLVL: .BLKW
.BLKW

1
1
1
1
2

;FLAG BITS
; SYMBOL/EXPRESSIONS TYPE
;EXPRESSION VALUE

CLCNAM:
CLCFGS:
CLCSEC:
CLCLOC:
CLCMAX:

2
1
1
1
1

;CURRENT LOCATION COUNTER SYMBOL

00020
00024
00025
00026
00030

.BLKW
.BLKB
.BLKB
.BLKW
.BLKW

;END OF GROUPED DATA

The .BLKB directive has the same effect as
.=.+exp
but is easier to interpret in the context of source code.

5.6

TERMINATING DIRECTIVES

5.6.1

.END

The .END directive indicates the physical end of the
The .END directive is of the form:

source

program.

.END

exp

is an optional argument which,
if present,
indicates
the program entry point, i.e., the transfer address.

where:

At the conclusion of the first assembly pass,
END statement, MACll prints:

upon

encountering

the

END OF PASS 1
and attempts to reread the source file(s)
source file
is on a disk,
DECtape,

5-17

to perform pass 2.
If the
or magtape device no further

GENERAL ASSEMBLER DIRECTIVES
operator action is necessary.
If the source file is on paper tape an
lOPS
4 message
is printed;
the user is expected to reposition the
tape in the reader and type tR (for CONTINUE).

5.7

CONDITIONAL ASSEMBLY DIRECTIVES

Conditional assembly directives provide
the programmer
with the
capability to conditionally include or ignore blocks of source code in
the assembly process.
This technique is used extensively to allow
several variations of a program to be generated from the source
program.
The general form of a conditional block is as follows:
.IF cond,argument(s)

;START CONDITIONAL BLOCK
;RANGE OF CONDITIONAL
;BLOCK

.ENDC

;END CONDITIONAL BLOCK

where:
cond

is a condition which must be met if the block
is to be
included
in the assembly.
These
conditions are defined below.

argument(s)

are a function of the condition to be tested.

range

is the body of code which is included in
the
assembly or
ignored depending upon whether
the condition was met.

The following are the allowable conditions:

5-18

GENERAL ASSEMBLER DIRECTIVES
Conditions
COMPLEMENT

ARGUMENTS

ASSEMBLE BLOCK IF

expression

expression=O (or 1"0)

expression

expression>O (or <0 )

expression

expression<O (or

NDF

symbolic argument

symbol is defined (or
undefined)

macro-type argument

argument is a blank (or
not blank)

IDN

DIF

two macro-type
argument$ separated
by a comma

arguments identical
(or different)

expression

same as EQ/NE

expression

same as GT/LE

POSITIVE

~O)

NOTE
A macro-type argument is enclosed in
angle brackets or within an up-arrow
construction (as described in Section
6.3). For example:
<A,B,C>
~/ 124 /

For example:
.IF EQ

ALPHA+l

iASSEMBLE IF ALPHA+l=O

.ENDC
Within the conditions DF and NDF the
allowed to group symbolic arguments:

following

& logical AND operator
logical inclusive OR operator

For example:
.IF DF SYMI & SYM2

.ENDC
assembles if both SYMI and SYM2 are defined.

5-19

two

operators

are

GENERAL ASSEMBLER DIRECTIVES
5.7.1

Subconditionals

Subconditionals may be placed within conditional blocks to indicate:
1.

assembly of an alternate body of code when the condition of
the block indicates that the code within the block is not to
be assembled.

assembly of a
non-contiguous body of code within
conditional
block
depending
upon
the
result of
conditional test to enter the block.

unconditional assembly of a body of code within a conditional
block.

the
the

There are three subconditional directives, as follows:

Subcond i tional

Function

.IFF

The code following this statement up to
the next
subconditional or end of the conditional block is
included in the program providing the value of the
condition tested
upon entering
the conditional
block was false.

.IFT

.IFTF

The code following this statement up to
the next
subconditional or the end of the conditional block
is included in the program regardless of the value
of
the
condition
tested
upon entering the
conditional block.

The implied argument of the subconditionals is the value of the
condition upon entering
the conditional block.
Subconditionals are
used within outer
level conditional
blocks.
Subconditionals are
ignored within nested, unsatisfied condition blocks.
For example:
.IF
.IFF

SYM

iASSEMBLE BLOCK IF SYM IS DEFINED
iASSEMBLE THE FOLLOWING CODE ONLY IF
iSYM IS UNDEFINED .

. IFT

iASSEMBLE THE FOLLOWING CODE ONLY IF
iSYM IS DEFINED .

. IFTF

iASSEMBLE THE FOLLOWING CODE
iUNCONDITIONALLY .

. ENDC

5-20

GENERAL ASSEMBLER DIRECTIVES
.IF
.IF
.IFF

OF
OF

iASSEMBLY TESTS FALSE
iTESTS FALSE
iNESTED CONDITIONAL
iIGNORED

.IFT

iNOT SEEN

.ENDC

However,

.IF OF
.IF OF
.IFF

X
Y

iTESTS TRUE
iTESTS FALSE
iIS ASSEMBLED

iNOT ASSEMBLED

• 1FT

.ENDC

5.7.2

Immediate Conditionals

An immediate conditional directive is a means of writing a
I-line
conditional block.
In this form, no .ENDC statement is required and
the condition is completely expressed on the line containing
the
conditional directive.
Immediate conditions are of the form:
.IIF

cond, arg, statement

where:
cond

is one of the legal conditions defined
conditional blocks in Section 5.7.

arg

is the argument associated with the condition
specifiedi
that is,
either an expression,
symbol, or macro-type argument, as described
in Section 5.7.

statement

is the statement
condition is met.

For example:
.!IF

FOO,BEQ ALPHA

5-21

executed

for

the

GENERAL ASSEMBLER DIRECTIVES
this statement generates the code
BEQ

ALPHA

if the symbol Faa is defined.
A label must not be placed in the label field of the
.IIF
Any necessary labels may be placed on the previous line:
LABEL:
.IIF

statement.

FPP,BEQ,ALPHA

or included as part of the conditional statement:
• IIF

5.7.3

FOO,LABEL:

BEQ ALPHA

PAL-IIR Conditional Assembly Directives

In order to maintain compatibility with programs developed
under
PAL-IIR,
the
following
conditionals remain permissible under MACll.
It is advisable that further programs be developed
using
the
format
for MACll conditional assembly directives.
Directive
.IFZ or .IFEQ
.IFNZ or .IFNE
.IFL or . IFLT
.IFG or .IFGT
. IFLE
.IFGE
.IFDF
.IFNDF

Arguments
expression
expression
expression
expression
expression
expression
logical expression
logical expression

Assemble Block i f
expression=O
expression=O
expression<O
expression >O
expression < or =0
expression > or =0
expression is true (defined)
expression is false
(undefined)

The rules governing the usage of these directives are now the same as
for
the MACll conditional assembly directives previously described.
Conditional assembly blocks must end with the .ENDC directive and are
limited to a nesting depth of 16(10) levels (instead of the 127(10)
levels allowed under PAL-llR).

5-22

CHAPTER 6
MACRO DIRECTIVES

6.1

MACRO DEFINITION

It is often convenient in assembly language programming to generate a
recurring coding sequence with a single statement.
In order to do
this,
the desired coding sequence is first defined with dummy
arguments as a macro.
Once a macro has been defined, a single
statement calling the macro by name with a list of real
arguments
(replacing
the corresponding dummy arguments in the definition)
generates the correct sequence or expansion.

6.1.1

. MACRO

The first statement of a macro definition must be a .MACRO
The .MACRO directive is of the form:

directive.

.MACRO name, dummy argument list
where:
name

is the name of the macro.
This na~e is any legal
symbol.
The name chosen may be used as a label
elsewhere in the program.
represents any legal separator (generally, a comma
or space).

dummy
argument
list

zero, one, or more legal symbols which may appear
anywhere in the body of the macro definition, even
as a label.
These symbols can be used elsewhere
in
the
user
program with no conflicts of
definition.
Where more than one dummy argument is
used,
they are separated by any legal separator
(generally a comma).

A comment may follow the dummy argument list in a statement containing
a .MACRO directive.
For example:
.MACRO ABS A,B

;DEFINE MACRO ABS WITH TWO ARGUMENTS

A label must not appear on a .MACRO statement.
Labels are sometimes
used on macro calls,
but serve no function when attached to .MACRO
statements.

6-1

MACRO DIRECTIVES
6.1.2

.ENDM

The final statement of
directive of the form:

every

macro

definition

must

.ENDM

name

is an optional argument, being the name of
terminated by the statement.

the

macro

where:

For example:
.ENDM

(terminates the current macro definition)

.ENDM ABS

(terminates the definition of the macro ABS)

If specified, the symbolic name in the .ENDM statement must correspond
to that in the matching .MACRO statement. Otherwise, the statement is
flagged and processing continues.
Specification of the macro name in
the
.ENDM statement permits the Assembler to detect missing .ENDM
statements or improperly nested macro definitions.
The .ENDM statement may contain a comment field, but must not
a label.

contain

An example of a macro definition is shown below:
.MACRO TYPMSG MESSGE
JSR R5,TYPMSG
.WORD MESSGE
.ENDM

6.1.3

iTYPE A MESSAGE

.MEXIT

In order to implement alternate exit points from a macro (particularly
nested macros),
the .MEXIT directive is provided.
.MEXIT terminates
the current macro as though an .ENDM directive were encountered.
Use
of
.MEXIT bypasses the complications of conditional nesting and
alternate paths.
For example:
.MACRO

ALTR

.IF

EQ,N

N,A,B

iSTART CONDITIONAL BLOCK

.MEXIT
.ENDC

iEXIT FROM MACRO DURING CONDITIONAL BLOCK
iEND CONDITIONAL BLOCK

.ENDM

iNORMAL END OF MACRO

In an assembly where N=O, the .MEXIT directive
expansion.

6-2

terminates

the

macro

MACRO DIRECTIVES
Where macros are nested, a .MEXIT causes an exit to the next higher
level. A .MEXIT encountered outside a macro definition is flagged as
an error.

MACRO Definition Formatting

6.1.4

A form feed character used as a line terminator on a MACll source
statement
(or as the only character on a line) causes a page eject.
Used within a macro definition, a form feed character causes a page
eject. A page eject is not performed when the macro is invoked.
Used within a macro definition, the .PAGE directive is ignored, but
page eject is performed at invocation of that macro.

6.2

MACRO CALLS

A macro must be defined prior to its first reference.
of the general form:
label:

Macro calls are

name, real arguments

where:
label

represents an optional statement label.

name

represents the name of the macro specified in
the
.MACRO directive preceding the macro
definition.

real
arguments

are those symbols, expressions, and values
which replace the dummy arguments in the
. MACRO
statement.
Where more than one
argument is used, they are separated by any
legal separator.

Where a macro name is the same as a user label, the appearance of the
symbol
in the operation field designates a macro call, and the
occurrence of the symbol in the operand field designates a
label
reference.
For example:
ABS:

MOV @RO,Rl

;ABS IS USED AS A LABEL

BR ABS

;ABS IS CONSIDERED A LABEL

ABS #4,ENT,LAR

;CALL MACRO ABS WITH 3 ARGUMENTS

Arguments to the macro call are treated as character
usage is determined by the macro definition.

6-3

strings

whose

MACRO DIRECTIVES
6.3

ARGUMENTS TO MACRO CALLS AND DEFINITIONS

Arguments within a macro definition or macro call are separated from
other arguments by any of the separating characters described in
Section 3.1.1. For example:
. MACRO

REN A,B,C

REN

ALPHA,BETA,<Cl,C2>

Arguments which contain separating characters are enclosed in paired
angle brackets.
An up-arrow construction is provided to allow angle
brackets to be passed as arguments. Bracketed arguments are seldom
used in a macro definition, but are more likely in a macro call. For
example:
REN

<MOV X,Y>#44,WEV

This call would cause the entire statement:
MOV X,Y
to replace all occurrences of the symbol A in the macro definition.
Real arguments within a macro call are considered to be character
strings and are treated as a single entity until their use in the
macro expansion.
The up-arrow construction could have been used in the above macro call
as follows:
REN

t / MOV X,Y/ ,#44,WEV

which is equivalent to
REN

<MOV X,Y>,#44,WEV

Since spaces are ignored preceding an argument, they can be
increase legibility of bracketed constructions. The form:
REN

#44,WEVt/MOV X,Y/

however, contains only two arguments: #44 and
Section 3.1.1) because t is a unary operator.

6.3.1

used

WEV t/MOV X,Y/

(see

Macro Nesting

Macro nesting (nested macro calls), where the expansion of one macro
includes a call to another macro, causes one set of angle brackets to
be removed from an argument with each nesting level.
The depth of
nesting allowed is dependent upon the amount of core space used by the
program. To pass an argument containing legal argument delimiters to
nested macros, the argument should be enclosed in one set of angle
brackets for each level of nesting, as shown below.
. MACRO
LEVEL2
LEVEL2

LEVELl
DUMI
DUM2

DUMl,DUM2

6-4

MACRO DIRECTIVES
.ENDM
. MACRO LEVEL2
DUM3
ADD #10,RO
MOV RO, (Rl) +
.ENDM

DUM3

A call to the LEVELl macro:
LEVELl

« MOV X,RO»,«CLR RO »

causes the following expansion:
MOV X,RO
ADD #10,RO
MOV RO, (Rl) +
CLR RO
ADD #10, RO
MOV RO, (Rl) +
where macro definitions are nested (that is, a macro definition is
entirely contained within the definition of another macro) the inner
definition is not defined as a callable macro until the outer macro
has been called and expanded. For example:
.MACRO LVI A,B

.MACRO LV2 A

.ENDM
.ENDM
The LV2 macro cannot be called by name until after the first call to
the LVI macro.
Likewise, any macro defined within the LV2 macro
definition cannot be referenced directly until LV2 has been called.

6.3.2

Special Characters

Arguments may include special characters without enclosing
the
argument in a bracket construction if that argument does not contain
spaces, tabs, semi-colons, or commas. For example:
.MACRO PUSH ARG
MOV
AR.G, - (SP)
.ENDM

PUSH X+3(%2)
generates the following code:
MOV X+3(%2) ,-(SP)

6-5

MACRO DIRECTIVES
6.3.3

Numeric Arguments Passed as Symbols

When passing macro arguments, a useful capability is to pass a symbol
which can be treated by the macro as a numeric string. An argument
preceded by the unary operator backslash (\) is treated as a number in
the current radix.
The ASCII characters representing the number are
inserted in the macro expansionj
their
functions are defined
in
context.
For example:
8=0

.MACRO INC A,B
CNT
A, \ B
B=B+l
.ENDM
.MACRO CNT A,B
.WORD
JSEE SEC.6.3.6 FOR EXPLANATION OF 'B.
.ENDM

A'B:

INC

X,C

The macro call would expand to:
XO:

.WORD

A subsequent identical call to the same macro would generate:
Xl:

.WORD

and so on for later calls.
The two macros are necessary because
dummy value of B cannot be updated in the CNT macro.
In the
macro, the number passed is treated as a string argument.
(Where
value of the real argument is 0, a single 0 character is passed to
macro expansion.)

the
CNT
the
the

The number being passed can also be used to make source listings
somewhat clearer.
For example, versions of programs created through
conditional assembly of a single source can identify themselves as
follows:
.MACRO lOT SYM
.ASCII /SYH/
.ENDM
. MACRO OUT ARG
lOT OOSA'ARG
.ENDM

OUT

jASSUME THAT THE SYMBOL 10 TAKES
A UNIQUE TWO DIGIT VALUE FOR
jEACH POSSIBLE CONDITIONAL ASSEMBLY
JOF THE PROGRAM

iON

jWHERE OOSA IS THE UPDATE
jVERSION OF THE PROGRAM
jAND ARG INDICATES THE
jCONDITIONAL ASSEMBLY VERSION.

\ ID

The above macro call expands to:
.ASCII

/OOSAXX/

where XX is the conditional value of 10.
Two macros are necessary since the text delimiting characters in
the
.ASCII statement would inhibit the concatenation of a dummy argument.

6-6

MACRO DIRECTIVES
6.3.4

Number of Arguments

If more arguments appear
in the macro call
than
in the macro
definition,
the excess arguments are
ignored.
If fewer arguments
appear in the macro call than in the definition, missing arguments are
assumed
to be null
(consist of no characters).
The conditional
directives .IFB and .IFNB can be used within the macro to detect
unnecessary arguments.
A macro can be defined with no arguments.

6.3.5

Automatically Created Symbols

is a
MACll can be made to create symbols of the form n$ where n
decimal integer number such that 64<n <127. Created symbols are always
local symbols between 64$ and 127$.
(For a description of local
symbols,
see Section 3.5.)
Such local symbols are created by the
Assembler in numerical order;
i.e.:
64$
65$

126$
127$
Created symbols are particularly useful where a label is required
in
the expanded macro.
Such a label must otherwise be explicitly stated
as an argument with each macro call or the same label
is generated
with each expansion (resulting in a multiply-defined label).
Unless a
label is referenced from outside the macro, there is no reason for the
programmer to be concerned with that label.
The range of these local symbols extends between two explicit labels.
Each new explicit label causes a
new local
symbol block to be
initialized.
The macro processor creates a local symbol on each call of a macro
whose
definition
contains
a
dummy
argument
preceded
by
the? character.
For example:
. MACRO ALPHA
TST
A
BEQ
B
ADD
#5,A

A, ?B

B:
.ENDM
Local symbols are generated onl y where the real argument of the macro
call
is either null or missing.
If a real argument is specified in
the macro call, the generation of a
local
symbol
is
inhibited and
normal replacement is performed.
Consider the following expansions of
the macro ALPHA above.

6-7

MACRO DIRECTIVES
GENERATE A LOCAL SYMBOL FOR MISSING ARGUMENT:
ALPHA %1
TST
%1
BEQ
64$
ADD
#5,%1
64$:
DO NOT CREATE A LOCAL SYMBOL:
ALPHA
TST
BEQ
ADD

%2,XYZ
%2
XYZ
#5,%2

XYZ:
These Assembler-generated symbols are restricted to the first
(decimal) arguments of a macro definition.

6.3.6

sixteen

Concatenation

The apostrophe or single quote character
(')
operates as a
legal
separating character
in macro definitions.
An' character
which
precedes and/or follows a dummy argument
in a macro definition
is
removed and
the
substitution of the
real argument occurs at that
point.
For example:
A'B:

.MACRO DEF A,B,C
.ASCIZ /C/
.WORD
"A" 'B
.ENDM

When this macro is called:
DEF X,Y,<MACll>
it expands as follows:
XY:

.ASCIZ /MACll/
'X'y
.WORD

In the macro definition,
the
scan
terminates upon finding
the
f i r s t ' character.
Since A is a dummy argument, the' is removed.
The scan resumes with B,
notes B as another dummy argument and
concatenates the
two dummy arguments.
The third dummy argument is
noted as going into the operand of the .ASCIZ directive.
On the
next
line
(this example is purely for illustrative purposes) the argument
to .WORD is seen as follows:
The scan begins with a ' character.
Since
it is neither preceded nor
followed
by a dummy argument,
the ' character remains
in
the macro definition.
The
scan
then
encounters
the
second' character which
is followed
by a dummy
argument and is discarded.
The scan of the argument A terminated upon
encountering
the
second ' which is also discarded since it follows a
The next ' character is neither preceded nor followed
dummy argument.
by a dummy argument and
remains
in the macro expansion.
The

6-8

MACRO DIRECTIVES
last 'character
is followed
by another dummy argument and
discarded.
(Note that the
five' characters were necessary
generate two' characters in the macro expansion.)
Within nested macro definitions, multiple single quotes can
with one quote removed at each level of macro nesting.

6.4

.NARG,

is
to

used,

.NCHR, AND .NTYPE

These three directives allow the
user
to obtain the number of
arguments
in a macro call
(.NARG), the number of characters in an
argument (.NCHR), or the addressing mode of an argument (.NTYPE).
Use
of these directives permits selective modifications of a macro
depending upon the nature of the arguments passed.
The .NARG directive enables the macro being expanded to determine the
number of arguments supplied in the macro call, and is of the form:
label:

.NARG

symbol

label

is an optional statement label

symbol

is any legal symbol whose value is equated
to
the
number of arguments
in the macro call currently
being expanded.
The symbol can be used by itself or
in expressions.

where:

This directive can occur only within a macro definition.
The .NCHR directive enables a
program to determine
characters in a character string, and is of the form:
label:

.NCHR

symbol,

the

number

where:
label

is an optional statement label.

symbol

is any legal symbol which
is equated
to
the
number of characters in the specified character
string.
The symbol
is separated
from
the
character
string
argument
by
any
legal
separator.

is a string of printing characters which should
only be enclosed
in angle brackets if
it
contains a
legal separator.
A semi-colon also
terminates the character string.

This directive can occur anywhere in a MACII program.
The .NTYPE directive enables the macro being expanded to determine the
addressing mode of any argument, and is of the form:
label:

.NTYPE

symbol, arg

6-9

MACRO DIRECTIVES
where:
label

is an optional statement label.

symbol

is any legal symbol, the low-order 6-bits of which
are equated to the 6-bit addressing mode of the
argument. The symbol is separated from the argument
by a legal separator. This symbol can be used by
itself or in expressions.

arg

is any legal macro argument
defined in Section 6.3.

(dummy

argument)
An

This directive can occur only within a macro definition.
of .NTYPE usage in a macro definition is shown below:
.MACRO SAVE
.NTYPE SYM,ARG
.IF
EQ,SYM&70
MOV
ARG,TEMP
.IFF
MOV
#ARG,TEMP
.ENDC
.ENDM

6.5

example

ARG
;REGISTER MODE
;NON-REGISTER MODE

.ERROR and .PRINT

The .ERROR directive is used to output messages to the command output
device during assembly pass 2. A common use is to provide diagnostic
announcements of a rejected or erroneous macro call. The form of the
.ERROR directive is as follows:
label:

.ERROR

label

is an optional statement label.

expr

is an optional legal expression whose value is
output to the command device when the .ERROR
directive is encountered.
Where expr is not
specified, the text only is output to the command
device.

expr;text

where:

denotes the beginning of the
output.
text

text

string

is the string to be output to the command
The
text
string
is
terminated by
terminator.

device.
a line

Upon encountering a .ERROR directive anywhere in a MACll program,
Assembler outputs a single line containing:
1.

2.
3.
4.

the
the
the
the

sequence number of the .ERROR directive line,
current value of the location counter,
value of the expression if one is specified, and
text string specified.

6-10

the

MACRO DIRECTIVES
For example:
.ERROR

A;UNACCEPTABLE MACRO ARGUMENT

causes a line similar to the following to be output:
512

5642

000076

;UNACCEPTABLE MACRO ARGUMENT

This message is being used to indicate an inability of the subject
macro to cope with the argument A which is detected as being indexed
deferred addressing mode (mode 70) with the stack pointer (%6) used as
the index register.
The line is flagged on the assembly listing with a P error code.
The .PRINT directive is identical to .ERROR
flagged with a P error code.

6.6

INDEFINITE REPEAT BLOCK:

except

that

not

.IRP AND .IRPC

An indefinite repeat block is a structure very similar
to a macro
definition.
An
indefinite repeat is essentially a macro definition
which has only one dummy argument and is expanded once for every real
argument supplied.
An indefinite repeat block is coded in-line with
its expansion rather than being referenced by name as a macro
is
referenced.
An indefinite repeat block is of the form:
label:

.IRP

arg,<real arguments>

(range of the indefinite repeat)

.ENDM
where:
label

is an optional statement label.
A label may
not appear on any .IRP statement within
another macro definition,
repeat range or
indefinite repeat range, or on any .ENDM
statement.

arg

is a dummy argument which is successively
replaced with the real arguments in the .IRP
statement.

is a list of arguments to be used
in the
expansion of the indefinite repeat range and
enclosed
in angle brackets.
Each
real
argument
is
a string of zero or more
characters or a list of real
arguments
(enclosed
in angle brackets).
The real
arguments are separated by commas.

range

is the block of code to be repeated once for
each real argument in the list.
The range

6-11

MACRO DIRECTIVES
may contain macro definitions, repeat ranges,
or other indefinite repeat ranges.
Note that
only created symbols should be used as labels
within an indefinite repeat range.
An indefinite repeat block can occur either within or outside macro
definitions,
repeat ranges,
or indefinite repeat ranges.
The rules
for creating an indefinite repeat block are the same as for
the
creation of a macro definition (for example, the .MEXIT statement is
allowed in an indefinite repeat block).
Indefinite repeat arguments
f o llow the same rules as macro arguments.

1
2

.TITLE
.LIST
000000
000001
000002
000003
000004
000005
000006
000007
000006
000007
177776
177570
000000 012/00
000050

4
5
6
7
8

#TABLE,RO

.IRP

X, ( A,B,C,D,E,F >

MOV

X, (RO) +

.ENDM

12
13

RO= % 00
Rl= % 01
R2= % 02
R3= % 03
R4= % 04
R5= % 05
R6= % 06
R7= % 07
SP= % 06
PC= % 07
PSW= 0177776
SWR= 0177570
MOV

IRPTST
MD,MC,ME

00004 016720
00003 2

MOV

A, (RO) +

00010 016720
000030

MOV

B,(RO)+

00014 016720
000026

MOV

c, (RO) +

00020 016720
000024

MOV

0, (RO) +

00024 016720
000022

MOV

E, (RO) +

00030 016720
000020

MOV

F, (RO) +

.IRPC

X,ABCDEF

Figure 6-1
.IRP and IRPC Example
6-12

MACRO DIRECTIVES
14
15
16
17

18
19
20
21
22
23
24
25
26
27
28

.ASCII

Ixl

.ENDM
00034

101

.ASCII

00035

102

.ASCII

00036

103

.ASCII

00037

104

.ASCII

00040

105

.ASCII

00041

106

.ASCII

I AI
I BI
ICI
IDI
lEI
I FI

041101 A:
041502 B:
042103 C:
042504 D:
043105 E:
043506 F:
TABLE:

.WORD
.WORD
.WORD
.WORD
.WORD
. WORD
.BLKW

"AB
"BC
"CD
"DE
liEF
"FG
6

000001

.END

00042
00044
00046
00050
00052
00054
00056

Figure 6-1 (Cont.)
.IRP and .IRPC Example

A second type of indefinite repeat block is available which handles
character substitution rather than argument substitution.
The .IRPC
directive is used as follows:
label:

.IRPC

arg,string

(range of indefinite repeat)

.ENDM
On each iteration of the indefinite repeat range, the dummy argument
(arg)
assumes the value of each successive character in the string.
Terminators for the string are:
space, comma, tab, carriage return,
line feed, and semi-colon.

6.7

REPEAT BLOCK:

.REPT

Occasionally it is useful to duplicate a block of code a number of
times in-line with other source code. This is performed by creating a

6-13

MACRO DIRECTIVES
repeat block of the form:
label:

.REPT

expr

(range of repeat block)

.ENDM

JOR

.ENDR

where:
label

is an optional statement label. The .ENDR or
.ENDM
directive may not have a label. A .REPT statement
occurring within another repeat block, indefinite
repeat block, or macro definition may not have a
label associated with it.

expr

is any legal expression controlling the number of
times the block of code is assembled. Where expr <O,
the range of the repeat block is not assembled.

range

is the block of code to be repeated expr number of
times.
The range may contain macro definitions,
indefinite repeat ranges, or other repeat ranges.
Note that no statements within a repeat range can
have a label.

The last statement in a repeat block can be an .ENDM or
.ENDR
statement.
The .ENDR statement is provided for compatibility with
previous assemblers.
The .MEXIT statement is also legal within the range of a repeat block.

6-14

CHAPTER 7
OPERATING PROCEDURES

This MACll Assembler assembles one ASCII source file containing MACll
statements at a time into a single absolute binary output file.
The
output of the Assembler consists of an absolute binary file on a paper
tape,
and an assembly listing followed by the symbol table listing on
the device assigned to .DAT-12.

7.1

LOADING MACll

MACll is loaded under VXM/DOS by typing:

i MACll

(followed by a carriage return or altmode)

(Characters printed by the system are underlined to differentiate them
from characters pr inted by the
user.)
The Assembler responds by
identifying itself and its version number, followed
by a > character
to indicate readiness to accept a command input string:
HACll XVM Vnxnnn
~

7.2

COMMAND INPUT STRING

In response to the > printed by the Assembler,
the
user
types
the
switch options followed by the input filename;
the switch options and
the filename are separated by a '+' or underbar.
Command input can be
terminated by a carriage return to restart MACll, or by an altmode to
return to the monitor at the end of assembly.
>SW+FILNAM
where:

is the switch option(s);
can be null
(for
an
assembly with no output,) or 'B' (for binary output)
or 'L' (for listing) or both.

FILNAM

is the
input filename
from
.DAT -11.
Default
extension is 'SRC'.
The filename can consist of up
to six characters followed by a spacers)
and
not
more
than
a
3-character extension
(additional
characters cause the message 'NAME ERROR/TOO LONG'
to be printed on the command input device).
All of

7-1

OPERATING PROCEDURES
the legal printing characters can be used in any
order.
The first non-space character to be typed
after the first left-arrow (+) or underbar is
recognized as the first character of the filename.
Similarly, the first non-space character after the
filename
(other than carriage return or altmode) is
recognized as the first character of the extension.
Examples:
.?+FILNAM ..}

assembly with no output of a
'filnam SRC'; restart MACll

file

called

.?+FILNAM EXT..}

assembly with no output of a
'FILNAM EXT'; restart MACll .

file

called

.?B+FILNAM EXT (ALT) assemble 'FILNAM EXT' with an absolute binary
output to paper tape; return control to the
monitor at the end of the assembly.
~L+FILNAM

EXT (ALT) assemble 'FILNAM EXT' with a listing
to .DAT -12; return to the monitor.

>LB+Xl Y2 E~~.J

output

assemble 'XIY2 EOO with an absolute binary
output to paper tape and a listing output to
.DAT -12; restart MACll.

If an error is made in typing the command string, typing the RUBOUT
key erases the immediately-preceding character. Repeated typing of
the RUBOUT key erases one character for each RUBOUT up to the
beginning of the line. Typing CTRL/U erases the entire line. Both
can only be used if the command has not been terminated by a carriage
return or altmode.
A syntactical error detected in the command string causes the
Assembler
to print a? character.
The Assembler then reprints
the> character and waits for a new command string to be entered.
If
the input file is not found or the name and / or the extension is
illegal, the message:
NAME ERROR/TOO LONG
is printed.

7.3

PAPER TAPE SOURCES

If the source file is on disk, DECtape or magtape, no operator
intervention is necessary at the end of Pass 1. If, however, it is on
tape, an IOPS4 message will be printed on the console device at the
end of Pass 1; the operator must reposition the tape in the reader
and type tR to continue.

7-2

APPENDIX A
MACll CHARACTER SETS

A.l

ASCII CHARACTER SET

EVEN
PARITY
BIT

7-BIT
OCTAL
CODE

CHARACTER

REMARKS

000
001

NUL
SOH

002

STX

003

ETX

004

EOT

o
o

005

ENQ

1
1

006
007
010

ACK
BEL
BS

o
o

011
012

HT
LF

013
014

VT
FF

015

016

017

020
021

DLE
DCl

022

DC2

023

DC3

NULL, TAPE FEED, CONTROL/SHIFT/P.
START OF HEADING:
ALSO SOM, START
OF MESSAGE, CONTROL/A.
START OF TEXT; ALSO EOA, END OF
ADDRESS, CONTROL/B.
END OF TEXT;
ALSO EOM, END OF
MESSAGE, CONTROL/C.
END OF TRANSMISSION (END);
SHUTS
OFF TWX MACHINES, CONTROL/D.
ENQUIRY (ENQRY);
ALSO WRU,
CONTROL/E.
ACKNOWLEDGE;
ALSO RU, CONTROL/F
RINGS THE BELL.
CONTROL/G.
BACKSPACE;
ALSO FEO, FORMAT
EFFECTOR.
BACKSPACES SOME
MACHINES.
CONTROL/H.
CONTROL/I.
HORIZONTAL TAB.
LINE FEED OR LINE SPACE (NEW LINE) ;
ADVANCES PAPER TO NEXT LINE,
DUPLICATED BY CONTROL/J.
VERTICAL TAB (VTAB).
CONTROL/K.
FORM FEED TO TOP OF NEXT PAGE
(PAGE).
CONTROL/L.
CARRIAGE RETURN TO BEGINNING OF
LINE.
DUPLICATED BY CONTROL/M.
SHIFT OUT;
CHANGES RIBBON COLOR TO
RED.
CONTROL/N.
SHIFT IN;
CHANGES RIBBON COLOR TO
BLACK.
CONTROL/O.
DATA LINK ESCAPE.
CONTROL/B (DCO).
DEVICE CONTROL 1, TURNS TRANSMITTER
(READER) ON, CONTROL/Q (X ON) .
DEVICE CONTROL 2, TURNS PUNCH OR
AUXILIARY ON.
CONTROL/R (TAPE,
AUX ON) .
DEVICE CONTROL 3, TURNS TRANSMITTER
(READER) OFF, CONTROL/S (X OFF) .

o
o

A-I

MACll CHARACTER SETS
0

024

DC4

025

NAK

1
0

026
027

SYN
ETB

7-BIT
OCTAL
CODE

CHARACTER

REMARKS

CAN
EM
SUB
ESC
FS
GS
RS
US
SP

CANCEL (CANCL) . CONTROL/X.
END OF MEDIUM.
CONTROL/ Yo
SUBSTITUTE.
CONTROL/ Z.
ESCAPE.
CONTROL/SHIFT/K.
CONTROL/SHIFT/L.
FILE SEPARATOR.
CONTROL/SHIFT/M.
GROUP SEPARATOR.
CONTROL/ SHIFT/ N.
RECORD SEPARATOR.
UNIT SEPARATOR.
CONTROL/ SHIFT/ O.
SPACE.

EVEN
PARITY
BIT
0
1
1
1
1
0
0
1
1
0
0
1
0
1
1
0
0
1
1
0
1
0
0
1
0
1
1
0
1
0
0
1
1
0
0
1
0
1
1
0
1
0
0
1
0
1
1
0

030
031
032
033
034
035
036
037
040
041
042
043
044
045
046
047
050
051
052
053
054
055
056
057
060
061
062
063
064
065
066
067
070
071
072
073
074
075
076
077
100
101
102
103
104
105
106
107

DEVICE CONTROL 4, TURNS PUNCH OR
AUXILIARY OFF.
CONTROL/ T (AUX OFF) .
NEGATIVE ACKNOWLEDGE; ALSO ERR,
ERROR.
CONTROL/U.
SYNCHRONOUS FILE (SYNC) . CONTROL/V.
END OF TRANSMISSION BLOCK; ALSO
MEDIUM.
LOGICAL
END
OF
LEM,
CONTROL/ W.

#
$
%
&

ACCENT ACUTE OR APOSTROPHE.
(
)

0
1
2
3
4
5
6
7
8
9
;

<
>
?
@

A
B
C
D
E
F
G
A-2

MACll CHARACTER SETS
EVEN
PARITY
BIT

7-BIT
OCTAL
CODE

0
1
1
0
1
0
0
1
0
1
1
0
1
0
0
1
1
0
0
1
0
1
1
0
0

110

H
I

112
113
114
115
116
117
120
121
122
123
124
125
126
127
130
131
132
133
134
135
136
137
140

1
1
0
1
0
0
1
1
0
0
1
0
1
1
0
1
0
0
1
0
1
1
0
0
1
1

141
142
143
144
145
146
147
150
151
152
153
154
155
156
157
160
161
162
163
164
165
166
167
170
171
172

0
1
0
0

173
174
175
176

177

CHARACTER

III

REMARKS

K
L
M
N
0

P
Q

R
S
T
U
V
W

X
Y
Z

[

\
1
t

SHIFT/K.
SHIFT/L.
SHIFT/M.

ACCENT GRAVE.

a
b

c
d

e
f

9
h

i
j
k

1
rn
n
0

P
g
r

s
t
u

v
w
x

DEL

THIS CODE GENERATED BY ALTMODE.
THIS CODE GENERATED BY PREFIX KEY
(IF PRESENT).
DELETE, RUBOUT.

A-3

MAC 11 CHARACTER SETS
A.2

RADIX-50 CHARACTER SET
ASCII Octal
Equivalent

Character
space
A-Z
$

101

unused
0 = 9

Radix-50
Equivalent

- 132

44
56

- 32
33
34
35

= 71

= 47

The maximum Radix-50 value is, thus,
47*50(2) + 47*50 + 47 = 174777
The following table provides a convenient means of translating between
the ASCII character set and its Radix-50 equivalents.
For example,
given the ASCII string X2B, the Radix-50 equivalent is
(arithmetic
performed in octal) :
X
2
B
X2B

113000
002400
000002
115402
MACll CHARACTER SETS
Translation of ASCII Character Set
to Radix-50 Equivalents

Single Char.
or
First Char.

Second
Character

Third
Character

A
B
C

E
F
G

H
I
J
K

M
N
0
p

R
S
T
U
V

003100
006200
011300
014400
017500
022600
025700
031000
034100
037200
042300
045400
050500
053600
056700
062000
065100
070200
073300
076400
101500
104600
107700

E
F
G

H
I
J
K
L

M
N
0
P
Q

R
S
T
U
V

000050
000120
000170
000240
000310
000360
000430
000500
000550
000620
000670
000740
001010
001060
001130
001200
001250
001320
001370
001440
001510
001560
001630

A-4

E
F
G

H
I
J
K
L

M
N
0
P
Q

R
S
T
U
V

000001
000002
000003
000004
000005
000006
000007
000010
000011
000012
000013
000014
000015
000016
000017
000020
000021
000022
000023
000024
000025
000026
000027

MACll CHARACTER SETS
Single Char.
or
First Char.

X
y

Z
$

unused
0
1
2
3
4
5
6
7
8
9

113000
116100
121200
124300
127400
132500
135600
140700
144000
147100
152200
155300
160400
163500
166600
171700

Character

X
y

Z
$

unused
0
1
2
3
4
5
6
7
8
9

001700
001750
002020
002070
002140
002210
002260
002330
002400
002450
002520
002570
002640
002710
002760
003030

A-5

Character

z
$

unused

1
2
3
4
5
6
7
8
9

000030
000031
000032
000033
000034
000035
000036
000037
000040
000041
000042
000043
000044
000045
000046
000047

APPENDIX B
MACll ASSEMBLY LANGUAGE AND ASSEMBLER

B.l

SPECIAL CHARACTERS

Character

Function

form feed

Source line terminator

line feed

Source line terminator

carriage return

Formatting character

vertical tab

Source line terminator
Label terminator
Direct assignment indicator

tab

Item terminator
Field terminator

space

Item terminator
Field terminator

Immediate expression indicator

Deferred addressing indicator
Initial register indicator
Terminal register indicator

, (comma)

Operand field separator
Comment field indicator

Arithmetic addition operator or
auto increment indicator
Arithmetic subtraction operator or
autodecrement indicator

Arithmetic multiplication operator

B-1

MACll ASSEMBLY LANGUAGE AND ASSEMBLER
Function

Character

Arithmetic division operator

Logical AND operator
Logical OR operator
Double ASCII character indicator

Single ASCII line indicator

(apostrophe)

Assembly location counter

Initial argument indicator

Terminal argument indicator

Universal unary operator
Argument indicator

MACRO numeric argument indicator

B.2

ADDRESS MODE SYNTAX

n is an integer between a and 7 representing a register.
R is a
register expression, E is an expression, ER is either a register
expression or an expression in the range a to 7.

Address
Mode Name

Address
Mode Number

@R or (ER)

Deferred
Register

(ER)+

Autoincrement

The contents of the register
ER
are
specified
by
incremented after being used
as the address of the operand.

@(ER)+

Deferred
Autoincrement

ER contains the pointer to the
address of the operand.
ER is
incremented after use.

- (ER)

Autodecrement

The contents of register ER
are decremented before being
used as the address of the
operand.

@- (ER)

Deferred
Autodecrement

The contents of register ER
are decremented before being
used as the pointer to the
address of the operand.

Format

B-2

Meaning
contains
the
is a register

MACH ASSEMBLY LANGUAGE AND ASSEMBLER
Format

Address
Mode Name

Address
Mode Number

E (ER)

Index

E plus the contents of the
register specified, ER, is the
address of the operand.

@E(ER)

Deferred Index

gives
the
E added
to ER
pointer
to the address of the
operand.

Immediate

E is the operand.

@#E

Absolute

E is the
operand.

address

the

Relative

the
E is
operand.

address

the

Deferred
Relative

E is the pointer to the
ress of the operand.

add-

B.3

Meaning

INSTRUCTIONS

The instructions which follow are grouped according
they take and the bit patterns of their op-codes.

the

operands

In the instruction-type format specification,
are used:

following

symbols

OP
R

the

Instruction mnemonic
Register expression
Expression
Register expression or expression O<ER<7
General address specification

ER
A

In the representation of op-codes, the following symbols are used:

Source operand specified by a 6-bit address mode.

Destination operand specified by a
mode.

8-bit offset to a location (branch instructions).

Integer between 0 and
register.

6-bit

representing

address

general

Symbols used in the description of instruction operands are:
SE
DE

I I
(

....

)

Source Effective Address
Destination Effective address
Absolute value of
Contents of
Becomes

The condition codes in the processor status word (PS) are affected by
the instructions.
These condition codes are represented as follows:
N

Negative bit:

set if the result is negative

Zero bit:

set if the result is zero

8-3

MACII ASSEMBLY LANGUAGE AND ASSEMBLER
V

oVerflow bit:

set if the operation caused an overflow

Carry bit:

set if the operation caused a carry.

In the representation of the instruction's
codes, the following symbols are used:

o
1

effect

the

condition

Conditionally set
Not affected
Cleared
Set

To set conditionally means to use
the
instruction's result to
determine the state of the code (see the PDP-II Processor Handbook).
Logical operations are represented by the following symbols:

B.3.1

Inclusive OR
Exclusive OR
AND
(used over a symbol) NOT (i.e., lIs complement)

Double-Operand Instructions

Instruction type format:

Op A,A
Status Word
Condition Codes
N Z V C
Operation

Op-Code

Mnemonic

OlSSDD
llSSDD

MOV
MOVB

MOVe
MOVe Byte

(SE)

(DE)

02SSDD
12SSDD

CMP
CMPB

CoMPare
CoMPare Byte

(SE)-(DE)

03SSDD
13SSDD

BIT
BITB

BIt Test
BIt Test Byte

(SE)&(DE)

04SSDD
14SSDD

BIC
BICB

BIt Clear
BIt Clear Byte

(SE)&(DE)~DE

05SSDD
15SSDD

BIS
BISB

BIt Set
BIt Set Byte

(SE) ! (DE)~DE

06SSDD
16SSDD

ADD
SUB

ADD
SUBtract

(SE)+(DE)~DE

*
*

B.3.2

Stands for

(DE)-(SE)~

*
*

Single-Operand Instructions

Instruction-type format:

Op A
Status Word
Condition Codes

Op-Code

Mnemonic

005000
105000

CLR
CLRB

Stands for
CLear
CLear Byte

Operation
0 DE

B-4

MACll ASSEMBLY LANGUAGE AND ASSEMBLER
Status Word
Condition Codes
Operation
N Z V C

Op-Code

Mnemonic

005100
105100

COM
COMB

COMplement
COMplement Byte

(DE) DE

005200
105200

INC
INCB

INCrement
INCrement Byte

(OE)+l DE

005300
105300

DEC
OECB

DECrement
DECrement Byte

(OE)-l DE

005400
105400

NEG
NEGB

NEGate
NEGate Byte

(OE)+l DE

005500
105500

AOC
AOCB

ADd Carry
ADd Carry Byte

(OE)+(C) DE

005600
105600

SBC
SBCB

SuBtract Carry
SuBtract Carry Byte

(OE)-(C) DE

005700
105700

TST
TSTB

TeST
TeST Byte

(OE)-O DE

006000

ROR

ROtate Right

106000

RORB

ROtate Right
Byte

cD:

~ * * * *

006100

ROL

ROtate Left

cD --1

~ * * * *

106100

ROLB

ROtate Left
Byte

c=D --J

006200

ASR

Arithmetic
Shift Right

Arithmetic
Shift Right
Byte

Stands for

ro--

~ * * * *

even or odd byte

15 14

~*I

t ~~I

~2;

Z:/:o

even or odd byte

106200

ASRB

00630D

ASL

Arithmetic
Shift Left

106300

ASLB

Arithmetic
Shift Left
Byte

000100

JMP

JuMP

000300

SWAB

SWAp Bytes

006700

SXT

Sign eXTend

Q
c

even or odd byte

~:I

: (?(o * * * *

DE PC

*
DE if N bit
clear
-1 OE if N bit
is set

B-5

*
*

MACll ASSEMBLY LANGUAGE AND ASSEMBLER
Status Word
Condition Codes
FN FZ FV FC
Operation

Op-Code

Mnemonic

070700

NEGO

NEGate Double

-(FOE)

170400

CLRO

CLeaR Double

170500

TSTO

1706DO

ABSO

B.3.3

Stands for

FOE

TeST Ooubel

(FOE)-O FOE

make ABSolute

FOE

Operation

Operate Instructions

Instruction-Type format:

Op-Code

Mnemonic

Stands for

000000

HALT

The computer stops
all functions.

000001

WAIT

The computer stops
and waits for an
interrupt.

000002

RTI

ReTurn from
Interrupt

The PC and PS are
popped off the SP
stack:
((SP) )->-PC
(SP)+2->-SP
((SP)) ->-PS
(SP)+2->-SP
RTI is also used
to return from a
trap.

000005

RESET

Returns all I/O
devices to power-on
status.

000241

CLC

CLear Carry bit

O->-C

000261

SEC

SEt Carry bit

l->-C

000242

CLV

CLear oVerflow bit

O->-V

000262

SEV

SEt oVer flow bi t

l->-V

000244

CLZ

CLear Zero bit

O->-Z

000264

SEZ

SEt Zero bit

l->-Z

000250

CLN

CLear Negative bit

O->-N

000270

SEN

SEt Negative bit

l->-N

B-6

MACII ASSEMBLY LANGUAGE AND ASSEMBLER
Status Word
Condition Codes
Operation
N
Z
V C

Op-Code

Mnemonic

000243

CVC

Clear oVerflow and
Carry bits

O~V

000254

CNZ

Clear Negative and
Zero bits

O+N
O+Z

000257

CCC

Clear all
Condition Codes

O+N
O+Z
O+V
O+C

000277

SCC

Set all
Condition Codes

l+N
l+Z
l+V
l+C

000240

NOP

No OPeration

B.3.4

Stands for

Trap Instructions

Instruction-type format:

Op or Op E where 0 < E < 377(8)
*OP (only)

Stands for

Status Word
Condition Codes
Z V C
Operation
N

Op-Code

Mnemonic

000003

BPT

BreakPoint Trap

Trap to location
14.
Reserved for
system usage.

*000004

lOT

Input/Output Trap

Trap to location
20. This is used
to call system
routines.

104000104377

EMT

EMulator Trap

Trap to location
30. Reserved for
for system usage.

104400104777

TRAP

*
Trap to location
34.
This is used
to call any routine
desired by the
programmer.

B-7

MACll ASSEMBLY LANGUAGE AND ASSEMBLER
B.3.5

Branch Instructions

Instruction-type format:

Op E where -128(10)

Stands for

< (E-.-2) / 2 < 127(10)
Condition to be
met if branch
is to occur

Op-Code

Mnemonic

0004XX

BRanch always

OOlOXX

BNE

Branch if Not
Equal (to zero)

Z=O

0014XX

BEQ

Branch if EQual
(to zero)

Z=l

0020XX

BGE

Branch if
Greater than or
Equal (to zero)

V=O

0024XX

BLT

Branch if Less
than (zero)

V=l

0030XX

BGT

Branch if
Greater than
(zero)

V) =0

0034XX

BLE

Branch if Less
than or equal
(to zero)

V) =1

1000XX

BPL

Branch if PLus

N=O

1004XX

BMI

Branch if MInus

N=l

1010XX

BHI

Branch if
HIgher

Z=O

1014XX

BLOS

Branch if LOwer
or Same

Z=l

1020XX

BVC

Branch if
oVerflow Clear

V=O

1024XX

BVS

Branch if
oVerflow Set

V=l

1030XX

BCC
Branch if Carry
(or BHIS) Clear (or
Branch if
Higher or Same)

C=O

1034XX

BCS
Branch if Carry
(or 8LOS) Set (or Branch
if Lower

C=l

8-8

MACII ASSEMBLY LANGUAGE AND ASSEMBLER
B.3.6

Instruction type format:

Op-Code

Mnemonic

004RDD

JSR

Op ER,A
Status Word
Condition Codes
Operation
N Z V C

Stands for
Jump to SubRoutine

Push register on
the SP stack, put
the PC in the
register.
DE TEMP (TEMP=
temporary storage
register internal
to processor.)
(SP)-2 SP
(REG) (SP)
(PC) REG
(TEMP) PC

The following instruction is available only on the PDP-II/45:
074RDD

B.3.7

XOR

eXclusive OR

(R)

DE DE

Subroutine Return

Instruction type format:

Op-Code

Mnemonic

00020R

RTS

Op ER

Stands for
ReTurn from
Subroutine

Status Word
Condition Codes
Operation
N Z V C
Put register in
PC and pop old
contents from SP
stack into register

B-9

MACll ASSEMBLY LANGUAGE AND ASSEMBLER
B.4

ASSEMBLER DIRECTIVES

Form

Operation

Described
in Manual
Section

A single-quote character
(apostrophe) followed by one
ASCII character generates a
word containing the 7-bit
ASCII representation of the
character in the low-order
byte and zero in the high
order byte.

5.3.3

A double-quote character
followed by two ASCII
characters generates a word
containing the 7-bit ASCII
representation of the two
characters.

5.3.3

~ Bn

Temporary radix control;
causes the number n to be
treated as a binary number.

5.4.2

~Dn

Temporary radix control;
causes the number n to be
treated as a decimal number.

5.4.2

~On

Temporary radix control;
causes the number n to be
treated as an octal number .

5.4.2

. ASCII string

Generates a block of data
containing the ASCII
equivalent of the character
string (enclosed in
delimiting characters) one
character per byte .

5.3.4

. ASCIZ string

Generates a block of data
containing the ASCII
equivalent of the character
str ing (enclosed in
delimiting characters) one
character per byte with a
zero byte following the
specified string .

5.3.5

. 6LKB exp

Reserves a block of storage
space exp bytes long.

5.5.3

8-10

MACll ASSEMBLY LANGUAGE AND ASSEMBLER

FORM

Operation

Described
in Manual
Section

.BLKW exp

Reserves a block of storage
space exp words long.

5.5.3

.BYTE expl,exp2, ...

Generates successive bytes of
data containing the octal
equivalent of the expression(s)
specified.

5.3.1

.DSABL arg

Disables the assembler
function specified by the
argument.

5.2

.ENABL arg

Provides the assembler
function specified by the
argument.

5.2

.END
.END exp

Indicates the physical end
of source program.
An
optional argument specifies
the transfer address.

5.6.1

.ENDC

Indicates the end of a
conditional block.

5.7

.ENDM
.ENDM symbol

Indicates the end of the
current repeat block,
indefinite repeat block, or
macro.
The optional symbol,
if used, must be identical to
the macro name.

6.1.2

.ERROR exp,string

Causes a text string to be
output to the command device
containing the optional
expression specified and the
indicated text string.

6.5

.EVEN

Ensures that the assembly
location counter contains an
even address by adding 1 if
it is odd .

5.5.1

. IF cond,argl,arg2, ...

Begins a conditional block of
source code which is included
in the assembly only if the
stated condition is met
with respect to the
argument(s) specified.

5.7

.IFF

Appears only within a
conditional block and
indicates the beginning of a
section of code to be
assembled if the condition
tested false.

5.7.1

B-ll

MACll ASSEMBLY LANGUAGE AND ASSEMELER

Operation

Form

Described
in Manual
Section

.IFT

Appears only within a
conditional block and
indicates the beginning of
a section of code to be
assembled if the condition
tested true.

5.7.1

.IFTF

Appears only within a
conditional block and
indicates the beginning of
a section of code to be
unconditionally assembled.

5.7.1

.IIF cond,arg,statement

Acts as a l-line conditional
block where the condition is
tested for the argument
specified.
The statement
is assembled only if the
condition tests true.

5.7.2

.IRP sym, <argl,arg2, ... >

Indicates the beginning of
an indefinite repeat block
in which the symbol specified
is replaced with successive
elements of the real argument
list (which is enclosed in
angle brackets) .

6.6

. IRPC sym,string

Indicates the beginning of an
indefinite repeat block in
which the s y mbol specified
takes on the value of
suc c essive characters in the
character string.

6.6

.LIST
.LIST arg

Without an argument,
.LIST
increments the listing level
count by one.
With an
argument .LIST does not alter
the listing level count but
formats the assembly listing
according to the argument
specified.

5.1.1

.MACRO sym,argl,arg2, ...

Indicates the start of a
macro named sym containing
the dummy arguments specified.

6.1.1

.MEXIT

Causes an exit from the
current macro or indefinite
repeat block.

6.1. 3

.NARG symbol

Appears only within a macro
definition and equates the
specified symbol to the
number of characters in the
string (enclosed in
delimiting characters).

6.4

8-12

MACll ASSEMBLY LANGUAGE AND ASSEMBLER

Form

Operation

Described
in Manual
Section

.NCHR sym,string

Can appear anywhere in a
source program; equates the
symbol specified to the
number of characters in the
string (enclosed in
delimiting characters).

6.4

.NLIST
.NLIST arg

Without an argument, .NLIST
decrements the listing level
count by 1. With an argument,
.NLIST deletes the portion of
the listing indicated by the
argument.

5.1.1

.NTYPE sym,arg

Appears only in a macro
definition and equates the
low-order six bits of the
symbol specified to the
six-bit addressing mode of
the argument.

6.4

.000

Ensures that the assembly
location counter contains an
odd address by adding 1 if it
is even.

5.5.2

. PAGE

Causes the assembly listing
to skip to the top of the
next page.

5.1. 5

.PRINT exp,string

Causes a text string to be
output to the command device
containing the optional
expression specified and the
indicated text string.

6.5

.RADIX n

Alters the current program
radix to n, where n can be 2,
4, 8, or 10.

5.4.1

.RAD50 string

Generates a block of data
containing the Radix-50
equivalent of the character
string (enclosed in
delimiting characters).

5.3.6

.REPT exp

Begins a repeat block.
Causes the section of code
up to the next .ENDM or
or .ENDR to be repeated
exp times .

6.7

. SBTTL string

Causes the string to be
printed as part of the
assembly listing page header.
The string part of each .SBTTL
directive is collected into

5.1. 4

B-13

MACll ASSEMBLY LANGUAGE AND ASSEMBLER

Form

Operation

Described
in Manual
Section

a table of contents at the
beginning of the assembly
listing.
.TITLE string

Assigns the first symbolic
name in the string to the
object module and causes the
string to appear on each page
of the assembly listing.
Only
one .TITLE directive should
be issued per program.

5.1. 3

.WORD expl,exp2, .•.

Generates successive words
of data containing the octal
equivalent of the
expression(s) specified.

5.3.2

B-14

APPENDIX C
PERMANENT SYMBOL TABLE

PST

PERMANENT SYMBOL TABLE

1
2
3

.TITLE

MACll XVM
PST

PAGE 1

PERMANENT SYMBOL TABLE
DIGITAL EQUIPMENT CORPORATION

4
5
6
7
8
9

10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27

28
29
30

31
32
33
34
35
36
37
38
39
40
41
42
43

000020 DRl=
000100 DR2=

200
100

iDESTRUCTIVE REFERENCE IN FIRST
iDESTRUCTIVE REFERENCE IN SECOND

000020
000010
000004
000002

020
010
004
002

iDIRECTIVE REQUIRES EVEN LOCATION
iDIRECTIVE USES BYTE MODE
iCONDITIONAL DIRECTIVE
iMACRO DIRECTIVE

DFLGEV=
DFLGBM=
DFLCND=
DFLMAC=

.IIF DF X45,
XFLTG= 0
.IIF DF XMACRO, XSMCAL= 0
.MACRO
.IF NB
.IF DF
.MEXIT
.ENDC
.ENDC
.RAD50
.BYTE
.GLOBL
.BYTE
.WORD
.ENDM

OPCDEF NAME, CLASS, VALUE, FLAGS, COND
<COND>
COND

. MACRO
.IF NB
.IF DF
.MEXIT
.ENDC
.ENDC

DIRDEF NAME, FLAGS, COND
<COND >
COND

/NAME/
FLAGS+O
OPCL'CLASS
200+0PCL'CLASS
VALUE

C-l

PERMANENT SYMBOL TABLE
PST

PERMANENT SYMBOL TABLE

44
45
46
47
48
49
50
51

00000

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
33
34
35
36
39
40

000020
000030
000040
000110
000120
000130
000140
000150
000160
000170
000200
000210
000220
000230
000240
000250
000260
000270
000300
000310
000320
000330
000340
000350
000360
000370
000400
000420
000430
000440
000450
000470
000500
000510
000520
000550
000560

.GLOBL
.RAD50
.BYTE
.BYTE
.WORD
.ENDM

MACll XVM

PAGE 2

NAME
/. 'NAME/
FLAGS+O
0
NAME

PSTBAS:

;BASE
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF

<ADC
<ADCB
<ADD
<ASL
<ASLB
<ASR
<ASRB
<BCC
<BCS
<BEQ
<BGE
<BGT
<BHI
<BHIS
<BIC
<BICB
<BIS
<BISB
<BIT
<BITB
<BLE
<BLO
<BLOS
<BLT
<BMI
<BNE
<BPL
<BR
<BVC
<BVS
<CCC
<CLC
<CLN
<CLR
<CLRB
<CLV
<CLZ

C-2

>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,
>,

01,
01,
02,
01,
01,
01,
01,
04,
04,
04,
04,
04,
04,
04,
02,
02,
02,
02,
02,
02,
04,
04,
04,
04,
04,
04,
04,
04,
04,
04,
00,
00,
00,
01,
01,
00,
00,

005500,
105500,
060000,
006300,
106300,
006200,
106200,
103000,
103400,
001400,
002000,
003000,
101000,
103000,
040000,
140000,
050000,
150000,
030000,
130000,
003400,
103400,
101400,
002400,
100400,
001000,
100000,
000400,
102000,
102400,
000257,
000241,
000250,
005000,
105000,
000242,
000244,

DRI
DRI
DR2
DRI
DRI
DRI
DRI

DR2
DR2
DR2
DR2

DRI
DRI

PERMANENT SYMBOL TABLE
PST

PERMANENT SYMBOL TABLE

1
2

000570
000600

3
4
5
6
7
8
9
10

000630
000640
000650
000660
000670
000730
000740
000750
000760
000770
001000
001010
001230
001240
001320
001330
001360
001370

CMZ

12
13
14
15
16
17
18
19
20

MACll XVM

OPCDEF
OPCDEF
00
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF'
OPCDEF
OPCDEF
OPCDEF
OPCDEF

PAGE 3
<CMP > ,
<CMPB >,
000254,
<COM > ,
<COMB > ,
<DEC > ,
<DECB > ,
<EMT > ,
<HALT > ,
<INC > ,
<INCB > ,
<lOT > ,
<JMP > ,
<JSR > ,
<MOV > ,
<MOVB > ,
<NEG > ,
<NEGB > ,
<NOP > ,
<RESET>,

C-3

02,
02,

020000,
120000,

01,
01,
01,
01,
06,
00,
01,
01,
00,
01,

005100,
105100,
005300,
105300,
104000,
000000,
005200,
105200,
000004,
000100,
004000,
010000,
1l0000,
005400,
105400,
000240,
000005,

OS,
02,
02,
01,
01,
00,
00,

DRI
DRI
DRI
DRI
DRI
DRI
DRI
DR2
DR2
DRI
DRI

PERMANENT SYMBOL TABLE
PST

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17

18
19

PERMANENT SYMBOL TABLE

001400
001410
001420
001430
001440
001450
001470
001500
001510
001520
001530
001600
001610
002020
002050
002070
002100
002110
002140

MACll XVM

OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF
OPCDEF

PAGE 4
<ROL
<ROLB
<ROR
<RORB
<RTI
<RTS
<SBC
<SBCB
<SCC
<SEC
<SEN
<SEV
<SEZ
<SUB
<SWAB
<TRAP
<TST
<'I'STB
<WAIT

C-4

>,
>,
>,
>,
>,
>,
>,
>,
>,
>
>,
>,
>,
>,
>,
>,
>,
>,
>,

01,
01,
01,
01,
00,
03,
01,
01,
00,
00,
00,
00,
00,
02,
01,
06,
01,
01,
00,

006100,
106100,
006000,
106000,
000002,
000200,
005600,
105600,
000277,
000261,
000270,
000262,
000264,
160000,
000300,
104400,
005700,
105700,
000001,

DRI
DRI
DRI
DRI
DRI
DRI
DRI

DRI

PERMANENT SYMBOL TABLE
PST

1
2
3
4
5
6
7
8
9
10
II

12
13
14

15
16
17

18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33

PERMANENT SYMBCL TABLE

002160
002170
002210
002220
002230
002250
002260
002270
002300
002310
002320
002340
002350
002420
002430
002440
002450
002460
002470
002500
002510
002520
002530
002540
002550
002560
002570
002600
002610
002620
002630
002640
002660

MACll XVM

DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF

PAGE 5
<ASCII>,
<ASCIZ>,
<BLKB >,
<BLKW >,
<BYTE > ,
<DSABL > ,
<ENABL>,
<END > ,
<ENDC >,
<ENDM >,
<ENDR > ,
<ERROR > ,
<EVEN > ,
<IF
>,
<IFDF > ,
<IFEQ > ,
<IFF > ,
<IFG > ,
<IFGE > ,
< IFGT > ,
<IFL > ,
< IFLE > ,
<IFLT > ,
<IFNDF > ,
<IFNE > ,
<IFNZ > ,
<1FT > ,
<IFTF > ,
>,
<IFZ
<!IF > ,
<IRP > ,
<IRPC > ,
<LIST > ,

C-5

DFLGBM
DFLGBM
DFLGEV
DFLGBM

DFLCND
DFLMAC, XMACRO
DFLMAC, XMACRO
DFLCND
DFLCND
DFLCND
DFLCND
DFLCND
DFLCND
DFLCND
DFLCND
DFLCND
DFLCND
DFLCND
DFLCND
DFLCND
DFLCND
DFLCND
DFLCND
DFLMAC, XMACRO
DFLMAC, XMACRO

PERMANENT SYMBOL TABLE
PST
1
2
3
4
5
6

7
8
9
10
11
12
13

14
15
16
17
18
19
20
21
22
23

PERMANENT SYMBOL TABLE
002670
002700
002720
002730
002740
002750
002760
002770
003000
003010
003020
003030
003040
003050
003060
003070
003100
003100

MACll XVM

DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF
DIRDEF

<MACR >,
<MACRO>,
<MEXIT>,
<NARG >,
<NCHR >,
<NLIST >
<NTYPE>,
<ODD > ,
<PAGE >,
<PRINT>,
<RADIX>,
<RAD50>,
<REM > ,
<REPT >,
<SBTTL >,
<TITLE >,

DFLMAC, Xr-1ACRO
DFLMAC, XMACRO
XMACRO
XMACRO
XMACRO

DIRDEF

<WORD >,

DFLGEV

XMACRO

DFLGEV
DFLMAC, XMACRO

WRDSYM:

003110

PSTTOP:
000001

,TOP LIMIT
.END

C-6

•

PAGE 6

APPENDIX D
ERROR MESSAGE SUMMARY

D.l

MACll ERROR CODES

MACll error codes are printed
following
a
field of six asterisk
characters and on the line preceding the source line containing the
error.
For example:

******A
26 00236

000002'

.WORD REL1+REL2

The addition of two relocatable symbols is flagged as an A error.

Error Code

Meaning

Addressing
error.
An
address
within
the
instruction is
incorrect.
Also may indicate a
relocation
error.
This
message
does
not
necessarily reflect a coding error.

Bounding error.
Instructions or word data
being assembled at an odd address in memory.
location counter is updated by +1.

Doubly-defined symbol referenced.
Reference was
made to a symbol which is defined more than once.

End directive
generated. )

Illegal character detected.
Illegal characters
which are also non-printing are replaced by a ?
on the listing.
The character is then ignored.

Line buffer overflow;
i.e.,
input line greater
than 132 characters.
Extra characters on a line
(more than 72(10)) are ignored.

Multiple definition of a
label.
A label was
encountered which was equivalent (in the first six
characters) to a previously encountered label.

Number containing
missing.

D-l

not

found.

has

listing

decimal

are
The

point

ERROR MESSAGE SUMMARY
Error Code

Meaning

Op-code error.

Phase error.
A label's definition of value varies
from one pass to another.

Questionable syntax.
There are missing arguments
or
the
instruction scan was not completed or a
carriage return was not immediately followed by a
line feed, form feed, or vertical tab.

Truncation error.
A number generated more than 16
bits of significance or an expression generated
more than 8 bits of significance during the use of
the .BYTE directive.

Undefined
symbol.
An
undefined
symbol
encountered
during
the
evaluation
of
expression.
Relative to
the expression,
undefined symbol is assigned a value of zero.

was
an
the

Instruction which
is not compatible
members of the PDP-II family.

all

0-2

Directive out of context.

among

INDEX
Absolute mode, 4-4
Addition, 3-5
Addition operator, 3-2
Addressing, branch instruction,
4-6
Address modes, 1-4, 4-1, 6-9
syntax, B-2
Address, negative, 1-6
Ampersand (&), 3-2
AND operator, 3-2, 3-5
Angle brackets
2-3, 3-3,

«»,

5-13

Apostrophe ('), 3-2, 6-8
Arguments \"i thin a macro
definition, 6-4
ASCII character conversion, 5-10
ASCII character indicator, 3-2
ASCII characters, 2-3, A-l
.ASCII directive, 5-11
.ASCIZ directive, 5-12
Assembler directives, 2-3, 3-5,
B-10
Assemblies, conditional, 1-4
Assembly listing example
(figure), 5-4
Assembly listing table of
contents (figure), 5-6
Assembly location counter, 3-10,
5-15, 5-16
Asterisk (*), 3-2
At sign (@), 3-2
Autodecrement deferred mode, 4-3
Autodecrement mode, 4-3
Autoincrement deferred mode, 4-3
Autoincrement mode, 4-2

Backarrow (~) usage, 7-1
Backslash (~), 3-2, 6-6
Binary operators, 3-5, 3-12
Blank lines, 2-1
.BLKB directive, 5-16
.BLKW directive, 5-16
Branch instruction addressing,
4-6
Branch instructions, B-8
.BYTE directive, 5-8

Carriage return, 2-1, 3-1
Character deletion, 7-2
Characters,
ASCII, 2-3, A-l
delimiting, 3-3
illegal, 3-4
~ACll legal, 3-1

Characters (cont.),
Radix-50, A-4
separating, 3-3
special, B-1
Code, reentrant, 1-4
Code segment (figure), 1-3
Colon (:) usage, 2-2, 3-1
Comma (,), 2-3, 3-2, 3-3
Command input string, 7-1
Comments, 1-2, 2-3, 6-1
field indicator, 3-2
Concatenation, 6-8
Conditional assembly, 1-4
directives, 5-18
PAL-llR directives, 5-22
Conditional branch instructions,
1-6
Condition codes, B-3
Continuation lines, 2-1
Core Storage, 1-5, 3-8

Data generation, 5-9
Data storage directives, 5-8
Deferred addressing indicator,
3-2
Deletion of characters or lines,
7-2
Delimiting characters, 3-3
Direct assignment indicator, 3-1
Direct assignments, 3-6
Directives, assembler, 2-3, 3-5,
B-10
conditional, 5-18
immediate conditional, 5-21
MACRO, 6-1
PAL-llR conditional assembly,
5-22
subconditional, 5-20
terminating, 5-17
Dispatch table, 1-5
Division, 3-5
operator, 3-2
Double-operand instructions, B-4
Double quote ("), 3-2
.DSABL directive, 5-7

.ENABL directive, 5-7
.END directive, 5-17
.ENDM directive, 6-2
.ENDR statement, 6-14
.ERROR directive, 6-10
Error message summary, D-l
Errors, typing, 7-2
Equal sign (=), 3-1
Index-l

INDEX (Cont.)
.EVEN directive, 5-15
Exclamation (!), 3-2
Expression indicator, 3-2
Expressions, 3-12

Fields in statements, 2-1
comment, 2-3
label, 2-2
operand, 2-3
operator, 2-3
Field terminator, 3-1
Format control, 2-4
Form feed, 2-1, 3-1, 6-3
Forward referencing, 3-7

Hierarchy operator, 3-12

Location counter control, 5-15
Logical operations, B-4

.MACRO directive, 6-1
Macros,
calls, 6-3
definition formatting, 6-3
directives, 6-1
nesting, 6-4
numeric argument indicator, 3-2
symbols, 3-5
Mask word, 5-14
Message output, 6-10
.MEXIT directive, 6-2
.VillXIT statement, 6-14
Hinus sign (-), 3-2
Hode forms and codes, 4-5
Modes of address, 4-1
Modular programming, 1-1
Multiplication, 3-5
Multiplication operator, 3-2

Illegal characters, 3-4
.IFF directive, 5-20
.IFT directive, 5-20
.IFTF directive, 5-20
Immediate conditional directive,
5-21
Immediate expression indicator,
3-1
Immediate mode, 4-4
Indefinite repeat block:
.IRP
and . IRPC, 6-11
Index deferred mode, 4-4
Index mode, 4-3
Indicators, 3-2
Initial register indicator, 3-2
Instructions, 2-3, 3-5, B-3
conditional branch, 1-6
([igure), 1-3
Item terminator, 3-1

.NARG directive, 6-9
.NCHR directive, 6-9
Negative address, 1-6
Negative numbers, 3-11
Nested angle brackets, 3-3
Nested macros, 6-2, 6-4
.NLIST directives, 5-1
.NTYPE directive, 6-9
Null arguments, 6-7
Number of arguments in a macro
call, 6-7, 6-9
Number of characters in string,
6-9
Numbers, 3-11, 5-14
Number sign (#), 3-1
Numeric arguments, 6-6

Label field, 2-2
Label terminator, 3-1
Line deletion, 7-2
Line feed, 3-1
Line formatting, 2-4
Line printer listing (figure),
5-4
Line terminators, 2-1
.LIST directive, 5-1
Listing level count, 5-1
Loading MACll, 7-1
Local symbol blocks (Figure),
3-9
Local symbols, 3-8

Octal radix, 3-11
.000 directive, 5-16
Offset, 3-10, 4-6
l's Complement, 3-4
Op-codes, B-3
Operand field, 2-3, 3-2
Operands, B-3
Operate instructions, B-6
Operating procedures, 7-1
Operator field, 2-3
Operator hierarchy, 3-12
Operators, 3-2
OR operator, 3-2, 3-5
Output, 7-1
Index-2

INDEX (Cant.)
.PAGE directive, 5-7, 6-3
Page eject, 5-7, 6-3
Page headings, 5-3
PAL-llR conditional assembly
directives, 5-22
Paper tape sources, 7-2
Parameter assignments, 1-5
Parentheses (), 3-2
Pass 1, 7-2
PC register, 1-4
PDP-ll code segment (figure),
1-3
Percent sign (%), 3-1, 3-8
Period (.), 3-10
Permanent symbols, 3-5
Permanent symbol table, C-l
Plus sign (+), 3-2
Processor status word (PS), B-3
Program counter (PC), 4-1
Program stack, 1-2

.RAD50 directive, 5-12
Radix controls, temporary, 5-14
.RADIX directive, 3-11, 5-14
Radix-50, 5-13
character set, A-l
Reentrant code, 1-4
Register addressing, 1-4
Register deferred mode, 4-2
Register destination, B-9
Register increment, 1-6
Register mode, 4-2
Register names, 1-5
Register symbols, 3-7
Register term indicator, 3-1
Register usage, 1-2
Relative deferred mode, 4-5
Relative mode, 4-5
Repeat block:
.REPT,6-13
Rubout key, 7-2

Subconditional directives, 5-20
Subroutine return, B-9
Subroutines, 1-2
Subtraction, 3-5
Subtraction operator, 3-2
Symbolic addressing, 1-2
Symbols,
automatically created, 6-7
local, 3-8
user-defined, 3-5

Table of contents for assembly
listing, 5-6
Tabs, 2-3
Temporary radix controls, 5-14
Terminal register indicator, 3-2
Terminating directives, 5-17
Terminators, 3-1
Terms in expressions, 3-11, 3-12
.TITLE directive, 5-3
Trap handler, 1-5
Trap instructions, B-7
Truncation, 3-11, 4-7, 5-8, 5-9
2's complement, 3-4, 3-11

Unary operators, 3-4, 3-12, 5-15
Underbar ( ) usage, 7-1
Up arrow (t), 3-2, 3-3
User-defined symbols, 3-5
User Symbol Table, 3-5, 3-8

Vertical formatting, 2-4
Vertical tab, 2-1, 3-1

.WORD directive, 2-3, 5-9
.SBTTL directive, 5-5
Semicolon (;) usage, 2-3, 3-2
Single-operand instructions, B-4
Single quote ('), 3-2, 6-8
Slash (/), 3-2
Source file, 7-2
Source program format, 2-1
Spaces, 2-3, 3-1, 3-3
Special characters, B-1
Special characters within
arguments, 6-5
Statement format, 2-1
Statement terminator, 2-1, 3-1
Storage area, reserved, 3-11
Storage space, 1-5
Index-3

MACll XVM Assembler
Language Manual
DEC-XV-LMLAA-A-D
READER'S COMMENTS
NOTE:

This form is for document COIT~ents only.
Problems
with software should be reported on a Software
Problem Repcrt (SPR) form.

Did you find errors in this manual?

If so, specify by page.

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Please make suggestions for improvement.

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required for use of the software described in this manual? If not,
what material is missing and where should it be placed?

Please indicate the type of user/reader that you most nearly represent.
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[]

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[]

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[]

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[]

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