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DEC-D8-ASAA-D

December 1968

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PAL-D

DISK ASSEMBLER

DEC-D8-ASAA-D

PAL-D DISK

ASSEMBLER

Programmer’s Reference Manual
ApriI I968

For additional

copies order No. DEC-DB-ASAA-D from
Digital Equipment Corporation, Program Library, Maynard, Mass. Price $I .00

DIGITAL EQUIPMENT CORPORATION

MAYNARD. MASSACHUSETTS

CONTENTS

CHAPTER I
INTRODUCTION
PAL-D Language

Syntax

Legal Characters
Illegal Characters
Format Ettectors
Statements

Labels

Operators

'V'V‘eiaia'edeeeeeeewewww

Operands
Comments

Symbols
Symbol Distinction
Permanent Symbols
—l

ompw

User-Defined Symbols

Symbolic Address
Symbolic Operators

Symbolic Operands
Symbol Tables
Direct Assignment Statements

Numbers
Arithmetic and Logical

Operators

Evaluating Expressions
Address Assignments
Current Address Indicator
Indirect Addressing

Autoindexing
Literals

Nesting Literals
Instructions

Memory Reference Instructions
Paging

CONTENTS (Cont)
.7.I.2

Off—Page Referencing

.7.2

Augmented Instructions

.7.2.1

Operate Microinstructions

.7.2.2

Input-Output Transfer Microinstructions
CHAPTER 2

PSEUDO-OPERATORS

NMNNN owomtnom

Current Location Counter

2-]

Extended Memory

2-]

Radix Control

2-2

Listing Control

2-2

Text

2-2

Facility

End of Program

2-3

End of File

2-3

Altering the Symbol Table

2—3

CHAPTER 3
OPERATING PROCEDURE

0000

Loading PAL-D

3-1

Saving PAL-D

3-2

Expanding User's Symbol Table

3—2

Using PAL-D

3-2

CHAPTER 4
PROGRAM PREPARATION AND ASSEMBLER OUTPUT

#kA-b

Program Tape

4-1

Assembly

4-2

.2.I

Pass I

4-2

.2.2

Pass 2

4-2

.2.3

Pass 3

CHAPTER 5

ERROR DIAGNOSTICS
APPENDIX A

USA SCII CHARACTER SET
APPENDIX B
SYMBOL LIST

HOW TO OBTAIN REVISIONS AND CORRECTIONS

Notification of changes and revisions to currently available Digital software
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information appears in a section of DECUSCOPE called

"Digital Small Computer

News".

Revised software products and documents are shipped only after the Program

Library receives a specific request from a user.
DEC USCOPE is distributed periodically to both DECUS members and to non-

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CHAPTER I

INTRODUCTION

PAL-D, the acronym for _Program Assembly Language for the _Disk System, is the symbolic

assembly program designed primarily for the 4K PDP-8 family of computers with disk or DECtape.
The PAL-D Assembler makes machine

language programming easier, faster, and more

efficient.

Basically, the Assembler processes the programmer's source program statements by translating

mnemonic

operation codes to the binary codes needed in machine instructions, relating symbols to

numeric values,

assigning absolute core addresses for program instructions and data, and preparing an

output listing of the program, which includes notification of any errors detected during the assembly
process.

The PAL—D Assembler operates under the Disk Monitor

the disk version of the

System.

The assembly system includes

Symbolic Tape Editor for altering or editing the source language tape, the Disk

Debugging Tape for debugging the obiect program by communicating with it in the source language,
and various other utility programs.

PAL-D requires a 4K

TCOI

DECtape unit, or both.

PDP-8/I, 8, or 8/5 computer with a teleprinter, and a DF32 Disk or

It can also use a high speed reader and punch, and
up to three additional

D532 Disk units.

PAL—D LANGUAGE

l.1

The PAL-D Assembler is compatible with the PAL III Assembler.

However, PAL-D has the

following additional features.
Operators

Symbols and integers may be combined by
using the operators
+
-

Literals

Addition

8. Boolean AND

Subtraction

Boolean Inclusive OR

Symbolic or integer literals (constants)
automatically assigned.

are

Text Facility

Text facilities exist for single characters
and blocks of text.

Indirect

Linkage

Generation

Indirect links are automatically generated for

off-page referencing.

SYN TAX

Programs processed under PAL-D are written using USA SCII characters. Appendix A
contains a complete list of these characters with their octal code
equivalents.

I-I

1 .2.1

Legal Characters
The following characters are acceptable to PAL-D.

The alphabetic characters

ABCD.

.XYZ

The numeric characters
0123456789

The special characters

__.

Space

Separates symbols and numbers
(see Section 1.5.1)

Plus

Combines symbols or numbers

Minus

Combines symbols or numbers

Exclamation Mark

Combines symbols or numbers

Carriage Return

Terminates a line

(add)
-

(subtract)
(inclusive OR)
Formats symbols or numbers or source

Tabulation

tape output

Assigns symbolic address
Direct assignment of symbol values
Terminates coding line
(will not terminate comments)

Comma

Equal Sign
Semicolon
Dollar Sign

Indicates end of pass

Asterisk

Sets current location counter; redefines origin

Point

Has value equal to current location counter

(Period)

Slash

Indicates start of comment

Ampersand

Combines symbols or numbers

Quote

Generates USA SCll constant

(AND)

()

Parentheses

Defines literal on current page

Brackets

Defines page 0 literal

Ignored characters
Form-Feed

Indicates the end of a
source

Used for

Code 200

Used for leader/trailer

leader/trailer

Rubout

Follows tabulation characters for

Line-Feed

timing purposes
Follows carriage return and causes teleprinter paper to roll upward one line
(i.e., nonprinting), the following symbols are used

throughout this manual to represent their presence.
I—I

program

Blank Tape

Since certain characters are invisible

.4
J

logical page of

Space
Tabulation

Carriage Return

1.2.2

Illegal Characters
All characters other than those listed above are illegal when not in a comment or TEXT field

and, being illegal, their occurrence causes the error message IC (Illegal Character) to be printed by
PAL—D.

2 .3

Format Effectors

Tabulations are usually used in the body of a source program to provide a neat page; they can

separate fields from one another, as between a statement and a comment.

For example,

line written

GO, TAD TOTAL/MAIN LOOP
is much easier to read if tabs are inserted to form

GO, -'l TAD TOTAL—ti /MAIN LOOP
Either the ";"
statement terminator.

(semicolon) or ”J

(carriage return-line feed) character may be used as a

The. semicolon is considered identical to carriage return-line feed except that it

will not terminate a comment.

Example:

TAD A
The entire expression between the

TAD B J

/THIS IS A COMMENT;

"/" (slash) and J (carriage return) is considered a comment.

The semicolon also allows the programmer to place several lines of coding on a single line.

If, for example, he wishes to write a sequence of instructions to rotate the contents of the accumulator
and link six places to the right, it might look like

RTR 2

RTR I

RTRJ

The programmer may place all three RTRs on a single line by separating them with the special character
,

and terminating the line with a carriage return.

The above sequence of instructions can then be

written

RTR; RTR; RTRJ
This format is particularly useful when setting aside a section of data storage for a list.
IZ—word list could be reserved by

LIST,

A neat printout

For example,

specifying the following format.
0;

O J

(or program listing) makes subsequent editing, debugging, and interpretation

much easier than when the coding is laid out in a haphazard fashion.

1 .3

STATEMENTS
PAL—D source programs are usually prepared on a Teletype, with the aid of the Editor,

sequence of statements.

Each statement is written on a single line and is terminated by

return-line feed sequence.
are

not

as a

carriage

PAL-D statements are virtually format free; that is, elements of a statement

placed in numbered columns with rigidly controlled spacing between elements, as in punched-card

oriented assemblers.

There are four types of elements in a PAL-D statement which are identified by the order of
appearance in the statement, and by the separating,

delimiting, character which follows or precedes

the element.
Statements are written in the general form

label, operator operand/comment
The Assembler interprets and processes these statements, generating one or more binary instructions or
data words,

performing an assembly process. A statement must contain at least one of these elements

and may contain all four types.

1.3.1

Labels
A label is the symbolic

statement in the program.

l .3.2

name

created by the source programmer to identify the position of the

If present, the label is written first in a statement and terminated by a comma.

Operators
An operator may be one of the mnemonic machine instruction codes (see Appendix B),

pseudo-operation (pseudo-op) code which directs assembly processing.

codes are described in Chapter 2.
a

The assembly pseudo-op

Operators are terminated with a space if an operand follows or with

semicolon, slash, or carriage return.

1 .3.3

Operands
Operands are usually the symbolic address of the data to be accessed when an instruction is

executed, or the input data or arguments of a pseudo-op.
a

statement depends on the statement operator.

comment

1 .3.4

In each case,

interpretation of operands in

Operands are terminated by a semicolon, a slash if a

follows, or a carriage return-line feed.

Comments
The programmer may add notes to a statement following a slash mark.

affect assembly processing or program execution, but are useful in the program
or

debugging

1-4

Such comments do not

listing for later analysis

l .4

Symbols
The programmer may create symbols to use as statement

labels, as operators, and as operands.

A symbol is a string of one or more alphanumeric characters delimited by

punctuation character.

symbol contains from one to six characters from the set of 26 alphabetic characters and ten digits 0 through
9; however, the first character must be alphabetic.

Symbol Distinction

1.4.1

The PAL—D Assembler makes a distinction between the types of symbols it is processing. These

types are
a

Permanent symbols

symbol whose value of 4000 (octal) is taken from PAL-D's permanent
operation code symbol table.

JMS

User-defined symbols
HERE

user-defined symbol; when used as a symbolic address tag, its value is

the address of the statement it tags

l .4.1 .1

Permanent

Symbols

(this value is assigned by PAL—D).

PAL-D has in its permanent symbol table definitions of its operation codes,

operate commands, and many input—output transfer (IOT) microinstructions (see Appendix B).

PAL-D's

permanent symbols may be used without prior definition by the user.

1 4.1 .2

if any,

User-Defined Symbols

are

User-defined symbols are composed according to the following rules.

The characters must be

The first character

Only the first six characters of any symbol are meaningful to PAL-D; the remainder,

alphabetic (A—Z) or numeric (0-9).

must be alphabetic.

ignored.

Note that because of the third rule above,
since the seventh character is

symbol such as INTEGER would be interpreted as INTEGE

ignored. Remember,

if symbols of more than six characters are used, the

programmer must avoid defining two apparently different symbols whose first characters are identical.

For example, the two symbols GEORGEl and GEORGE2 differ only in the seventh character, thus the

Assembler treats them as being the same symbol, GEORGE.
When the symbol

field delimiter.

following the space is a user-defined symbol, the space acts as an address

Example:
A,

"2117;l
CLAJ

JMP,__,A 4/
1-5

where A is user-defined symbol with the value 21 l 7.

Address

JMP

lOl

000

000 (binary representation of permanent symbol

000

Oil

001

ill

The operation codes (op codes) are

written more concisely in octal

JMP)

(binary representation of address A)

inclusively ORed to form
JMPA

The expression JMP A is evaluated as follows.

101

001

Oil

ill

5317.

Symbolic Addresses

l .4.3

A symbol used as a label to specify a symbolic address must appear first in the statement and
must

be immediately Followed by

defined symbol

can

defined as a label

comma.

When used in this way,

symbol is said to be defined.

reference an instruction or data word at any point in the program.

only once.

second or successive attempt is
definition.

These are

A symbol

can

If a programmer attempts to define the same symbol as a label again, the

The Assembler recognizes only the first

ignored and an error is indicated.

legal symbolic addresses:
ADDR,
TOTAL,
SUM,

The following symbolic addresses are illegal:

7ABC,

LABH,

1 .4.4

(first character must be alphabetic)
(comma must immediately follow label)

Symbolic Operators
Symbols used as operators must be predefined by the Assembler or by the programmer.

statement

space,

has no label, the operator may appear first in the statement, and must be terminated by a

tab, semicolon, or carriage return.
TAD
PAGE
ZIP

1 .4.5

If a

The following are examples of legal operators:

(a mnemonic machine instruction operator)
(an Assembler pseudo-op)
(legal only ifdefined by the user)

Symbolic Operands
Symbols used as operands must have a value defined by the user.

These may be symbolic

references to previously defined labels where the arguments to be used by this instruction are to be found,
or

the values of symbolic operands may be constants or character strings.

TOTAL,
The first operand, ACl ,
ACT

by the user.

TAD ACl

TAG

specifies an accumulator register, determined by the value given to the symbol

The second operand references a memory location whose name or symbolic address is TAG.

1—6

Symbol Tables

1.4.6

The Assembler processes symbols in source program statements by referencing its symbol tables
which contain all defined symbols along with the binary value assigned to each symbol.

Initially, the Assembler's permanent symbol table contains the mnemonic op codes of the machine
instructions and the Assembler pseudo-op codes,

listed in Appendix B.

As the

source

program is

processed

symbols defined in the source program are added to the user's symbol table.

1 .4.o.1

Direct Assignment Statements

—

The programmer inserts new symbols with their assigned values

directly into the symbol table by using a direct assignment statement of the form

symbol
where the value may be

number or expression.

value

For example,

ALPHA=5
BETA=17
A direct assignment statement may also be used to give a new symbol the same value as a

previously defined symbol.
BETA=17

GAMMA=BETA
The new symbol,

GAMMA,

is entered into the user's symbol table with the value 17.

The value assigned to a symbol may be changed.

ALPHA=7

changes the value assigned to the first example from 5 to 7.
The user may also define symbols by use of the comma.

When the first symbol of a statement is

terminated by a comma, it is assigned a value equal to the current location counter

*100

TAG,

(CLC).

For example,

/set CLC (origin) to 100:)

CLAJ
JMP AJ

DCA B.)

The symbol TAG is assigned a value of 0100, the symbol B a value of 0102, and the
symbol A a value of

0103.
Direct assignment statements do not generate instructions or data in the obiect program.
statements are used to

1.5

These

assign values so that symbols can be conveniently used in other statements.

NUMBERS

Any sequence of numbers delimited by a punctuation character is interpreted numerically by
PAL-D

4372
The radix control
used in number
are

pseudo-operators (pseudo—ops) indicate to the Assembler the radix to be

interpretation (see Chapter 2).

The pseudo-op DECIMAL indicates that all numbers

interpreted as decimal until the next occurrence of the pseudo—op OCTAL.

The pseudo—op

OCTAL indicates that all numbers are to be interpreted as octal until the next occurrence of the pseudo-op
DECIMAL.
The radix is initially set to octal and remains octal unless otherwise specified.

1 .5.l

Arithmetic and Logical

Operators

The arithmetic and logical operators are:
+

Plus

25 complement addition

(modulo 4096)
-

25 complement subtraction

Minus

(modulo 4096)
I

Boolean inclusive OR

Exclamation Mark

(union)
&
_.

Boolean AND (intersection)

Ampersand

Interpreted as inclusive OR when used

Space

to separate two

symbolic operators. Example:

TAG,

l .5.2

CLA L_.CLL J

Evaluating Expressions

Symbols and numbers (exclusive of pseudo—op symbols) may be combined by using the arithmetic
and

logical operators to form expressions.

Expressions are evaluated from left to right.
'

Value

Value
Value

1.6

A+ B

A—B

AI B

A&B

0002

0003

0005

7777

0003

0002
0005
0000

0007

0005

0014

0002

0007

0700

0007

0707

0671

0707

Example:

ADDRESS ASSIGNMENTS
The PAL—D Assembler sets the origin,

starting address, of the source program to absolute

location (address) 0200 unless the origin is specified by the programmer.

As source statements are processed,

PAL-D assigns consecutive memory addresses to the instructions and data words of the object program
is done by

incrementing the location counter each time a memory location is assigned.

1-8

This

A statement which

generates a single object program storage word increments the location counter by one.
may generate six storage words, thus

Another statement

incrementing the location counter by six.

Direct assignment statements and some Assembler pseudo-ops do not generate storage words
and therefore do not affect the location counter.

Current Address Indicator

l .6.l

The special character
current

(point or period) always has a value equal to the value of the

It may be used as any integer or symbol

location counter.

(except to the left of an equal sign).

Example:
*200J
JMP .+ 21
is

equivalent to JMP 0202. Also,
*3001

.+24OOJ
will

produce in location 0300 the quantity 2700.

Consider

*22002
CALL=JMS |
0027:.)
The second

line, CALL

JMS I

does not increment the current location counter,

therefore, 0027 is

placed in location 2200 and CALL is placed in the user's symbol table with an associated value of 4600
(the octal equivalent of JMS 1.).

1.6.2

Indirect Addressing

When the character I appears in

statement between

memory reference instruction and an oper-

and, the operand becomes the address containing the address of the statement to be executed. Consider
TAD 400
which is a direct address statement, where 400 is interpreted as the address containing the quantity to be
added to the accumulator.

Thus, if address 400 contains 0432, then 0432 is added to the accumulator.

Now consider

TAD I 400
which is an indirect address statement, where 400 is

interpreted as the address of the address containing

the quantity to be added to the accumulator.

if address 400 contains 432, and address 432 contains

Thus,

456, then 456 is added to the accumulator.
When a reference is made to an address not on the same page as the reference, PAL-D sets
the indirect bit
reference

(bit 3) of the machine instruction, generating an indirect address linkage to the off-page

(see Paging and Off-Page Referencing,

Sections l .7.1 .l and 1.7.1 .2).

1—9

In the case of several

off-page references to the same address, the indirect address linkage

will be generated only once.

Example:
A,

*ZII7J
CLAJ

*26OOJ
TAD_.A

DC.A__.A
The space preceding the user-defined symbol A acts as an address field delimiter.

PAL-D will

recognize

that the address tag A is not on the current page (in this case 2600-2777) and will generate a link to it
in the following manner.

In location 2600, PAL-D will

place the word
(octal equivalent of TAD I 2777)

I777

and in location 2777 (the last location on the current page) the word 2II7 (the actual address of A) will

be placed.
a

When it sees the second reference to A it will

use

the previous link word rather than creating

new one .

PAL—D will

recognize and generate an indirect address linkage only when the address referenced

is to a location on another page, not the current page.

The programmer must use the character I to

indicate an explicit indirect address when indirectly addressing to a location on the current page.
PAL-D cannot generate a link for an instruction that is already specified as being an indirect

address.

In this case, PAL-D will

type the error message ll (Illegal Indirect); the error message is ignored

and assembly is continued.

I .6.3

Autoindexing

Interpage references are often necessary for obtaining operands when processing large amounts
of data.

The PDP—8 computers have facilities to ease the addressing of this data.

I0 to I7 (octal) are
an

When absolute locations

indirectly addressed, the content of the location is incremented before it is used as

address and the incremented number is left in the location.

This allows the programmer to address

consecutive memory locations using a minimum of statements.
It must be remembered that initially these locations (I0 to I7) must be set to one less than the

first desired address.

Because of their characteristics, these locations are called autoindex registers.

No incrementation takes place when locations I0 to I7 are addressed directly.

Example:
Statement is in location 500
Data is on the page starting at 5000

Autoindexing register I0 is used for addressing

1377

0477

3010

DCA 10

0500

1410

TAD I 10

’

0577

/ set up auto
/ index with 4777
/ C(10) is incremented to 5000 before

(5000-1)

TAD

0476

4777

use as

address

literal

generated by PAL-D

When the statement in location 500 is executed, the content of location 10 will be incremented to 5000
and the content of location 5000 will be added to the content of the accumulator.

If the instruction

TAD | 10 is re—executed, the content of location 5001 is added to the content of the accumulator, and so on.

1.6.4

Literals

Symbolic and integer literals (constants) may be defined as shown below.

cDAJ
TAD

(2).;

DCA INDEX .2

The left parenthesis is a signal to the Assembler that the
in the table at the top of the current page.
are

stored.

This is the same table in which the indirect address linkages

In the above example, the quantity 2 is stored in the first free location in a list beginning at

the top of the current page
an

integer following is to be assigned a location

(relative address 177), and the statement in which it appears is encoded with

address referring to that location.

A literal is assigned to storage the first time it is encountered; subsequent references will be
to

the same location.
If the programmer wishes to assign literals to page 0 rather than the current page, he must use

square brackets,
or

[ ],

in place of parentheses.

Whether using parentheses or square brackets, the right

closing member is optional and may always be replaced with a carriage return.
TAD

1.6.4.1

Nesting

(777.;

Literals may be nested as shown below.
*200 2

TAD (TAD

(30 a

will generate
0200

1276

0376

1377

(literals assigned to locations

0377

0030

0377 and 0376; top of current page)

This type of nesting may be carried to many levels.

Literals are stored on each page
may be placed on page 0)

starting at relative address

I77 (only

If literals are being generated for some nonzero

is set to another page, the current
page literal buffer is punched out during
to the

I2710

I778 literals

page and then the origin
pass 2.

If the origin is reset

previously used page, the same literal will be generated if used again.
If a single character is

preceded by a quote (”)

character is inserted instead of taking the letter as a

Example:

the 8-bit value of the USA SCII code for that

symbol.

CLAo/
TAD ("A I

will place the constant 0301 in the accumulator.

I.7

INSTRUCTIONS
There are two basic groups of instructions:

reference instructions require an operand;

I .7.l

memory reference and augmented.

Memory

augmented instructions do not require an operand.

Memory Reference Instructions
In PDP-8 computers,

some

instructions require a reference to

They are appropriately

memory.

designated memory reference instructions, and take the following format.

OPERATION
CODES 0-5

MEMORY
PAGE

fifi

W4
INDIRECT
ADDRESSING

ADDRESS

Memory Reference Instruction Bit Assignments
Bits 0 through 2 contain the operation code of the instruction to be
performed
or

JMP)

Bit 3 tells the computer if the instruction is
indirect, that

(AND, TAD, DCA, JMS, or

is, if the address of the instruction

specifies the location of the operand, or if it specifies the location of the address of the operand.
tells the computer if the instruction is

through

referencing the current page or page zero.

( 7 bits) to specify an address.

In these 7 bits, 200 octal

This leaves bits 5

I28 decimal locations may be

specified; the page bit increases accessible locations to 400 octal or 256 decimal.
The address field of a memory reference instruction

Example:

A=27O J
*200 c'
TAD

I-I2

A-20 J

Bit 4

may be any valid expression.

produces, in location 200, the word
1250
001

which in binary is

010

000

101

which is also TAD 250.

1 .7.1 .1

Mtg

To ease the programmer's addressing problems,

divides memory into sectors called pages.
0 to 177 (octal) on that page.

convention has been defined that

Each page contain 200 octal locations (128 decimal) numbered

There are 40 octal

32 decimal pages numbered 0 to 37 (octal)

examples of page numbers and the absolute and relative locations (addresses)

are

shown below.

Some

It must

however, that there is no physical separation of pages in memory.

be borne in mind,

Absolute

Relative

Eggs

Address

200

400

7400

7600

—

177

377

577

7577

7777

177

—

177
177

The Following table offers a comparison of specific absolute and relative addresses on the
same

page

Absolute
Address

Relative
Address

617

2577

177

6255

7777

177

133%

Since only seven bits are necessary to address 200 octal

for this function

1 .7.1 .2

locations, bits 5 to 11 are reserved

Off-Page Referencing

from bit 4 of the instruction.

The page on which an absolute address is contained can be determined

If bit 4 is a 0, the address refers to a location on page 0; if bit 4 is a 1,

the address refers to a location on the current

(same) page, that is, the some memory page as the instruction.

Augmented Instructions

1 .7.2

Augmented instructions are divided into two groups:

Operate and input-output transfer

microinstructions.

1.7.2.1

Group
are

Operate Microninstructions

—

Within the operate group there are two

1 microinstructions are
principally for clear,

complement, rotate, and increment operations and

designated by the presence of a O in bit 3 of the machine instruction word.

CLA

CMA

ROTATE
AC ANDL
RIGHT

F—H

,__~_fi

r___A._fi

OPERATION
CODE 7
A

‘

groups of microinstructions.

(See Appendix B.)

ROTATE 1
POSITION IF AO,
ZPOSITIONS
IFAt

f—A—fi

C_Y__J

W—J

\_.Y__J

O_Y__J

CONTAINS

CLL

CML

ROTATE
AC AND L

IAC

TO
SPECIFY
GROUPt

LEFT

Group 1 Operate Microinstruction Bit Assignments

Group 2 microinstructions are used principally in checking the content of the accumulator and
link and, based on the check, continuing to or skipping the next statement.

Group 2 microinstructions are

identified by the presence of a 1 in bit 3 and a O in bit 11 of the machine instruction word (See
Appendix B).

REVERSE
SKIP
SENSING OF

OPERATION
CODE

CLA

BITS

SZA
r—J_\

f——“—'\

HLT

5,6,7

/—~—\

/——~—\

\—v--’

L_Y__J

CONTAINS A1
TO SPECIFY
GROUP 2

SMA

SNL

OSR

CONTAINS AO
TO

SPEC‘EY

GROUPZ

Group 2 Operate Microinstruction Bit Assignments

Group 1 and group 2 microinstructions can not be combined because bit 3 determines only one
or

the other.
Within Group 2, there are two groups of skip instructions.

OR group and the AND group.

They may be referred to as the

AND Group

OR Group

SMA

SPA

SZA

SNA

SNL

SZL

The OR group is designated by a O in bit 8, the AND group by a l in bit 8.

OR and AND group

instructions cannot be combined because bit 8 determines only one or the other.

If the programmer does combine

under which

legal skip instructions, it is important to note the conditions

skip may occur.
QR Group

—

If these skips are combined in a statement, the inclusive OR of the conditions

determines the skip.

SZA

SNL

The next statement is skipped if
the accumulator contains 0000,
the link is a

l, or

both conditions exist.
b.
determines the

AND Group

skip

If the skips are combined in a statement, the

logical AND of the conditions

SNA

SZL

The next statement is skipped only if the accumulator differs from 0000 and the link is O.

1 .7.2.2

Input-Output Transfer Microinstructions

These microinstructions initiate operation of

peripheral equipment and effect information transfer between the central processor and the input-output
device
B

(5).

This is the principal function of the input-output transfer (IOT) microinstructions.

lists all valid IOT microinstructions, and each is discussed in detail in the User's Handbook.

Appendix

CHAPTER 2

PSEUDO-OPERATORS

The programmer may use pseudo-operators (pseudo-ops) to direct the Assembler to perform
certain tasks or to interpret subsequent coding in a certain manner.

Some pseudo-ops generate storage

words in the object program, other pseudo—ops direct the Assembler on how to proceed with the assembly.

Pseudo-ops are maintained in the Assembler's permanent symbol table.
The function of each PAL-D pseudo-op is described below.

2.]

CURRENT LOCATION COUNTER
The programmer may

use

the PAGE pseudo-op to reset the current location counter

(CLC) to

the first location on a specified page.

PAGE

without an argument, the CLC is reset to the first location on the
next succeeding page.

Thus, if a program is being assembled into

page I and the programmer wishes to begin the next segment of his
program on page 2, he need only insert

JMP

.—71

PAGE, as follows.

(Last location used on page I)

PAGE I

CLAJ
PAGE n

resets
a

the CLC to the first location of page n, where n is an integer,

previously defined symbol, or a symbolic expression. Example:
PAGE 2
PAGE 6

2.2

(First location on page 2)

(sets the CLC to location 400)
(sets the CLC to location I400)

EXTENDED MEMORY

When using more than one memory bank, the pseudo-op FIELD instructs the Assembler to output
a

field setting.
FIELD n

where n is an integer,
defined symbol,

or a

previously

symbolic

expression within the range 0 S n 57.
This pseudo-op causes a field setting (binary word) of the form
II XXX 000
to

be output on the binary tape during pass 2.

where 000 _<_XXX _<_ I II
This word is interpreted by the

loading information from the Loader into the new field.
2—I

Loader, which then begins

RADIX CONTROL

2.3

Integers used in a source program are usually taken as octal numbers. If, however, the
programmer wishes to have certain numbers treated as decimal, he may use the pseudo-op DECIMAL.

all integers in subsequent coding are taken as decimal until

DECIMAL

the occurrence of the pseudo-op OCTAL.

OCTAL

resets

the radix to its original octal base.

LISTING CONTROL

2.4

During pass 3, a listing of the source program is printed (punched).

The programmer may,

however, control the output of his pass 3 listing by use of the pseudo-op XLIST.
Those portions of the source program enclosed by XLIST will

XLIST

not appear in

the pass 3 listing.

TEXT FACILITY

2.5

The pseudo-op TEXT enables the user to represent a character or string of characters in USA SCII
code trimmed to six bits and packed two characters to a word.
are

The numerical values generated by TEXT

left-iustified in the storage words they occupy, with the unused bits of the last word filled with 05.
A string of text may be entered by giving the pseudo-op TEXT followed by a space,

delimiting

character, a string of text, and the same delimiting character.

Example:
TEXT“ ASTRING OF TEXTA
The first

printing character following TEXT is taken as the delimiting character, and the text string is

the characters which follow until the delimiting character is again encountered.
If the example above were at location 0200, the pass 3
200

2324

201

221 1

202

1607

203

4017

204

0640

205

2405

206

3024

207

0000

listing would be as follows.

/ST
/RI
/NG
/.__, 0
/F
/TE
/XT
/zero filled
.__.

NOTE

With TEXT, any printing character
may be used as a delimiting character.
2-2

END OF PROGRAM

2.6

The special symbol

$ (dollar sign) indicates the end of a program. When the Assembler

encounters

the $, it terminates the pass.

2.7

END OF FILE
The pseudo-op PAUSE signals the Assembler to stop processing the current

current pass is not

input file.

The

terminated, and processing continues when the user types TP on the Teletype.

When processing a segmented program, the programmer must use the PAUSE pseudo-op as
the last statement of each segment to halt processing,

giving him time to call (or insert, if paper tape

is being used) the succeeding segment of his program.

2.8

ALTERING THE SYMBOL TABLE
There are two pseudo-ops that may be used to alter the permanent symbol table during pass l.

EXPUNGE

Erases the entire symbol table, except for pseudo-ops.

FIXTAB

FIX the symbol TABle.
are

All symbols currently in the symbol table

made permanent.

Example:
EXPUNGE J
TAD

TOOOJ

FlXTABJ
will

place the symbol TAD in the permanent symbol table.

symbols are not typed out with the users symbols on PASS 2.

All other symbols will be erased.

Permanent

CHAPTER 3
LOADING AND OPERATING PROCEDURES

The user receives the PAL-D Disk Assembler in binary format on 8-channel

tape.

punched paper

The Assembler is incorporated in the system by loading the paper tape into core using the Disk

Monitor System (Monitor).

Then the Assembler may be saved on the disk or DECtape as explained below.

If the Monitor is not present on your disk or DECtape, build it according to instructions in
the Disk Monitor System (DEC-D8-SDAA-D).

LOADING PAL-D

3.]

PAL-D is loaded in two passes.
are

The procedure for the two-pass load follows

(Loader responses

underlined).

_._LOAD1

call Loader from disk (2 indicates carriage return)

*IN-R: ,)

input to be from high speed reader; T: would indicate input from

Teletype reader
i:

Loader found device R: valid

two-pass load is specified

*OPT-Z 2

control is to be returned to the Monitor after loading tape into

.51.: J

core; 7600 I

would also transfer control to the Monitor after

loading the tape

Loader is waiting for user to put paper tape in reader and type TP.

After reading tape into core, Loader waits for user to remove tape
If checksum error occurs, Monitor types ? in place

and type TP.
of l.

Loader is waiting for user to put paper tape in reader for second pass
and type lP.

After reading tape on second pass, Loader is waiting for user to remove

l<l

P>l<l

P>l<lP>_l_<l

tape and type TP.

Again, checksum error will cause ? to be typed

in place of 1.

NOTE
lP indicates CTRL-P, and< >indicates that

the enclosed portion is not echoed

when the user types).

3-]

(printed

3.2

SAVING PAD-D

PAL—D may be saved on the system device as a system program.

This is done by typing the

following:

0—,3377 3600- 4377, 4600, 5200, 6200- 6577,

.SAVE PALD!
V

Progam

‘J

7000—

6200
7577;
JV

One Page

Entry

Save

Point

Name

Multiple Page
Save

System Program
Program

User

The PAL-D Assembler in now saved as a system program on the system device.

The programmer may now

type PALDJ which brings the Assembler into core for use with symbolic source programs.

3.2.l

Expanding User's Symbol Table
The user's symbol table can hold

T6010 user-defined symbols. This may

be expanded by

saving on the system device a user file named .SYM which can be used by PAL-D to store extra symbols.
The symbol table can be

Each user—defined symbol occupies four words.

locations by saving a file with the following statement.
L

3.3

SAVE

expanded by 12810

2008

.SYM:0-l77;0 1

USING PAL-D
PAL-D is transferred from the system device into core using the Monitor.

The user begins by

typing

_._PALD J
PAL-D requests on output file by typing

*OUTThe user selects the output device by typing

(low speed reader/punch), or

T: J

for the Teletype

R: J

for the high speed reader/punch,

Szname J

for output to the system device as file name:

PAL-D now types
*IN-

3-2

and waits for the user to select the

input files. Up to five input files may be specified (e.g., R:, R:,

S:name, R:, R: J ),but in this example the user selected

input from the high speed reader/punch

R:.)

NOTE
PAL—D checks the validity of each selected file

(i.e.,

valid only if the file was declared when building Moni-

tor), and types
valid file.

for each valid file and ? for an in-

When PAL-D finds an invalid file it returns

control to the Monitor, in which case, the user must
start again

by calling PALD J

When PAL-D is satisfied that the input file(s) is valid,

it will

request third pass listing option by typing

*OPT—

The user may type
T .1

meaning listing and symbols are to be produced
on

R J

the Teletype,

meaning listing and symbols are desired on high
speed punch, or
meaning symbols only same as (any other character means
no

When the high speed punch is selected as a

third pass)

listing device, the alphabetic symbol table produced at the

end of pass 2 is also produced on the high speed punch.

PAL-D will

now

proceed with the assembly, pausing only when user intervention is required

(i.e., placing a new paper tape in the reader, turning on the punch, etc.)
PAL-D will type an up-arrow
user

On these occasions,

(T ) on the Teletype to indicate user intervention is required.

is ready to continue with the assembly, he types CTRL-P

When the

( T P) (which does not echo).

At the end of pass 2, PAL-D outputs the user's symbol table in alphabetical order (in addition
to

the assembled binary output).

This symbol table listing may be terminated at any time by typing

CTRL—P, and PAL—D will proceed to initiate pass 3, if requested.

Assembly may be terminated and control returned to the Monitor at any time by typing
CTRL-C (TC)

When the assembly is complete, control will

automatically be returned to the Monitor.

CHAPTER 4

PROGRAM PREPARATION AND ASSEMBLER OUTPUT

The source

language tape (symbolic tape) is prepared in USA SCH code on 8-channel punched

paper tape or as a named file on the disk or

4.1

DECtape using the Editor.

PROGRAM TAPE
Since the Assembler ignores certain characters, these may be used Freely to produce a more

readable

symbolic source tape.

These useful characters are tab and form-feed.

The Assembler will also

ignore extraneous spaces, carriage return-line feed combinations,

rubouts, and blank tape.
The program body consists of statements and pseudo-ops.

dollar sign ($).

The program is terminated by the

If the program is large, it may be segmented by use of the pseudo—op PAUSE.

This often

facilitates editing the source program since each section is physically smaller.

The Assembler initially sets the origin (current location counter) of the source program to 0200.
The programmer may reset the current location counter by use of the asterisk.
The following two programs are identical except that format effectors were used in the second

printout.
*200

/EXAMPLE OF FORMAT
/GENERATOR
BEGIN, o/START OF PROGRAM
KCC

KSF/WAIT FOR FLAG
.-T/FLAG NOT SET YET
KRB/READ IN CHARACTER

JMP

DCA CHAR
TAD CHAR
TAD MSPACE/IS IT A SPACE?

SNA CLA

HLT/YES
JMP BEGIN + 2/NO:

INPUT AGAIN

CHAR, O/TEMPORARY STORAGE
MSPACE, -240/—ASCII EQUIVALENT

/END OF EXAMPLE
$
*200

/EXAMPLE OF FORMAT
/GENERATOR
BEGIN,

/START OF PROGRAM

KCC
KSF

JMP

.-T

/WAIT FOR FLAG
/FLAG NOT SET YET
4-1

/READ IN CHARACTER

KRB

DCA CHAR

TAD CHAR

/IS IT A SPACE?

TAD MSPACE

SNA CLA

/YES
/NO: INPUT AGAIN
/TEMPORARY STORAGE
/—ASCII EQUIVALENT

HLT
JMP BEGIN+ 2

CHAR,
MSPACE,

-24o

/END OF EXAMPLE
$
Both of these programs will

produce the same binary code.

The second,

however,

is easier to read.

ASSEMBLY

4.2

PAL-D is a two-pass assembler with an optional third pass which produces a side-by-side

assembly listing of the symbolic source statements, their octal equivalents, and assigned absolute
addresses

4.2.1

Passl

During pass 1,

PAL—D processes the source tape

the definitions of all symbols used.

(or file) and places in its user's symbol table

The user's symbol table is printed (or punched) at the end of pass 2.

If any symbols remain undefined at the end of pass 1, the US (Undefined Symbol) diagnostic is printed

during pass 2 when the undefined symbol is encountered (see Error Diagnostics).

The symbol table is

printed (or punched) in alphabetical order on either the teleprinter or high-speed punch.

The punched

symbol table may be used to expand DDT-8s symbol table for use in program debugging.

If the program

listed above were assembled, PAL-D would output the following symbol table.

4.2.2

BEGIN

0200

C HAR

0213

MSPACE

0214

Pass2

During pass 2, PAL-D processes the source tape (or file) and generates binary output using the

symbol table equivalences defined during pass I

The binary output may be loaded in core by the Disk

Monitor System Binary Loader.
The binary coded tape (or file) consists of leader code,

origin setting, and data words.

Every occurrence in the source program of an asterisk causes a new origin setting in the binary output.
At the end of the binary coded tape,

binary checksum is produced and trailer code is generated.

4-2

When using the low speed paper tape punch,
and will be preceded and followed by rubouts.

rubouts

diagnostic messages are both typed and punched

The Binary Loader will ignore everything enclosed within

4.2.3

Pass 3

During pass 3, PAL—D processes the source tape (or tile) and prints out a side—by—side listing
of the generated octal code and the original source

the pass 3

language.

It the program shown above were assembled,

listing would be
*200

/EXAMPLE OF FORMAT
/GENERATOR

/START OF PROGRAM

0200

0000

0201

6032

KCC

0202

6031

KSF

0203

5202

JMP

0204

6036

KRB

0205

3213

DCA CHAR

0206

1213

TAD CHAR

0207

1214

TAD MSPACE

0210

7650

SNA CLA

0211

7402

HLT

0212

5202

JMP BEGIN+2 /NO:

0213

0000

0214

7540

BEGIN,

CHAR,
MSPACE,

-240

/END OF EXAMPLE

.—1

/WAIT FOR FLAG
/FLAG NOT SET YET
/READ IN CHARACTER

/IS IT A SPACE?

/YES
INPUT AGAIN

/TEMPORARY STORAGE
/-ASCII EQUIVALENT

CHAPTER 5
ERROR DIAGNOSTICS

PAL-D makes many error checks as it processes source

detected, the Assembler prints an error message.

language statements.

When an error is

The Format oF the error messages is

ADDRESS

ERROR CODE

where ERROR CODE is a two-letter code which specifies the type oF error, and ADDRESS is either the

absolute octal address where the error occurred or the address oF the error relative to the last symbolic

tag (iF there was one) on the current page.
The programmer should examine each error indication to determine whether correction is

required.
PAL-D's error messages are listed and explained below.
Error

Code
BE

Explanation
Two PAL-D internal tables have overlapped
can

This situation

usually be corrected by decreasing the level oF literal

nesting or number oF current page literals used prior to this

point on the page.
DE

Systems device error

An error was detected when trying to

read or write the system device; aFter three

Failures, control is re-

turned to the Monitor.
DF

Systems device Full

The capacity oF the systems device has been

exceeded; assembly is terminated and control is returned to the Monitor.
IC

Illegal character
a comment

nor a

illegal character was processed neither in

TEXT Field; the character is ignored and the

assembly continued.
ID

Illegal redeFinition ot a symbol

—

An attempt was made to give a

previously deFined symbol a new value by other means than the
equal sign; the symbol was not redeFined.
IE

Illegal equals

An equal sign was used in the wrong context.

—

Examples:
TAD A

+= B

(the expression to the leFt oF the equal sign is not
single symbol or, the expression to the right oF
the equal sign was not previously defined)

A +B=C
11

Illegal indirect
not

-—

An oFF-page reFerence was made; a link could

be generated because the indirect bit was

5-]

already set.

Error

Code

Explanation

Example:
*200

TAD I A 1

PAGE J
7240 J

A,
PE

Current nonzero page exceeded

An attempt

override a literal with an instruction,

override an instruction with a

corrected

was

made to

literal; this can be

(l)

decreasing the number of literals on the page or

(2)

decreasing the number of instructions on the page.

Phase error

PAL-D has received input files in an incorrect order;

assembly is terminated and control is returned to the Monitor.
SE

Symbol table exceeded

—

Assembly is terminated and control is

returned to the Monitor; the symbol table may be expanded to
contain up to 1184 user symbols
on

by saving a file named .SYM

the system device.

Undefined symbol

A symbol has been

processed during pass 2

that was not defined before the end of pass 1

Page 0 exceeded

Same as PE except with reference to page 0.

APPEN DIX A

USA SCII CHARACTER SET

Character

Code

301

260

302

261

303

262

304
305
306

N<X§<CHmWQT02§FKLHIQWUOW>

Character

307
310

31 1

312
313

314

\OCDNO‘UW-kwM-‘O

263

264
265

Character

241

0m%:“'

90»

270
271

geVA"
+

244

245
246
250

251
252
253

254

315
316

242
243

247

266
267

Code

255
.

256

31 7

257

320

272

321

273

322

275

326

LAP-1.0”"

327

TAB

21 1

330
331

LINE FEED

21 2

CARRIAGE-RETURN

21 5

332

SPACE

240

RUBOUT

377

323
324

325

BELL

277

333
335
207

,APPEN DIX B

SYMBOL LIST

Mnemonic

Code

Operation

Event Time

MEMORY REFERENCE INSTRUCTIONS

AND

0000

TAD

1000

ISZ

2000

DCA

3000

JMS

4000

JMP

5000

logical AND
complement add
increment & skip it zero
deposit & clear AC
jump to subroutine
jump

GROUP 1 OPERATE MICROINSTRUCTIONS
NOP

7000

IAC

7001

increment AC

RAL

7004

rotate

AC & link left one

RTL

7006

rotate

AC & link left two

RAR

7010

rotate

AC & link right one

RTR

7012

rotate

AC & link right two

CML

7020

CMA

7040

complement link
complement AC

CLL

7100

clear link

CLA

7200

clear AC

operation

GROUP 2 OPERATE MICROINSTRUCTIONS

halts the computer

HLT

7402

OSR

7404

inclusive OR switch register with AC

SKP

7410

skip unconditionally
skip on nonzero link
skip on zero link
skip on zero AC
skip on nonzero AC
skip on minus AC
skip on plus AC (zero is positive)

SNL

7420

S-ZL

7430

SZA

7440

SNA

7450

SMA

7500

SPA

7510

COMBINED OPERATE MICROINSTRUCTIONS
CIA

7041

complement & increment AC

STL

7120

set

GLK

7204

STA

7240

LAS

7604

get link (put link in AC, bit 11)
set AC
-1
load AC with switch register

link to 1
=

PSEUDO-OPERATORS
DECIMAL
EXPUNGE
FIELD
FIXTAB
I

OCTAL
PAGE

B-1

—L—k—l—A—d

PSEUDO—OPERATORS
PAUSE
TEXT
XLIST
Z

Code

Mnemonic

Event Time

Operation
IOT MICROINSTRUCTION 5

Program Interrupt
ION

6001

turn

IOF

6002

turn

KSF

6031

KCC

6032

1
skip if keyboard/reader flag
clear AC & keyboard/reader flag

KRS

6034

read keyboard/reader buffer

KRB

6036

clear AC & read keyboard buffer, & clear

interrupt on
interrupt off

Keyboard/Reader
=

keyboard flag

Teleprinter/Punch
TSF

6041

TCF

6042

TPC

6044

TLS

6046

skip if teleprinter/punch flag
clear teleprinter/punch flag
load teleprinter/punch buffer,

select & print
load teleprinter/punch buffer,
select & print, and clear teleprinter/punch

flag
High-Speed Reader (Type PC02)
1

RSF

6011

skip if reader flag

RRB

6012

read reader buffer & clear flag

RFC

6014

clear flag & buffer & fetch character

High-Speed Punch (Type PC03)
PSF

6021

PCF

6022

PPC

6024

PLS

6026

Disk File and Control

(type DF32)

DCMA

6601

DMAR

6603

1
skip if punch flag
clear flag & buffer
load buffer & punch character
clear flag & buffer, load & punch
=

clear disk memory request & interrupt flags

load disk from AC, clear AC, read into core,
clear interrupt flag

DMAW

load disk from AC, write onto disk from core,

6605

clear interrupt flag
DCEA

6611

clear disk extended address & memory address
extension register

‘

DSAC

6612

skip if address confirmed flag

DEAL

6615

clear disk extended address & memory address

DEAC

6616

extension register & load same from AC

clear AC, load AC from disk extended address
1
register, skip if address confirmed flag
or
data
if
late,
error,
request
skip
parity
0 (no error)
write lock switch flag
=

DFSE

6621

B-2

Mnemonic

Code

DFSC

6622

DMAC

6626

Event Time

Operation

sl<ip if completion flag
completed)

(date transfer

clear AC, load AC from disk memory
address register

DECtape Transport

(Type TU55) and Control (Type TCOT)

DTRA

676T

read status register A

DTCA

6762

clear status register A

DTXA

6764

load status register A

DTSF

677T

skip on flags

DTRB

6772

read status register B

DTLB

6774

load status register B

Memory Extension Control (Type 183)
CDF

62nl

CIF

62n2

change to data field n
change to instruction field n

RDF

6214

read data field into AC 6-8

RIF

6224

read instruction field into AC 6-8

RMF

6244

restore memory

RIB

6234

read

field

interrupt buffer

B—3

(ADM—‘wM—‘

.........................................................................................

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PAL-D DISK ASSEMBLER

PROGRAMMER'S REFERENCE MANUAL
DEC-DB-ASAA-D

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Did you find this manual easy to use?

What is the most serious fault in this manual?

What single feature did you like best in this manual?

Did you find errors in this manual? Please describe.

Please describe" your position.
Name

Organization

Street

State

DIGITAL EOUIPMENT CORPORATION
PRINTED IN

MAYNARD. MASSACHUSETTS

U.S.A.