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AA-D343A-TC

July 1978

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Document:	TRAX ODT Reference Manual
Order Number:	AA-D343A-TC
Revision:	0
Pages:	76
Original Filename:	http://bitsavers.org/pdf/dec/pdp11/trax/AA-D343A-TC_TRAX_V1.0_ODT_Reference_Manual_Jul78.pdf

OCR Text

July 1978
This manual describes the use of the Online Debugging Tool on
TRAX sy~tems.

TRAX
ODT Reference Manual
Order No. AA-D343A-TC

OPERATING SYSTEMS AND VERSIONS:

TRAX Version 1.0

SOFTWARE VERSION:

3.1

To order additional copies of this document, contact the Software Distribution
Center, Digital Equipment Corporation, Maynard, Massachusetts 01754

digital equipment corporation · maynard, massachusetts

First Printing, July 1978

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 only be used or copied in accordance with the terms of such
license.
No responsibility is assumed for the use or reliability of software on
equipment that is not supplied by DIGITAL or its affiliated companies.

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
ASSIST-II

DECsystem-IO
DECtape
DIBOL
EDUSYSTEM
FLIP CHIP
FOCAL
INDAC
LAB-8
DECSYSTEM-20
RTS-8

MASSBUS
OMNIBUS
OS/8
PHA
RSTS
RSX
TYPESET-8
TYPESET-II
TMS-ll
ITPS-IO

CONTENTS

Page

PREFACE
0.1
0.2
0.3

MANUAL OBJECTIVES AND READER ASSUMPTIONS
STRUCTURE OF THE DOCUMENT
ASSOCIATED DOCUMENTS

v
v
vi

INTRODUCTION

1-1

1.1
1.2
1.2.1
1.2.2
1.2.3
1.3
1.3.1
1.3.2

ODT INTERNAL ORGANIZATION
OPERATIONAL DESCRIPTION
Linking ODT into the User Program
User Task Breakpoints
Relocation Registers
EXPRESSING ODT COMMANDS AND FUNCTIONS
Forms of Address Expressions
Examples of Address Expressions

1-2
1-2
1-3
1-3
1-4
1-5
1-6

CHAPTER

ODT CHARACTERS AND SYMBOLS

2-1

CHAPTER

ODT COMMAND SEQUENCES AND FUNCTIONS

3-1

3.1
3.2

PRINTING TASK ADDRESSES
COMMANDS FOR OPENING, CHANGING, AND CLOSING
LOCATIONS
Close Current Location:
<CR> or k<CR>
Open Next Sequential Location:
<LF> or
k<LF>
Open Word Location: / or a/
Open Byte Location: \ or a\
Open Preceding Location:
~ or k
Open PC-Relative Location:
or k
Open Absolute Location:
@ or k@
Open Relative Branch Offset Location:
> or k>
Return to Interrupted Sequence:
< or k<
ACCESSING USER PROGRAM GENERAL REGISTERS: $n
ACCESSING SPECIAL ODT INTERNAL REGISTERS:
$x or $nx
TASK BREAKPOINT COMMANDS:
aiB, ainB, B,
or nB
PROGRAM EXECUTION COMMANDS: G or aG
and P or kP
SINGLE-INSTRUCTION MODE COMMANDS: S or nS
SEARCH OPERATIONS
Word/Byte Search Commands: W, kW, miW,
or mikW
Not This Word/Byte Search Commands: N,
kN, miN, or mikN
Effective Address Search Commands: E, kE,
miE, or mikE
FILL COMMANDS:
F or kF

3-1

CHAPTER

3.2.1
3.2.2
3.2.3
3.2.4
3.2.5
3.2.6
3.2.7
3.2.8
3.2.9
3.3
3.4
3.5
3.6
3.7
3.8
3.8.1
3.8.2

3.8.3
3.9

iii

1-1

3-2
3-2
3-2
3-2
3-4
3-5
3-5
3-6
3-7
3-8
3-9
3-9
3-15
3-17
3-19
3-20
3-20
3-22
3-22
3-24

Page

3.15
3.16
3.16.1
3.16.2
3.16.3
3.16.4

OFFSET CALCULATION COMMANDS: aO or aikO
RELOCATION REGISTER COMMANDS:
ainR, aiR,
nR, or R
RELOCATION CALCULATOR COMMANDS:
ainK, nK,
or K
LISTING COMMANDS: L, kL, aiL, aikL, or
niaikL
REPRINTING OPEN LOCATIONS
Print Octal Byte Value: \
Print Byte Mode ASCII Characters:
or a l
Print Word Mode ASCII Characters:
"or a"
Print Word Mode Radix-50 Characters:
% or a%
INTERPRETING EXPRESSION VALUES: k=
USING SPECIAL ARGUMENTS IN ODT COMMANDS
Current Location Indicator: .
Constant Register Indicator: C
Quantity Register Indicator: Q
Radix-50 Operator: *

ERROR DETECTION

4-1

4.1
4.2

COMMAND INPUT ERRORS
TASK IMAGE ERROR CODES

4-1
4-2

PROCESSOR STATUS WORD

A-1

MODES

(MEMORY MANAGEMENT OPTION)
PRIORITY
TRAP (T-BIT)
CONDITION CODES
TRAP PROCESSING

A-1
A-1
A-2
A-2
A-2

SEARCH ALGORITHMS

B-1

WORD/BYTE SEARCHES (W OR N)
EFFECTIVE ADDRESS SEARCH (E)

B-1
B-1

3.10
3.11
3.12
3.13
3.14
3.14.1
3.14.2
3.14.3
3.14.4

CHAPTER

APPENDIX A
A.l
A.2
A.3
A.4
A.5
APPENDIX B
B.l
B.2

P~OCESSOR

3-25
3-26
3-28
3-28
3-32
3-33
3-34
3-34
3-35
3-36
3-37
3-37
3-37
3-37
3-38

Index-1

INDEX

FIGURES
FIGURE

1-1
3-1
A-I

ODT Communications and Data Flow
ODT Listing of Modes and Formats
Format of Processor Status Word

1-2
3-32
A-1

TABLES
TABLE

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

Common Elements of Keyboard Sequences
Forms of Address Expressions
ODT Characters/Symbols
Internal Register Access/Modification
Commands
Legal Radix-50 Characters and Numeric
Equivalents
ODT Error Codes

1-4
1-5
2-2
3-11
3-11

3-39
4-2

PREFACE

0.1

MANUAL OBJECTIVES AND READER ASSUMPTIONS

The intent of this manual is to enable its users to understand the
debugging techniques provided by ODT~
Readers are assumed to be
familiar with the information contained in:
1.

An appropriate PDP-II Processor
/34, /45, /55 or PDP-ll/70)
-

TRAX MACRO Reference Manual

The TRAX Linker Reference Manual

Handbook

(i.e.,

PDP-ll/04,

It is also important for readers of this manual to have gained an
understanding of the terminal device providing the primary operator
interface to the PDP-II processor. For example, on some terminals an
up-arrow may be present instead of a circumflex, and a back-arrow
instead of an underline character.
In presenting ODT, a tutorial format has been adopted that includes
explanatory text following actual ODT command sequences. Thus, the
flow of material throughout this manual is biased toward the user who
is encountering ODT for the first time.
Also, those terms and
expressions having particular significance in describing the functions
and operations of ODT are defined at appropriate points in the manual.

0.2

STRUCTURE OF THE DOCUMENT

Chapter 1 briefly describes the features of ODT and the functions of
the three maJor modules forming the program. Some of the important
operational aspects of aDT are described, and the common notation used
for describing all ODT command sequences is defined.
Chapter 2 presents the characters and symbols that form the vocabulary
of ODT/user communications. The significance of these characters and
symbols in a functional and operational sense is defined in this
chapter.
Chapter 3 describes the composition and function of all the ODT
command sequences available to the user for debugging purposes. It is
in this chapter that the explanatory text following the command
sequence examples has been employed.
Chapter 4 describes ODT's response to errors in the keyboard command
sequences and lists the error codes resulting from hardware-detected
errors during user program execution.

Finally, Appendix A and Appendix B present details of interest in the
Processor Status Word and the aDT search algorithms, respectively.

0.3

ASSOCIATED DOCUMENTS

Other manuals closely allied to the purposes of this document are
described
briefly
in
the
TRAX Documentation Directory.
The
appropriate Documentation Directory defines the intended readership of
each manual in the set for the host operating system, and provides a
brief synopsis of each manual's contents.

CHAPTER 1
INTRODUCTION

ODT operating under the TRAX kernel,
aids the user in debugging
assembled and linked object programs. Through keyboard interaction
with ODT, the user can:
Print the contents of any location in the object
examination or alteration.
Run all or any portion of an
breakpoint feature.

object

Search the object program for words
pattern.

program
having

Search the object program for instructions
specified address.

program

using
a

the

ODT

specified

bit

that

reference

Calculate offsets for PC-relative references
displacements within the object program.
Fill a specified block of words or
value.

bytes

with

for

and
a

branch

designated

List a specified block of words or bytes for examination.

1.1

ODT INTERNAL ORGANIZATION

Internally, ODT is modularized
provide three major functions:
1.

Command decoding

Command execution

Utility routines

into

independent

subroutines

that

The ODT command decoder routines interpret keyboard commands, check
for
command errors, save input parameters for use in command
execution, and transfer control to the appropriate ODT command
execution routines.
The command execution routines take the input parameters saved by the
command decoder routines and call the ODT utility routines to execute
the specified command. The command execution routines then exit to
the object program or return control to the command decoder routines
to await further keyboard input.

1-1

INTRODUCTION
The utility routines, used by both the command decoder and command
execution routines,
save and restore the contents of registers and
program locations and
perform
required
keyboard
input/output
operations.
The flow of control and data between the aOT
object program is illustrated in Figure 1-1.

routines

and

the

user

MANUALENTR~

BREAKPOINT
HANDLER

COMMAND
DECODER

PROGRAM
EXAMINATION &
MODIFICATION
COMMANDS

PROGRAM
ACTION
COMMANDS

INTERNAL
TABLE
MANIPULATION
COMMANDS

~------------------~
USER
PROGRAM

r---- ...
I

I
I

+
UTILITY

ODT
INTERNAL
TABLES

__________~~----------------~L..__R_O_U_T_IN_E_S__~--~~~TPUT
_ (I/O, ETC.)
~
'User Environment
Legend

ODT
- - - - - - - Flow of Control
- - - - - - - - - - Flow of Data

Figure 1-1

1.2

aOT Communications and Data Flow

OPERATIONAL DESCRIPTION

The following paragraphs describe the essential operational aspects of
aOT in the user environment.

1.2.1

Linking ODT into the User Program

At task-build time, aDT is linked to the user object program by the
Linker,
thus incorporating OOT into the overall task 1mage. The term
"task" or "task image," as used throughout this manual, refers to that
body of code resulting from Linker processing which can be loaded and

1-2

INTRODUCTION
executed directly. Once incorporated into the task image, ODT's
usefulness as a debugging tool stems from its ability to establish
selected breakpoints anywhere in the current memory-resident portion
of a user program.
ODT runs as part of the user task and does not affect overall system
operation.
Furthermore, it is executed with the same privileges and
at the same priority level as the task to which it is linked.
Multiple tasks, each linked to its own copy of ODT, can be debugged at
the same time, provided that sufficient memory and a terminal are
available for each active task.
For TST's, TSTBLD will link in ODT if you answer "YES"
mode question.

1.2.2

the

Debug

User Task Breakpoints

Breakpoints are user-selected locations at which execution is to be
halted temporarily to permit interaction with the user task and ODT.
Thus, ODT functions effectively as a monitor for the user task during
a debugging session.
When the user task is executed under ODT control, the original
contents of a breakpoint location are saved by ODT for later
restoration.
At the same time, ODT places a Breakpoint
Trap
instruction
(octal op-code 000003) in the breakpoint location. Up to
eight such breakpoint locations can be established in the user task at
any given time. Later, during the active debugging session, program
execution proceeds normally until a breakpoint location is reached.
The Breakpoint Trap
(BPT)
instruction is then executed, causing
control to be transferred to ODT. ODT then restores the original user
instruction to the breakpoint location and awaits any valid command
for a wide range of debugging operations.
Breakpoints must be set only in the first word of an instruction,
since the BPT instruction must be executed to cause the trap action
and the yielding of control to ODT.
After the desired debugging
operations associated with the current breakpoint have been performed,
the user issues an appropriate ODT command to continue execution. ODT
then resets all breakpoints to the BPT instruction (including the
current breakpoint), and continues task execution.
The assembly listing of the program under examination should be at the
terminal
for
reference
during
the debugging session.
Minor
corrections to the program may be made on-line. The program can then
be run under ODT control to verify any changes made. Major program
modifications, however, are more complex and should be noted on the
assembly listing.
In either case, all necessary changes should be
incorporated into the task image through
a
subsequent
edit,
reassembly, and relinking of the program.

1.2.3

Relocation Registers

When MACRO p~oduces a relocatable object module, the base address
of each program section in the module is relocatable 000000. The
addresses of all program locations, as shown in the assembly listing,
are therefore indicated relative to this base address. After the
module is linked by the Task Builder to physical memory locations (for
an unmapped system)
or to virtual memory locations (for a mapped
system), many values within the resulting object module will be biased

1-3

INTRODUCTION
by a constant whose value is the actual absolute base address of the
object module after it has been relocated. This constant is called
the relocation bias for the object module. Since a task may contain
several relocated object modules (each with its own relocation bias),
these biases must be continually subtracted from absolute addresses
during debugging operations in order to associate relocated code with
the assembly listing. aDT provides an automatic relocation facility
for calculating the relocation bias of each object module in a
relocatable program.
This facility is provided through eight relocation registers, numbered
o through 7, each of which may be set by the user to the relocation
bias of an object module at any given time during
debugging
operations.
The relocation bias of each program section in the task image is
obtained by consulting the memory map produced by the Linker. Once
set, a relocation register is used by aDT to relate the assembly
listing to the relocated code.
For a more detailed description of the linking and relocation process,
refer to the Task Builder reference manual for the host operating
system.

1.3

EXPRESSING ODT COMMANDS AND FUNCTIONS

In debugging operations, many aDT commands and functions are expressed
in keyboard sequences involving two or more characters. Such keyboard
sequences, having several
common
elements,
appear
frequently
throughout this manual.
For consistency, the notation in Table 1-1
has been adopted to facilitate the expression and understanding of all
user keyboard interaction with aDT. This notation is particularly
significant in Chapters 2 and 3.
Table 1-1
Common Elements of Keyboard Sequences
Meaning

Symbol
a

Represents an argument that is used
address of a task image location.

Represents an octal integer in the range 0 through 7.

Represents an octal value up to six digits in length,
with a maximum value of 177777(8), or an expression
which reduces to such a value.
If more than six
digits are specified, aDT takes only the last six
digits, truncated to the low-order 16 bits. The octal
value may be preceded by a minus sign, in which case,
the 2 1 s complement of the value is taken by aDT.

1-4

define

the

INTRODUCTION

The following examples illustrate how octal values (k) are interpreted
by ODT:
ODT
Interpretation

Symbol k
(Octal Value Typed)

1.3.1

000001

-1

177777 (2' s complement)

400

000400

-177730

000050 (2' s complement)

1234567

034567 (Truncated to low-order 16 bits)

Forms of Address Expressions

An address expression is always evaluated by ODT as a 16-bit
(six
octal digit) value. This address expression is represented throughout
this manual with the symbol a. An address expression may be typed in
anyone of three general forms, as described in Table 1-2.
Table 1-2
Forms of Address Expressions
Form of
Expression

Format of
Expression

Resulting Address
Expression (a)

Type 1

The value of
value of k.

Type 2

n,k

The value of (a) is the value of k,
plus the contents of relocation
register n, where n designates any
one
of
ODT's eight relocation
registers.
In this form,
k is a
relocatable
address.
If n is
greater than 7,
ODT
types
a
question
mark
(?)
character,
ignores the current command, types
the
underline
(_)
prompting
character, and awaits
a
valid
command. ODT recognizes only octal
numbers in defining address and
other
expressions.,
A
decimal
number (8 or 9) is illegal, causing
a question mark (?) to be printed
following the line in error.

(a)

simply

the

(continued on next page)

1-5

INTRODUCTION
Table 1-2 (Cont.)
Forms of Address Expressions

1.3.2

Form of
Expression

Format of
Expression

Resulting Address
Expression (a)

Type 3

C or
C,k or
n,C or
C,C

Whenever C is typed as an element
of an ODT command, ODT replaces
this character with the contents
of the constant register
(see $C,
Table 3-1)
and then evaluates the
expression as a Type 2 address
(n,k).
In other words, the value
in the constant register referenced
by the C command has the same role
as the n or k that it replaces in
an
address
expression.
For
example, when C is used in place of
n,
the
value in the constant
register
selects
a
relocation
register for use in printing out
task addresses (see Section 3.1).
In all cases where C is used in
place of n, the value of C must be
within
the range 0 through 7.
Whenever C is used in the place of
k,
the
value in the constant
register so referenced may be any
l6-bit
expression
value.
The
commands used in accessing
and
modifying
the
contents of the
constant register are described in
detail in Section 3.4 and Table
3-1.

Examples of Address Expressions

In the examples below of the three
values are assumed:

addressing

forms,

the

following

n = Relocation register 3, containing the value 003400.
$C

Constant register, containing the value 000003.

Form of
Expression

Address Expression (a)
Keyboard Input

ODT Octal
Interpretation

Type 1

000005

Type 1

-17

177761

Type 2

3,0

003400

Type 2

3,150

003550

Type 2

3,-1

003377

1-6

INTRODUCTION

Form of
Expression

Address Expression (a)
Keyboard Input

ODT Octal
Interpretation

Type 3

000003

Type 3

C,O

003400

Type 3

C,lO

003410

Type 3

3,C

003403

Type 3

C,C+C

003406

NOTE
For simplicity, most address expression
examples in this manual are Type 1; all
three types,
however,
are
equally
acceptable to ODT.

1-7

CHAPTER 2
ODT CHARACTERS AND SYMBOLS

User commands to ODT are composed of the characters and symbols
described below in Table 2-1.
This table summarizes all the ODT
commands in their available forms of use.
For the purposes of this
chapter, the reader should understand the notation presented in Table
1-1 and the basic concepts in the following paragraphs.
An open location is one whose contents have been printed by aDT for
user examination.
The value so printed is stored in a special
register called the quantity register
(see $Q, Table 3-1).
The
contents of an open location are available for change. A closed
location is one whose contents are not immediately available for
change.
Typing one of the commands listed below when it is preceded by an
address expression opens the addressed location and prints its
contents. The format of the printed output is a function of the
command so issued.
In other words, these are interpretive commands
which may be used to print the contents of a specified location in any
one or all of several formats (modes). When issued, these commands
leave the current location open for further operations.

/
\
"
%

(Word mode octal)
(Byte mode octal)
(Word mode ASCII)
(Byte mode ASCII)
(Word mode Radix-50)

Typing one of the seven
commands
listed
below
closes
the
currently-open location;
all but the carriage-return «CR» character
cause another location to be opened. The location so opened depends
on which of the other six commands is typed (see Table 2-1).
<CR> (Carriage Return)
<LF> (Line Feed)
(or up-arrow)
(or back-arrow)
@

In Table 2-1 and throughout this manual, the symbols <CR> and <LF> are
used to represent the pressing of the carriage-return and line-feed
keys, respectively.
As evident in the tables in this chapter, numerous aDT commands can be
entered in anyone of several forms. This flexibility stems from the
fact that aDT takes certain operational parameters and values from
tables within itself in performing specified commands. These tables
are described throughout this manual, particularly in Chapter 3, as

2-1

ODT CHARACTERS AND SYMBOLS

"ODT internal registers" or "ODT internal locations." These terms in
all cases refer to a block of memory within ODT which is reserved as a
temporary storage area for the dynamic debugging variables essential
to all ODT operations. These locations, consisting essentially of 17
sets of modifiable registers, are described in detail in Section 3.4.
If required parameters for a given operation have already been stored
in one or more of these internal locations as the result of a previous
operation, a shorter form of a given command may suffice for a current
operation, since ODT takes the current value of the relevant internal
location(s) in executing a specified command.
In the longer command
forms,
however, required values are an immediate part of the command.
The various command forms are summarized briefly in the tables
throughout Chapter 2. Chapter 3 treats the command forms in detail in
conjunction with the discussions of COT command sequences
and
functions.
Table 2-1
ODT Characters/Symbols
Format

+ or space

Meaning
Arithmetic operator.
Sum
the
preceding
argument and the following argument to form
the current argument.
Arithmetic operator. Subtract the following
argument from the preceding argument to form
the current argument.
Relocation register
operator.
Use
the
preceding I-digit octal value to reference
one of ODT's eight relocation registers; the
contents of this register and the value of
the argument following the comma form the
current argument.
Thus,
in ODT keyboard
commands, a comma separates a relocation
register specifier from an absolute value,
the combination of which is normally used to
specify relocatable address values in ODT
command sequences.

Radix-50 operator.
forming
Radix-50
3.16.4) •

This command is used in
arguments
(see Section

Current location
operator.
Causes
the
address
of.
the
last
explici tly-opened
location to be used as the current address
for ODT operations.
This is the address
assumed by the left angle bracket «) command
to return to the previous sequence of opened
locations (see Section 3.2.9). This address
is also implied in the use of the slash (/),
backslash (\), single quote ('), double quote
("), percent sign (%), and line-feed «LF»
commands.
(continued on next page)

2-2

ODT CHARACTERS AND SYMBOLS
Table 2-1 (Cont.)
ODT Characters/Symbols
Meaning

Format

Argument identifier.
Separates
multiple
arguments,
allowing an address expression or
ODT register value to be identified.
k

Represents any 6-digit octal value that
is
used as an argument in an ODT command.
The
symbol k also represents any expression which
reduces
to
a
6-digit
octal
value.
Expressions may include special arguments
(such as $n,
$x, C, or period) alone or in
combination with the arithmetic operators (+,
-,
comma,
or
*). Expression constructions
are terminated by typing a specific ODT
command character or a semicolon (i).

Represents an octal integer in the range from
o through 7. Decimal values are illegal in
ODT and are flagged with a question mark
(?)
immediately following the illegal value.

an
argument
whose
special
Represents
On
attribute is an address of a location.
value
specified
is
input,
any address
interpreted by ODT as a 6-digit octal value,
its
length.
Any
value
regardless of
exceeding this limit is truncated to the
On output, ODT always
low-order 16 bits.
prints an address value as six octal digits.

<CR) or
k<CR)

Close the currently-open location and
and the next command.
If <CR) is preceded by
k,
the value k replaces the contents of the
currently-open location before it is closed.

<LF) or
k<LF)

Close the currently-open location, open the
next sequential location and
print
its
contents.
If <LF) is preceded by k, the
value k replaces the
contents
of
the
currently-open location before it is closed.

Close the currently-open location,
open the
immediately-preceding location and print its
contents.
(The up-arrow appears on some
keyboards
and
is used in place of the
circumflex.) If ~ is preceded by k, the value
k replaces the contents of the currently-open
location before it is closed.

(continued on next· page)

2-3

CDT CHARACTERS AND SYMBOLS
Table 2-1 (Cont.)
CDT Characters/Symbols
Format

Meaning
Interpret the contents of the currently-open
location
as
a
PC-relative
offset and
calculate the address of the next location to
be
opened;
close
the
currently-open
location, and open and print the contents of
the
new
location thus evaluated.
(The
back-arrow appears on some keyboards and
is
used in place of the underline.)
If is
preceded by k,
the value k replaces the
contents
of
the currently-open location
before it is closed.

@ or k@

Interpret the contents of the currently-open
location as an absolute address, close the
currently-open location, and open and print
the contents of the absolute location thus
evaluated.
If @ is preceded by k, the value
k replaces the contents of the currently-open
location before it is closed.

> or k>

Interpret
the
low-order
byte
of
the
currently-open location as a relative branch
offset and calculate the address of the next
location
to
be
opened;
close
the
currently-open location and open and print
the contents of the relative branch location
thus evaluated.
If > is preceded by k,
the
value
k
replaces
the contents of the
currently-open location before it is closed.
The computation of this address is performed
by taking the
low-order
byte
of
the
currently-open location as a signed value,
multiplying this value by 2,
increasing the
result by 2,
and adding this sum to the
address of the currently-open location.

< or k<

Close the currently-open location (opened by
a
,
@, or > command) and reopen the word
location most recently opened by a /,
<LF>,
or~.
If the currently-open location was not
opened by a
, @, or >, then < simply closes
and reopens the current location.
If < is
preceded by k,
the value k replaces the
contents
of
the currently-open location
before it is closed.

Represents the address of one of eight user
program general registers, where n
is an
octal digit identifying RO through R7
(see
Section 3.3).
(continued on next page)

2-4

CDT CHARACTERS AND SYMBOLS
Table 2-1 (Cont.)
OOT Characters/Symbols
Format
$x or $nx

Meaning
Represents the address of one of 17 special
OOT internal register sets (see Section 3.4),
where x is one of the following alphabetic
characters,
and
n is an octal integer
identifying a given
location
within
a
register set.
These addressable register
sets exist within ODT in the following order:

Processor Status register
(hardware
PS), which is saved by OOT when a
breakpoint or user
program
fault
occurs

Search argument register

Search mask register

Low memory limit register

High memory limit register

Constant register

Quantity register

Format register

Reentry vector register

Breakpoint address registers.

Breakpoint proceed count registers.

Breakpoint instruction registers.

Relocation registers.

SST vector registers.

SST (synchronous system
contents registers.

Device control LUN
number) registers.

trap)

stack

(logical

unit

Constant register operator.
Represents the
contents of special register $C (constant
register).

Quantity register operator.
Represents the
contents of special register $Q (quantity
register).
(continued on next page)

2-5

ODT CHARACTERS AND SYMBOLS

Table 2-l (Cont.)
aDT Characters/Symbols
Format

Meaning

.. or a"

Word mode ASCII operator.
Interpret and
print the contents of the currently-open (or
the last previously-opened) location as two
ASCII characters, and store this word in the
quantity register ($Q).
If" is preceded by
a, the value a is taken as the address of the
location to be interpreted and printed.

or a l

Byte mode ASCII operator.
Interpret and
print the contents of the currently-open (or
the last previously-opened) location as one
ASCII character, and store this byte in the
quantity register ($Q).
If I is preceded by
a, the value a is taken as the address of the
location to be interpreted and printed.

% or a%

Word mode Radix-50 operator.
Interpret and
print the contents of the currently-open (or
the last previously-opened) location as three
Radix-50 characters, and store this word in
the quantity register ($Q).
If % is preceded
by a, the value a is taken as the address of
the location to be interpreted and printed.

/ or a/

Word mode octal operator.
Reprint
the
contents of the last word location opened,
and store this octal word in the quantity
register
($Q) •
If / is preceded by a, the
value a is taken as the address of a word
location to be opened and printed.

\ or a\

Byte mode octal operator.
Reprint
the
contents of the last byte location opened,
and store this octal byte in the quantity
register
($Q).
If \ is preceded by a, the
value a is taken as the address of a byte
location to be opened and printed.

Interpret and print expression value k as six
octal digits and store this word
in the
quantity register ($Q).

8 or 9,
RUBaUT,
or CTRLjU

Cancel the current command and await a new
command. The decimal value 8 or 9 is not a
legal character and thus, when
entered,
causes aDT to ignore the current command.

Remove all breakpoints from the user task.

Remove the nth breakpoint from the user task.

(continued on next page)

2-6

ODT CHARACTERS AND SYMBOLS
Table 2-1 (Cont.)
ODT Characters/Symbols
Format

Meaning

aiB

Set the next available sequential
in the user task at address a.

breakpoint

ainB

Set breakpoint n in the user task at

address

a.
K

Using the relocation register whose contents
are equal to or closest to (but less than)
the address of the currently-open location,
compute the physical distance
(in bytes)
between the address of the currently-open
location and the value contained in the
selected relocation registeri
print this
offset and store the value in the quantity
register ($Q).

Compute the physical distance
(in bytes)
between the address of the currently-open or
the last-opened location and
the
value
contained in relocation register ni print
this offset and store the value in the
quantity register ($Q).

ainK

Compute the physical distance
(in bytes)
between address a and the value contained in
relocation register ni print this offset and
store the value in the quantity register
($Q) •

F or kF

Fill memory locations within the address
limits specified by the low memory limit
register
($L)
and the high memory limit
register ($H) with the contents of the search
argument register ($A). If F is preceded by
k, the value k replaces the current contents
of $A before initiating the fill operation.

G or aG

Processing
commences
from
the
first
breakpoint by invoking G. Commencement from
subsequent breakpoints is invoked by a G.

aO or aikO

Calculate and print the PC-relative offset
and the 8-bit branch displacement from the
currently-open location to address ai
or
calculate and print the PC-relative offset
and the 8-bit branch displacement from the
specified address a to the specified address
k.

(continued on next page)

2-7

ODT CHARACTERS AND SYMBOLS
Table 2-1 (Cont.)
ODT Characters/Symbols
Format

Meaning

P or kP

Proceed with user program execution from the
current breakpoint location and stop when the
next breakpoint location is encountered or
the end of the program is reachedi
or
proceed with program execution from
the
current breakpoint location and stop at this
breakpoint only after encountering it the
number of times specified by integer k.

Set all relocation registers to -1,
highest address value, i.e., 177777(8).

Set relocation register n to -1, the
address value, i.e., 177777(8).

aiR

Set relocation register 0 to address value a.

ainR

Set relocation register n to address value a.

S or nS

Execute one instruction and print the address
of the next instruction to be executed; or
execute n instructions and print the address
of the next instruction to be executed.

W or kW
or miW
or mikW

Search
memory between
the address limits
specified by the low memory limit register
($L)
and the
high
memory limit register
($H)
for words with bit patterns which match
those of the search argument specified in the
search argument register ($A). Compare each
memory word and the search argument for
equality under the mask specified in the
search mask register
($M).
When a match
occurs, print the address of the matching
location and its contents.
If W is preceded
by k,
the value k replaces the current
contents of $A before initiating the search.
If W is preceded by m (identified by the
semicolon that follows
it),
the value m
replaces the current contents of $M before
initiating the search.
If W is preceded by both k and m, the current
contents of $A and $M are replaced with the
respective
values
so
specified
before
initiating the search.

the

highest

NOTE
Testing under a search mask
($M)
results in a comparison of the
memory word and the search argument
only in those bit positions which
correspond to the bits set to one
(1)
in the maski
all other bit
positions are ignored in the search
comparisons.
(continued on next page)

2-8

ODT CHARACTERS AND SYMBOLS
Table 2-1 (Cont.)
aDT Characters/Symbols
Format

Meaning

N or kN
or miN
or mikN

Search
memory between the address limits
specified by the low memory limit register
($L)
and the high memory limit register ($H)
for words with bit patterns which do not
match those of the search argument specified
in the search argument register ($A). This
search is identical in form and function to
the word
(W) search described above, except
that a test for inequality is performed.

E or kE.
or miE
or mi kE

Search memory between the address limits
specified by the low memory limit register
($L) and the high memory limit register ($H).
Examine these locations for references to the
effective address specified in the search
argument register
($A),
as masked by the
value specified in the search mask
register
($M) •
(The mask should normally be set to
177777 for the E command.)
Such references
may be equal to, PC-relative to, or a branch
displacement to the location specified in $A.
If E is preceded by k, the value k replaces
the current contents of $A before
initiating
the search.
If E is preceded by m, the
current contents of $M are replaced with the
value m before initiating the search.
If E
is preceded by both k and m,
the current
contents of
$A and $M are replaced with the
respective
values
so
specified
before
initiating the search.

L or kL
or aiL
or aikL
or niaikL

List all word or byte locations in the task
between the address limits specified by the
low memory limit register ($L) and the high
memory limit register,
using the listing
device specified in the device control LUN
register ($lD).
If L is preceded by k,
the
value k replaces the current contents of $H
before initiating the list operation.
If L
is preceded by a, the value a replaces the
current contents of $L before initiating the
list operation.
If L is preceded by both a
and k, the values a and k replace the current
co-ntents of $L and $H, respectively, before
initiating the list operation.
If L is also
preceded by the value n, this value selects
one of the device control LUN registers ($nD)
containing the logical unit number of the
device to be used in the list operation.
(continued on next page)

2-9

ODT CHARACTERS AND SYMBOLS
Table 2-1 (Cont.)
ODT Characters/Symbols
Format

Meaning

F or kF

Fill memory locations within the address
limits specified by the low memory limit
register
($L)
and the high memory limit
register ($H) with the contents of the search
argument register ($A).
If F is preceded by
k,
the value k replaces the current contents
of the $A register before initiating the fill
operation.

Enable ODT's handling of all SST vectors, and
write the addresses of ODT's trap entry
points into the table used by the SVDB$
Executive directive.
(See Table 3-1 for a
discussion of the SST vector
registers and
the $nV/ command.)

Exit from ODT and return control
to
Executive of the host operating system.

2-10

the

CHAPTER 3
COT COMMAND SEQUENCES AND FUNCTIONS

When OOT is initiated, its readiness to accept commands is indicated
through the underline
(_) prompting character (back-arrow on some
terminals) at the left margin of the terminal. Most COT commands can
then be issued in response to this character. This chapter describes
all the OOT command sequences and specific functions available to the
user.
Such keyboard interaction takes place using the characters and
symbols described in the preceding chapter.

3.1

PRINTING TASK ADDRESSES

Normally, when OOT prints user program addresses (as with the commands
<LF>, "', _, @, <, and », it attempts to print them in relative form
(Type 2, see njk, Table 1.2). If there is no relocation register
containing a value equal to the user task address to be printed, ODT
looks for the relocation register whose contents are closest to, but
less than, the address. It then represents that address relative to
the bias value contained in the register. However, if no relocation
register fits this requirement, the user task address is printed in
absolute form. Since the relocation registers are initialized to -1
(the highest address value), the user task addresses are initially
printed in absolute form.
If the contents of any relocation register
are subsequently changed, it may then qualify for use in determining
task addresses in relative form, depending on the OOT command issued.
For example, assume that relocation registers 1 and 2 contain the bias
values 1000 and 1004, respectively, and that all other relocation
registers contain much higher values. The following sequence might
then occur:,
_774/012345 <LF>
000776 /024145 <LF>
1,000000 /106421 <LF>
1,000002 /143164 <LF>
2,000000 /112713 <CR>

jOPENS ABSOLUTE
jOPENS ABSOLUTE
jOPENS ABSOLUTE
jOPENS ABSOLUTE
jOPENS ABSOLUTE

LOCATION 774.
LOCATION 776.
LOCATION 1000.
LOCATION 1002.
LOCATION 1004.

The printout format is controlled by the format register
($F).
Normally, this register contains a default value of 0 (see $F, Table
3-1), in which case, OOT prints addresses relatively
whenever
possible, as noted above.
The format register may be opened and
changed to a positive, nonzero value, howeverj
in this case, all user
task addresses are printed in absolute form.

3-1

ODT COMMAND SEQUENCES AND FUNCTIONS
3.2

COMMANDS FOR OPENING, CHANGING, AND CLOSING LOCATIONS

An open location is one whose contents have been printed by ODT for
examination and are thus available for change. A closed location is
one whose contents are not immediately available for change.
The contents of an open location may be changed by typing the new
value, followed by any ODT command which requires no argument (i.e.,
<CR), <LF), ", _, @, ), or <}. Note that leading zeros can be omitted
by the user.
Any command typed to open a location when another
location is already open, closes the currently-open location before
opening the new location.

3.2.1

Close Current Location:

<CR) or k<CR)

When the <CR) key is typed while a location is open, that location is
simply closed and no new location is opened. When <CR) is preceded by
an argument k, that value replaces the current contents of the
location before that location is closed. Typing the <CR) key has no
effect on ODT when no location is open.

3.2.2

Open Next Sequential Location:

<LF) or k<LF)

If the <LF) key is typed while a word location is open, i.e., if word
mode is in effect, ODT closes that location and opens the next
sequential word location, as shown below:
_1000/002340 <LF)
001002 /012740

iTHE <LF) KEY IS TYPED AFTER THE
iPRINTOUT OF 002340, OPENING THE NEXT
iLOCATION

In the example above, typing the <LF) key causes ODT to print the
address and the contents of the next location automatically. The
value 012740 is thus made available for examination and may be
modified by typing a new value before issuing any command which closes
the location.
If a byte location is currently open, i.e., if byte mode is in effect,
typing the <LF) key opens the next sequential byte location.
Repetitive execution of the <LF) command causes ODT to open successive
words or bytes, depending on the mode of the currently-open location.

3.2.3

Open Word Location:

/ or a/

A word location may be opened using the command form ai,
the address of the location to opened, as shown below:
_1000/012746

where

iOPENS ABSOLUTE LOCATION 1000.

After the user types the slash
{I}, ODT automatically opens the
addressed location and prints its 6-digit octal contents, making this
value available for examination or change.
If the contents of an open location are not to be changed, the user
may issue a <CR) command or any other command which closes an open
location, without first typing an argument k.
In the case of the <CR)
command, ODT then closes the currently-open location, performs a

3-2

ODT COMMAND SEQUENCES AND FUNCTIONS

carriage-return and line-feed action, and prints the
prompting
character
(_) to indicate its readiness to accept another command, as
shown below:

__ 1000/012746 <CR)

iCLOSES LOCATION 1000 AND AWAITS
iNEXT COMMAND.

To change the contents of an open location enter the new value
issuing a command that closes the location. For example:

_1000/012746 12345 <CR)

before

iMODIFIES LOCATION 1000 AND
iAWAITS NEXT COMMAND.

The slash command can also be used without an address argument to
reopen and reprint the contents of the word at the even-numbered
location last opened, as indicated in the following example:

_1000/012746 12345 <CR)
_/012345

iOPENS AND DISPLAYS CONTENTS OF
iPRECEDING WORD LOCATION.

This form of the slash command permits verification that a
was entered correctly in a preceding location.

new

value

The slash command may also be used in conjunction with the <LF)
command to open and print the contents of successive word locations.
After opening a location in word mode,
repetitive execution of the
<LF) command displays consecutive task locations, as shown below:

_1002/000123 <LF)
001004 /123456 <LF)
001006 /154321 <LF)
001010 /024351

iREPETITIVE <LF) COMMAND DISPLAYS
iCONSECUTIVE WORD LOCATIONS.

In the sequence above, the <LF) command closes the currently-open
location before opening the next location. The last <LF) command in a
series of such commands leaves the current location open for any
desired operation, as reflected above.
If an odd-numbered address is specified in opening a location, the
slash command causes the location to be opened in byte mode.
In this
case, ODT commands then issued operate on byte locations and values,
as indicated in the following sequence:

_1001/123 321 <CR)
-/321 <LF)
_001002 /021 <LF)
_001003 /010 <LF)
_001004 /201

iLOCATION 1001 OPENED IN BYTE
iMODE. SUBSEQUENT COMMANDS OPERATE
iON BYTE LOCATIONS.

Word mode can then be restored,
if desired, by
closing
the
currently-open byte location and opening another location on an even
address boundary, as shown below in the continuation of the preceding
sequence:

__ 001004 /201 <CR)
__ 1006/102054

i<CR) CLOSES CURRENT LOCATION.

iNEXT LOCATION OPENED ON WORD
iBOUNDARY, RESTORING WORD MODE.

3-3

ODT COMMAND SEQUENCES AND FUNCTIONS

3.2.4

Open Byte Location:

\ or a\

As noted in the preceding section, ODT also operates on byte locations
and values.
The command form a\ is provided in ODT for simplifying
the examination and modification of octally represented byte values,
including those that fallon odd address boundaries.
(On hard copy
terminals, the backslash is typed by holding down the SHIFT key and
typing L.) When this command form is used, the address value a,
specified prior to the command, may be either odd or even.
A byte
location may be opened, as shown below:
_1001\002

iLOCATION 1001 OPENED IN BYTE MODE.

After the user types the address of the byte location to be opened,
followed by the backslash
(\), ODT causes the contents of the
addressed location to be printed as a 3-digit octal value
(8 bit, .i.
377) •

If the contents of the byte location are not to be changed, the <CR)
command, or any other command which closes an open location, may be
issued without first typing an argument k.
In the case of the <CR)
command, ODT then closes the currently-open byte location, performs a
carriage-return and line-feed, prints the prompting character ( ), and
awaits another command, as shown below:
_1001\002 <CR)

iCLOSES LOCATION 1001 AND AWAITS

iNEXT COMMAND.
Should the user desire to change the contents of an open byte
location, he may do so by entering the new value before issuing a
command which closes the location, as reflected below:
_1001\002 10 <CR)

iMODIFIES LOCATION 1001 AND AWAITS
iNEXT COMMAND.

Similar to the slash (/) command, the backslash character may be used
without an address argument to reopen and reprint the contents of the
byte at the location last opened. This use of the byte command is
illustrated in the following sequence:
_1001\002 10 <CR)
_\010
Thus, the alteration of
verified.

iOPENS AND DISPLAYS CONTENTS OF THE
iLAST OPENED BYTE LOCATION.
a

previously-opened

byte

location

can

The <LF) command is also useful in conjunction with the backslash
command, permitting successive byte locations in the task to be
examined. After opening a location in byte mode, repetitive typing of
the <LF) command displays consecutive byte values, as shown below:
_1003\004 <LF)
001004 \120 <LF)
001005 \203 <LF)
001006 \310

iREPETITIVE <LF) COMMAND DISPLAYS
iCONSECUTIVE BYTE LOCATIONS.

The <LF) command closes the currently-open location before opening the
next locationi
the last such command issued, however, leaves the
current location open for any desired operation, as shown above.
If a word location is currently open, typing the backslash command
causes the word's low-order byte to be displayed without ODT leaving
word mode:
_1010/000005 \005

iDISPLAYS LOW-ORDER BYTE.
3-4

ODT COMMAND SEQUENCES AND FUNCTIONS

3.2.5

Open Preceding Location:

or k

If the circumflex (or up-arrow) key is typed when a location is open,
ODT closes the currently-open location and opens and prints the
contents of the immediately preceding location.
(On Teletypes, the
circumflex is typed by holding down the SHIFT key, and typing N. The
use of the circumflex is reflected in the following sequences:
_1000/002340 <CR)
_1002/012740

iLOCATION 1000 IS OPENED AND
iEXAMINED.
iLOCATION 1002 IS OPENED AND
iEXAMINED, FOLLOWED BY CIRCUMFLEX
iCOMMAND.
iPRECEDING LOCATION IS OPENED AND
iPRINTED.

001000 /002340
_0,232/005046 <LF)
0,000234 /012746

iLOCATION 232, RELATIVE TO RELOCATION
iREGISTER 0, IS OPENED AND EXAMINED.
iNEXT LOCATION IS OPENED AND PRINTED,
iFOLLOWED BY CIRCUMFLEX COMMAND.
iPRECEDING LOCATION IS OPENED AND
iPRINTED.

0,000232 /005046

If a byte location is currently open, issuing the circumflex command
opens the preceding byte location and makes its contents available for
examination or change, as shown below:
_1003\046 <LF)
001004 \003

iLOCATION 1003 IS OPENED IN BYTE
iMODE.
iNEXT BYTE LOCATION IS OPENED,
iFOLLOWED BY CIRCUMFLEX COMMAND.
iPRECEDING BYTE LOCATION IS OPENED
jAND PRINTED.

001003 \046
A

If the command form k is used, the expression value k modifies the
contents of the currently-open location before that location is
closed, as shown in the following sequences:
_0,230/005406 <LF)
0,000232 /000626 12345
0,000230 /005406 <LF)
0,000232 /012345

jLOCATION 230, RELATIVE TO RELOCATION
iREGISTER 0, IS OPENED.
jNEXT LOCATION IS OPENED AND
jMODIFIED TO CONTAIN 012345. FOLLOWED
jBY CIRCUMFLEX COMMAND.
jPRECEDING LOCATION IS OPENED AND
jPRINTED.
jCONTENTS OF MODIFIED LOCATION ARE
jVERIFIED.

If a location is not currently open, typing the circumflex command
opens, and prints the contents of the last previously-opened word (or
byte) location, as shown in the following sequence:
_0,236/000100 <CR)
0,000236 /000100

3.2.6

jRELOCATABLE ADDRESS 236 IS OPENED
jAND CLOSED.
jCIRCUMFLEX OPENS AND PRINTS LAST
jOPENED LOCATION.

Open PC-Relative Location: __ or k __

If the underline (or back-arrow) key is typed when a location is
currently open, the contents of that location are added to its
address+2 (PC value), yielding the address of the location to be

3-5

ODT COMMAND SEQUENCES AND FUNCTIONS
opened.
(On hard copy terminals, the underline is typed by holding
down the SHIFT key, and typing 0.) This computation is effectively a
PC-relative reference.
After this calculation, the current location
is closed, the new location is opened, and its contents are printed,
as shown in the following sequences:
_1000/000040 _
001042 /052470

iUNDERLINE OPENS PC-RELATIVE
iLOCATION AND PRINTS ITS CONTENTS.

If the currently-open location contains an odd value when the
underline command is issued, the referenced location is not on a word
boundary, and so is opened as a byte, as shown in the following
sequences:
_0,232/012345_
0,012601 /041

iPC-RELATIVE ADDRESS IS CALCULATED,
iCALCULATED ADDRESS IS THAT OF A
iBYTE.

_0,422/000001_
0,000425 /246

iSAME AS ABOVE.

When the command form k is used, the expression value k modifies the
contents of the currently-open location, and this new value is then
used in the calculation of the PC-relative address of the location to
be opened and printed, as shown in the following sequences:
0,232/012345 123456_

0,123712 /020301

3.2.7

Open Absolute Location:

iLOCATION 232; RELATIVE TO
iRELOCATION REGISTER 0, IS
iOPENED AND MODIFIED TO
iCONTAIN 123456, FOLLOWED BY
iUNDERLINE COMMAND.
iPC-RELATIVE LOCATION IS
iOPENED AND PRINTED.

@ or k@

The @ sign typed when there is a currently-open location takes the
contents of that location as the address of the next location to be
opened. The currently-open location is then closed, and the new
location is opened. The following sequences reflect the use of this
command:
_1006/001024 @
001024 /000500
100iR

_0,232/000456 @
0,000356 /005046

iUSES CONTENTS OF CURRENT
iLOCATION AS ADDRESS OF NEXT LOCATION
iTO OPEN.
iLOCATION 1024 IS OPENED AND ITS
;CONTENTS PRINTED.
iSETS RELOCATION REGISTER

° TO 100(8)

iSAME ACTION AS ABOVE, IN
iRELOCATABLE FORMAT.
iLOCATION 456 OPENED AND
iCONTENTS PRINTED.

If the command form k@ is employed, the expression value k modifies
the contents of the currently-open location, and this new value is
then taken as the address of the next location to be opened, as shown
in the following sequences:
_1006/001024 2100@
002100 /177774

iLOCATION 1006 IS MODIFIED TO
iCONTAIN 002100. THIS VALUE IS
iTHEN USED TO OPEN NEXT LOCATION.
3-6

ODT COMMAND SEQUENCES AND FUNCTIONS

_0,600/012345 12746 @

0,012356 /027117

iSET RELOCATION REGISTER 0 TO
iBIAS VALUE OF 370(8) FOR MODULE.
iCONTENTS OF RELOCATABLE ADDRESS 600
iARE MODIFIED TO CONTAIN 012746. THIS
iVALUE IS THEN USED TO CALCULATE
iADDRESS OF NEXT LOCATION TO BE
iOPENED.
iEVALUATED ADDRESS IS OPENED AND ITS
iCONTENTS PRINTED.

In the example above, note that the relocatable address of the next
location opened
(0,012356) is represented relative to the bias value
370(8) contained in relocation register O.
The accuracy of this
calculation is verified by adding the value 370(8) to the value
012356(8), yielding the sum 012746(8).

3.2.8

Open Relative Branch Offset Location:

> or k>

When the right-angle bracket
(»
command is issued for an open
location, ODT takes the low-order byte of this location to calculate a
relative branch offset in determining the address of the next location
to be opened.
The current location is closed when this command is
executed.
The relative branch offset, i.e., the address of the next location
be opened, is calculated as follows:
1.

Take the low-order byte of the currently-open
signed value.

Multiply this value by 2.

Add the result of Step 2 to the address of the
location+2 (PC value).

location

to
a

currently-open

The examples below show the use of the relative branch offset command:
_1032/000407 >
001052 /001456

iTAKES THE LOW-ORDER BYTE OF THE
iCURRENT LOCATION AS RELATIVE
iBRANCH OFFSET TO OPEN NEXT
iLOCATION.

_0,66/005046 >
0,000204 /000601

iSAME OPERATION AS ABOVE, EXCEPT
iRELOCATABLE ADDRESS VALUES ARE
iUSED.

If the command form k> is used, the expression value k modifies the
contents of the currently-open location, and the low-order byte of
this new value is then used in the calculation of the relative branch
offset location, as shown in the following sequences:
_1032/000407 301>
000636 /000010

_0,232/000456 134561
0,000576 /002340

iLOCATION 1032 IS MODIFIED TO
iCONTAIN 000301. LOW-ORDER
iBYTE OF THIS NEW VALUE IS
iTHEN USED IN DETERMINING RELATIVE
iBRANCH LOCATION.

iRELOCATABLE LOCATION 232 IS
iMODIFIED TO CONTAIN 134561. LOWiORDER BYTE OF THIS NEW VALUE IS
iTHEN USED IN CALCULATING RELATIVE
iBRANCH LOCATION.

3-7

aDT COMMAND SEQUENCES AND FUNCTIONS
Note in the first example above illustrating the k> command form, that
the byte value 301 is interpreted by ODT as a negative value (the
high-order bit in this byte is 1).
Therefore, a negative branch
offset results, causing location 636 (a lower physical address) to be
opened and its contents printed.

3.2.9

Return to Interrupted Sequence:

< or k<

The left angle bracket command «) can be used immediately after
issuance of any of the following address calculation commands:
1.

Open PC-relative location (_)

Open absolute location (@)

Open relative branch offset location (»

the

(see Section 3.2.6).

(see Section 3.2.7).
(see Section 3.2.8).

The user can issue any of these three commands
in any order after
explicitly opening a word location with a /, <LF>, or~.
The /, <LF>,
and ~ commands are explicit in that they open a specified location,
the word following a currently-open location, or the word preceding a
currently-open location, respectively.
They do not depend on the
contents of the open location as the address calculation commands
mentioned above do.
The left angle bracket command
«) causes ODT to
close
the
currently-open location,
and reopen the word location most recently
opened by a /, <LF>, or~.
If the currently-open location was not
opened by a
,@, or > command, then < merely closes and reopens the
current location itself.
The effect of the < command is reflected in the following sequences:
10000;R
0,1030/000174 <LF>
0,001032 /000200 @

000200 /007020 @
007020 /000000 <
0,001032 /000200
_1036/021346 ~
1034 /101036
102074 /000000 @
000000 /000000 >
000002 /000102 <
001034 /101036

;SETS RELOCATION REGISTER 0 TO 10000
;OPENS RELOCATABLE 1030; <LF> OPENS
iNEXT WORD
;@ OPENS LOCATION 200 IN ABSOLUTE
;FORMAT BECAUSE NO RELOCATION
;REGISTER'S CONTENTS ARE LESS THAN
;OR EQUAL TO 200
;@ OPENS 7020 IN ABSOLUTE FORMAT (NO
;RELOC. REG. CONTENTS < OR = TO 7020)
;< REOPENS RELOCATABLE 1032
;OPENS 1036; ~ OPENS PRECEDING WORD
;OPENS PC RELATIVE LOCATION.
;OPENS ABSOLUTE LOCATION.
;OPENS RELATIVE BRANCH OFFSET
iLOCATION.
;RETURNS TO LAST EXPLICITLY-OPENED
;LOCATION.
;OPENS AND PRINTS CONTENTS OF
iLOCATION 1034.

3-8

ODT COMMAND SEQUENCES AND FUNCTIONS
The contents of any location opened by one of the three address
calculation commands may be altered,
if desired, before issuing a
command which closes that location. This option is illustrated in the
following sequences:
_1064/000276 @
000276 /000340 336_
000636 /000000 302>
000444 /026474 474@
000474 /015325 <
001064 /000276

3.3

ACCESSING USER PROGRAM GENERAL REGISTERS:

ODT has a set of fixed locations which are used to store the current
values of the user program's general registers when a breakpoint
occurs. Thus, the current state of the user program is preserved so
that task execution can be resumed normally when control is returned
to the user through the execution of the G (Go)
or P
(Proceed)
commands
(see Section 3.6). These registers, numbered 0 through 7,
can be examined with a command of the following form:

where n represents an octal integer representing the desired register.
When the slash is typed, the contents of the specified register are
automatically printed by ODT, making this value available
for
examination or change. The user can change the contents of a general
register by issuing a command of the form $n/a <CR>, where n
represents the octal register specifier, and a represents the new
value to be entered.
The following examples show how the user
program's general registers are opened and modified:
_$0/000033 <CR>
_$4/000474 464 <CR>

iREGISTER 0 IS EXAMINED AND CLOSED.
iREGISTER 4 IS OPENED, MODIFIED TO
iCONTAIN 000464, AND CLOSED.

Any register modification just completed, as shown in the $4 line
above, can be verified by typing a slash in response to ODT's
prompting character. Thus, the continuation sequence is:
_/000464

iPRINTS THE CONTENTS OF THE
iPREVIOUSLY-OPEN LOCATION.

Note that the <LF>, A, __ , or @ command may be used in connection
a user program general register when that register is open.

3.4

ACCESSING SPECIAL ODT INTERNAL REGISTERS:

with

$x or $nx

ODT contains a number of fixed locations which are used as registers
for temporary storage of values essential to debugging operations.
In
addition, these registers provide a mechanism through which the
current state of the user program is preserved when a breakpoint
occurs, saving and restoring such values as the Processor Status Word
and the user program stack pointer during debugging operations. These
internal registers, which are accessible to the user in the same
manner as any location within the task image, are described in detail
in Table 3-1.

3-9

ODT COMMAND SEQUENCES AND FUNCTIONS
The command form $x/ is used to access an ODT internal register, where
x represents the alphabetic register identifier. The processor status
register, for example, can be accessed with the following command:
_$S/OOOOll

iTHE COMMAND $S/ OPENS THE STATUS
iREGISTER AND PRINTS ITS CONTENTS.

In response to the $S/ command, ODT prints the 16-bit Processor Status
Word in 6-digit octal format.
If desired, any new value can be
entered into the register, followed by a command which closes the
register.
The command form $nx/ is used to access an internal register set
consisting of several separate locations, where x represents the
alphabetic register identifier (as above), and n represents an octal
integer referencing a particular location within the register set.
Relocation register 7, for example, can be accessed with the following
command:
-$7R/000040

iTHE COMMAND $7R/ OPENS RELOCATION
iREGISTER 7 AND PRINTS ITS CONTENTS.

if desired, by
The contents of this register may also be modified,
entering the new value and issuing a command which closes the
location.
All the ODT internal registers described in Table 3-1 can be
and modified in similar fashion.

accessed

Note in Table 3-1, that the values a, k, or n may appear in connection
with the generic command forms used to open the ODT internal registers
(e.g., $C/a, $F/n, $A/k, etc.). These symbols represent new values
that may be entered into the register if the current value displayed
upon opening the register is not desired. Also, these symbols may be
used in connection with other ODT commands (described in Table 3-1 and
elsewhere throughout this manual) which automatically enter parameters
into specific internal registers without overtly opening the locations
to which these parameters apply.
The symbols a,
k, and n are
described in the context of the operation being performed and, in all
cases, represent the specific parameters or arguments defined by the
user to serve current debugging purposes.

3-10

ODT COMMAND SEQUENCES AND FUNCTIONS

Table 3-1
Internal Register Access/Modification Commands
Function

Processor status register.
Contains the Processor
Status Word after the execution of the last user
program instruction prior to the occurrence of the
breakpoint.
Although this register is accessible to
the user through the $S/ command,
it is set by the
Executive of the host operating system and normally
should not be changed by the user.
This register
provides the mechanism through which the Processor
Status Word may be examined during a debugging session.
For a detailed description of the Processor Status
Word, refer to Appendix A.

Constant register. Set by the user to any 16-bit value
representing an address (a) or an expression value (k)
through the $C/a <CR> or the $C/k <CR> commands,
respectively.
Both command forms are identical in
function and are shown to represent the possible uses
of the values so entered.
For example, any value
entered in the constant register may be used by typing
C as an argument in an aDT command. The possible uses
of this value are illustrated as a Type 3 address in
Table 1-2.
The constant register is described in
further detail in Section 3.16.2.

Format register. Set by the user to an octal value (n)
through the $F/n <CR> command. When set to zero (the
default value), all user task addresses are printed by
aDT in relative form when appropriate (as described in
Section 3.1). All other values of n cause user task
addresses to be printed in absolute form.

Search mask register. Set by the user to a word or
byte search mask value through the $M/m <CR> command.
A mask value may also be set in those commands which
initiate search operations (see Sections 3.8.1 through
3.8.3). This register is initialized by aDT to minus
one
(-1),177777(8). Thus, unless otherwise modified,
all bit positions in the search argument (see $A below)
and the memory word/byte will be compared in a search
operation.

Search argument register.
Set by the user to a
word or byte search argument (k) through the $A/k <CR>
or the $A\k <CR> commands,
respectively.
A search
argument may also be set in those commands which
initiate search operations (see Sections 3.8.1 through
3.8.3) •
(continued on next page)

3-11

ODT COMMAND SEQUENCES AND FUNCTIONS
Table 3-1 (Cont.)
Internal Register Access/Modification Commands
Register

Function

Low memory limit register.
Set by the user to an
address value
(a)
through the $L/a <CR) command,
establishing the lower memory limit for all aDT search,
list,
and
fill
operations which reference this
register. This register is initialized by aDT to zero
(0). Either absolute or relocatable address values may
be entered into this register.

High memory limit register. Set by the user to an
address value
(a)
through the $H/a <CR) command,
establishing the upper memory limit for all aDT search,
list,
and
fill
operations which reference this
register. This register is also initialized by aDT to
zero
(0). As with the $L register, either absolute or
relocatable address values may also be entered into
this register.

Quantity register. Set automatically by aDT to the
last value printed on the console. This register is
described in further detail in Section 3.16.3.

Reentry vector register. This register is normally set
to one
(1)
by the user through the $X/n <CR) command
when an initial debugging pass has been completed, thus
allowing the user program to be executed directly
without again reentering aDT. If set to one
(1),
the
task then starts at its normal entry-point address or
at the address specified by the user
in general
register 7
(see Section 3.3),
rather than at aDT's
starting address.
The use of this
register
is
described in further detail in Section 3.17.

$nR

Relocation register n.
One of eight
(n)
register
locations which may be set by the user to a value (a)
through the ainR command or the $nR/a <CR) command.
A
value set in a specified register location represents
the relocation bias of a given relocatable object
module of interest during the debugging session. Once
set, the contents of a given location enable aDT to
print user task addresses relative to a base address.
Both positive and negative offsets
(biases)
can be
calculated by aDT using these register locations (see
Section 3.11). Also, when the user opens a given
location in a relocatable module,
the value in the
associated relocation register enables aDT to calculate
the relocated address of the user task location (see
Section 3.12). Thus, relocatable code in the assembly
listing can easily be associated with the addresses of
relocated code during the debugging session.
This
register
is initialized by aDT to minus one (-1),
177777 (8) •
(continued on next page)

3-12

ODT COMMAND SEQUENCES AND FUNCTIONS
Table 3-1 (Cont.)
Internal Register Access/Modification Commands
Function

Breakpoint address register n.
One of eight
(n)
locations which may be set by the user to an address
value (a) through the aiB or ainB commands (see Section
3.5) or the $nB/a <CR) command. These user-specified
addresses identify breakpoint addresses in the user
task
whose contents are to be swapped with BPT
instructions in an associated breakpoint instruction
register (see $nI below). This swapping process occurs
upon execution of the G command when the debugging
session is initiated or upon execution of the P command
when task execution is resumed from a breakpoint
location
(see Section 3.6).
The breakpoint address
registers are described in further detail in Section
3.5.

$nD

Device control LUN register n.
One of three
(n)
locations which may be set by the user to a value (k)
through the $nO/k <CR) command, where the values
defined for nand k have the following significance:
Value k

Value n

- User terminal device logical unit number
(see Note below). The value of k in this
location ($00) is normally 000007(8).

- Console listing device logical unit number
(see Note below). The value of k in this
location ($10) is normally 000010(8).

- QIO event flag number - The value of k in
this location
($20) is normally a default
value of 000034(8).
NOTE
The user terminal device LUN
(TI:)
and the
console list device LUN (CL:) are assigned by
the Linker, which examines the UNITS= Keyword
option
(having a default value of 6). The
LUN n+l is assigned to the user terminal
device, and the LUN n+2 is assigned to the
console list device, where n is the default
value 6 or the value used as the argument to
the
UNITS= Keyword
option.
Thus,
$00
normally contains 000007(8), and $10 normally
contains 000010(8).

$nI

Breakpoint instruction register n. One of eight
(n)
locations which may be set by ODT to contain BPT
instructions. These BPT instructions are swapped with
user program instructions at the breakpoint locations
(continued on next page)

3-13

· ODT COMMAND SEQUENCES AND FUNCTIONS
Table 3-1 (Cont.)
Internal Register Access/Modification Commands
Register

Function

$nI
(cont.)

defined through the breakpoint address register
(see
$nB above).
This swapping
process
occurs
upon
execution of the G command when the debugging session
is initiated or upon execution of the G or P command
when task execution is resumed from a
breakpoint
location
(see Section
3.6).
This
register
is
initialized by OOT to BPT instructions, i.e., op code
000003(8) .

$nG

Breakpoint proceed count register n. One of eight
(n)
locations which may be set by the user to a proceed
count value (k) through the kP command or the $nG/k
(CR) command.
The proceed count value set in each of
these locations is associated with a given breakpoint
address,
as defined by the user
in the breakpoint
address register (see $nB above).
It is sometimes
useful,
for
example,
to set a breakpoint in a loop.
After the breakpoint occurs, the user may type the kP
command
(see Section 3.6)
to resume execution.
The
program then executes through the loop k number of
times before again recognizing the breakpoint.
Each
time the breakpoint location is encountered,
the
proceed count value in the associated register location
is decremented. When the count reaches zero
(0),
the
breakpoint is again recognized, suspending user task
execution and transferring control to OOT for
any
desired
debugging
operations.
This register
is
initialized by OOT to one (1).

$nV

SST vector register n. One of eight (n) locations that
contain entry-point addresses of OOT routines
for
handling synchronous system traps.
These traps occur
during user program execution as a result of certain
hardware-detected errors and programming conditions.
The value n refers to a given SST vector address
location, as listed below.
Each of these locations
contains a pointer to an OOT error-handling routine
which evaluates the SST error condition and prints out
an appropriate console error message (see Section 4.2).

If a user program and OOT both have SST vectors enabled
for a condition that then occurs, OOT receives the
trap.
As released, ODT has seven vectors enabled.
Only vector number
6
(TRAP instruction executed) is
OOT's handling of vector 6 can be enabled by
I disabled.
the user through the V command. The V command enables
ODT's handling of all SST vectors,
and writes the
addresses of OOT's trap entry points into the table
used by the SVOB$. Executive directive
(see
the
Executive Reference Manual of the host system).
$nV

Value n

SST Vector Register
- Odd address reference in word
instruction.
(Also,
on some POP-II processors
(e.g.,
POP-ll/45) ,
the execution of an
illegal
instruction
is trapped here rather than
through SST vector 4.)
(continued on next page)
3-14

ODT COMMAND SEQUENCES AND FUNCTIONS

Table 3-1 (Cont.)
Internal Register Access/Modification Commands
Register
$nV
(Cont. )

Function
SST Vector Register

Value n
1

2
3
4

5
6

- Memory protect violation

(segment fault).
- T-bit trap or BPT instruction executed.
- lOT instruction executed.
- Reserved or illegal instruction executed.
- NON-TRAX EMT in~truction executed.
- TRAP instructic..,1 executed.

These vector locations are accessible to the user
through the $nV/ command in a manner similar to any
other ODT internal register, where the value n selects
one of the eight locations listed above. Normally,
these ODT locations are not manipulated by the user.
However, the user has the option of handling some or
all of the SST traps (except the BPT instruction)
that
may occur during program execution.
In this case, the
user may set the corresponding SST vector location in
ODT to zero
(O), thereby causing the user program to
trap to an SST processing routine within itself,
i.e.,
the trap will reference the user SST vector address
directly without invoking ODT control. Such an option
obviously
assumes that the user program contains
appropriate routines for handling SST error conditions.
$nE

3.5

SST stack contents register n.
One of three
(n)
locations
(where n is equal to 0, 1, or 2) into which
the top three items on the user program stack are
placed when a synchronous system trap occurs (see $nV
above).
These stack items have different values,
depending on the type of trap taken.
(Consult the
Executive Reference Manual of the host operating system
for a discussion of synchronous system traps.) These
locations, containing user task information of interest
following an SST interrupt, can be examined through the
$nE/ command, where n selects one of the three register
locations, as noted above.

TASK BREAKPOINT COMMANDS:

aiB, ainB, B, or nB

Breakpoints must be set in the first word of an instructiop. When set
through one of the commands described below, ODT places the address of
each breakpoint location in an associated breakpoint address register
(see $nB, Table 3-1).
When a G or P command is issued to initiate or resume task execution
(see Section 3.6), ODT swaps the user instructions in the specified
breakpoint locations with BPT instructions
in
the
breakpoint
instruction registers
(see $nI, Table 3-1). Later, as a breakpoint
location is encountered during task execution, the BPT instruction in
that location causes control to be transferred to ODT at the address
contained in SST vector register 2 (see $nV, Table 3-1).
The BPT instruction,
in connection with
facilities,
thus serves as a simple and

3-15

the
PDP-II
hardware
efficient mechanism for

OOT COMMAND SEQUENCES AND FUNCTIONS
calling a debugging aid.
As the final
consequence
of
this
software-generated trap, ODT suspends task execution and restores the
original user instruction to the breakpoint location.
Since ODT
retains control, the user can then perform any desired debugging
operations from the current breakpoint location.
It is important to note that the original user instruction is always
restored to the current breakpoint location when the breakpoint trap
occurs, ensuring that all user task instructions will be executed
during the course of a debugging session if the program is allowed to
proceed to completion.
It should also be noted that debugging overlaid tasks presents special
considerations
in
setting
and maintaining breakpoints.
Since
breakpoints established for the current segment do not remain valid
for a subsequent segment, all breakpoints should be removed from the
current segment before a new segment is loaded.
Otherwise, task
instructions saved from breakpoint locations in the current segment
will later be swapped into a new segment, thus implanting invalid
instructions
and
corrupting
the program.
It is recommended,
therefore, that tasks be non-overlaid for debugging.
Up to eight breakpoints, numbered 0 through 7, can be set at any given
time. The command which accomplishes this action takes the form:
ajB

where a represents the address of the breakpoint location. Repetitive
execution of this command can be used to establish all eight (0
through 7) breakpoint locations, since each of the addresses so
defined is entered sequentially into the breakpoint address registers
(see $nB, Table 3-1).
Specific breakpoints can be
command:

set

changed

through

the

following

ajnB

where a represents the address of the desired breakpoint location, and
n represents one of eight (0 through 7) such specific breakpoints.
The examples below illustrate how breakpoints are set and changed:
_B

_1020jB
_1030jB
_1040;B
_1032;lB

;CLEAR ALL BREAKPOINTS.
;SET BREAKPOINT O.
;SET BREAKPOINT 1.
jSET BREAKPOINT 2.
;RESET BREAKPOINT 1.

The B command typed alone removes all breakpoints in the user task, as
shown in the initial command of the preceding sequence. The command
form nB removes only the specified breakpoint, as shown in the last
command below, where n represents anyone of the eight (0 through 7)
breakpoints currently in effect. The following sequence shows how
breakpoints are set, changed, and removed:
_1020;OB
_1030;lB
_1064;2B
_1220j3B
_1324;4B
_1032jlB
_3B

;SET BREAKPOINT 0 AT LOCATION 1020.
;SET BREAKPOINT 1 AT LOCATION 1030.
;SET BREAKPOINT 2 AT LOCATION 1064.
;SET BREAKPOINT 3 AT LOCATION 1220.
;SET BREAKPOINT 4 AT LOCATION 1324.
jCHANGE BREAKPOINT 1 TO LOCATION
;1032.
jREMOVE BREAKPOINT 3.

3-16

ODT COMMAND SEQUENCES AND FUNCTIONS
The command form $nB/ references the address of the nth breakpoint, as
stored in the nth breakpoint address register (see $nB, Table 3-1).
Assuming that the previous command sequence is still in effect,
the
user may reference breakpoint 0 through the following command.
_$OB/00l020

iOPENS BREAKPOINT REGISTER 0 SET IN
iPREVIOUS SEQUENCE.

The command $nB/ thus opens breakpoint address register n, causing its
contents to be printed. Continuing with the current command sequence,
the user may examine the contents of successive breakpoint address
registers by repetitively typing the <LF> key, as shown below:
_$OB/00I020
$lB /001032
$2B /001064
$3B /000364

iOPENS BREAKPOINT O.
iBREAKPOINT 1, OPENED BY LINE FEED.
iBREAKPOINT 2, OPENED BY LINE FEED.
iBREAKPOINT 3, OPENED BY LINE FEED.

All eight breakpoint address registers can be examined in this manner.

3.6

PROGRAM EXECUTION COMMANDS:

G or aG and P or kP

Two general command forms are available for running the user task:
the G (Go) command and the P (Proceed) command. An alternate form of
each command is also available which takes an argument, as described
in the following paragraphs. The G command exists primarily to begin
program execution at the user task's transfer address, and the P
command is used to resume program execution at the next logical
instruction after a breakpoint has occurred.
When the G command is executed, the BPT instructions in the breakpoint
instruction registers
(see $nI, Table 3-1) are swapped with the user
instructions in the task image locations defined in the breakpoint
address registers (see $nB, Table 3-1). Task execution then begins at
the program's entry-point address, i.e., the address contained in the
user task's program counter (PC).
If an address argument a is specified with the G command, the swapping
of BPT instructions and user task instructions at breakpoint locations
occurs as described above, but program execution begins at the
specified task address.
For example, the command:

initiates execution at task location 1000.
Note that any address
argument used with the G command must specify an even address, i.e., a
word location boundary.
The program runs until a breakpoint is
encountered or until the end of the program is reached.
(A program
that is in an infinite loop must be aborted and then restarted.)
When a breakpoint is encountered, the contents of the user task
general registers are stored in ODT locations $0 through $7 (see
Section 3.3). In addition, task execution is suspended, the user
program instructions are restored to all breakpoint locations, and ODT
prints a console message indicating the occurrence of a breakpoint.
This message takes the following form:
nB:a
where n represents the breakpoint number, and a represents the address
of the breakpoint location. The prompting character ( ) then appears

3-17

ODT COMMAND SEQUENCES AND FUNCTIONS
on the following line to indicate ODT's readiness to accept any
command, as shown in the sequences below:

_1010i3B
_lOOOG
3B:00IOIO

valid

iBREAKPOINT 3 IS SET AT LOCATION
il010.
iEXECUTION IS STARTED AT LOCATION
ilOOO.
iEXECUTION STOPS AT BREAKPOINT 3, AND
iTHE ADDRESS OF THE BREAKPOINT
iLOCATION IS PRINTED.

To continue program execution from a
breakpoint location,
the user
types either the -aG, P or kP command. Thus, the G or P command can
be used without an argument, if program execution is to be resumed
after a breakpoint occurs.
If program execution is interrupted by the
occurrence of an error of the type BE, 10, EM, TR, or FP (see Section
4.2), use of the G or P command causes execution to resume at the word
location following the error
location,
rather than at the error
location itself.
The P command is illegal if a breakpoint has not yet occurred.
If
this
command is
issued before a breakpoint location has been
encountered, ODT responds with a question mark
(?)
on the line
in
error and prompts with the underline character (or back-arrow) on the
following line, indicating that the user must issue the G (Go) command
to begin or resume program execution.
If the task has not yet been run, the G command starts execution at
the program's entry-point
(transfer)
addressi
otherwise,
the G
command causes program execution to resume immediately following the
last logical
instruction executed.
In this case, the G command has
the same effect as the P command when resuming execution from a
breakpoint location.
When the G or P command is executed, the user general registers
(see
Section 3.3)
are restored to their original (pre-breakpoint) values,
the 8PT instructions are swapped with the user instructions referenced
by the breakpoint address registers, and control is returned to the
user program.
When a breakpoint is set within a loop, it may be desirable to allow
the program to execute through the loop a specified number of times
before recognizing the breakpoint.
This can be done through an
alternate form of the P command which takes an argument k, where k is
an octal integer specifying the number of times the breakpoint is
to
be encountered before program execution is suspended.
If the P
command is issued without an argument, execution continues only to the
nex~ breakpoint (or to the end of the program).
The breakpoint proceed count is associated only with that breakpoint
which has most recently occurred, i.e., a different proceed count is
associated with each breakpoint, determining the number of times each
breakpoint is to be encountered before program execution is suspended,
as shown in the example below:
3B:00IOIO

_1250i5B

_3B:00IOIO

iEXECUTION IS HALTED AT BREAKPOINT 3.
iBREAKPOINT 5 IS SET AT LOCATION
"i1250.
iEXECUTION IS CONTINUED, LOOPING
iTHROUGH BREAKPOINT 3 SIX TIMES,
iHALTING ON THE 7TH OCCURRENCE OF THE
iBREAKPOINT.
iEXECUTION IS HALTED AT BREAKPOINT 3,
iODT PRINTS BREAKPOINT MESSAGE AND
iAWAITS A COMMAND.
3-18

ODT COMMAND SEQUENCES AND FUNCTIONS
The breakpoint proceed counts can be inspected by typing a command
the form:

where n represents the octal identifier for the breakpoint proceed
count register
(see $nG, Table 3-1). After the slash (/) is typed,
ODT prints the contents of the specified register. The user may type
the <CR> key to close the location (leaving the count unchanged), or a
new count may be entered through the command $nG/k <CR>, where k
represents the new count to be entered. Still another alternative is
to type the <LF> key repetitively to examine the values in subsequent
(or all)
breakpoint proceed count registers. The following sequence
shows how the proceed counts are examined and changed:
_$OG/OOOOOI 15 <LF>
$lG /000001 <LF>
$2G /000001 <LF>
_3G /000005 <CR>

3.7

iPROCEED COUNT FOR BREAKPOINT 0 IS
iEXAMINED, MODIFIED TO 15, FOLLOWED
iBY LINE-FEED COMMAND.
iPROCEED COUNT ~OR BREAKPOINT 1 IS
iEXAMINED, FOLLOWED BY LINE FEED
iCOMMAND.
iPROCEED COUNT FOR BREAKPOINT 2 IS
iEXAMINED, FOLLOWED BY RETURN
iCOMMAND.

SINGLE-INSTRUCTION MODE COMMANDS:

S or nS

A command has been provided in ODT to allow the user to step through
the execution of the program one instruction at a time, if desired.
An alternate form of this command takes an argument, allowing the user
to specify the number of instructions to be executed before task
execution is again suspended.
When the single-instruction mode is in effect, breakpoints are not
present in the user task. Rather, task execution is suspended as a
result of setting the T-bit in the Processor Status Word (see Appendix
A)
as the user instruction is executed. Thus, when executing the S
command without an argument, each user instruction encountered is
trapped to suspend execution. If the S command is being used with an
argument, however, the trap occurs, but ODT does not suspend task
execution until the specified instruction count has been completed, as
described in the following paragraphs.
The command for the single-instruction mode takes the form nS, where n
represents an octal integer specifying the number of user task
instructions to be executed before control is returned to ODT.
If n
is omitted, an argument of 1 is assumed. When the instruction count
(n) is completed, ODT suspends task execution and prints a message of
the form 8B:a, where a represents the address of the next instruction
to be executed. The following sequence illustrates the use of this
command:

8B:00lOOO

iSETS INSTRUCTION COUNT, ESTABLISHES
iSINGLE-INSTRUCTION MODE, AND
iINITIATES TASK EXECUTION.
iINDICATES THAT INSTRUCTION COUNT HAS
iBEEN COMPLETED, TYPES OUT ADDRESS OF
iNEXT INSTRUCTION TO BE EXECUTED.

3-19

ODT COMMAND SEQUENCES AND FUNCTIONS
If ODT is currently representing task addresses relative to a
relocation register, note (for reasons stated in Section 3.1) that the
terminal message for single instruction mode takes the form 8B:n,a.
The value n represents the octal register specifier indicating the
relocation register whose contents are closest in value to the address
of the last instruction executed, and the value a represents the
6-digit octal address which must be added to the contents of
relocation register n
(i.e., the relocation bias of the module in
question) to determine the actual relocated address of the location
being displayed.
The following command sequence illustrates this
principle:
_101200ilR
_1,105 2 iB

OB:l,001052
_S

8B:l,001056
_S

8B:l,001062

iSETS RELOCATION REGISTER 1
iTO THE VALUE 101200.
iSETS BREAKPOINT 0 RELATIVE
iTO CURRENT VALUE OF
iRELOCATION REGISTER 1.
iSETS BREAKPOINT IN TASK AND
iINITIATES TASK EXECUTION.
iBREAKPOINT 0 OCCURS.
iINITIATES SINGLE-INSTRUCTION MODE.
iADDRESSES OF NEXT INSTRUCTION
iTO BE EXECUTED ARE REPRESENTED
iAS VALUES WHICH MUST BE BIASED BY
iCONTENTS OF RELOCATION REGISTER 1.

In the example above, to determine the relocated address of the next
instruction to be executed, the user must add the values 1056 and
1062, respectively, to the relocation bias 101200 in relocation
register 1, thus yielding relocated address values of 102256(8) and
102262 (8) .

3.8

SEARCH OPERATIONS

Allor any specified portion of memory within the task's partition can
be search~d for word or byte locations which contain specific bit
patterns. A second type of search can also be initiated which
examines memory locations for words which reference a specified
location in the user task.
The following sections describe these
search operations.
(See also Appendix B, Search Algorithms.)

3.8.1

Word/Byte Search Commands:

W, kW, miW, or mikW

Before initiating a word search, several preconditions must be
established:
(1)
the search limits must be definedi
(2) the search
mask must be establishedi and (3) the search argument itself must be
specified.
The search limits are defined through address values entered into the
low memory limit regsiter
($L)
and the high memory limit register
($H), as noted in Table 3-1. If, after opening the low memory limit
register with the $L/ command, the current 6-digit octal value being
displayed is not desired, the user may enter any new value appropriate
to the intended search operation. The desired address value in the
high memory limit register may be established in like fashion after
first opening the register with the $H/ command.

3-20

ODT COMMAND SEQUENCES AND FUNCTIONS
As reflected in the command forms below, either
absolute
relocatable task addresses can be set in the $L and $H registers:
$LjOOOOOO 1000
$LjOOOOOO 1,1000

iSETS $L TO ABSOLUTE ADDRESS.
iSETS $L TO RELOCATABLE ADDRESS.

$HjOOOOOO 2000
$HjOOOOOO 0,2000

iSETS $H TO ABSOLUTE ADDRESS.
iSETS $H TO RELOCATABLE ADDRESS.

When relocatable address values are specified in the search limit
registers,
the apparent values in $L and $H are effectively augmented
by the value of the relocation bias for the object module.
The search mask is specified in the search mask register
($M).
The
command which accomplishes this action is described under $M in Table
3-1. Bits set to 1 in the mask define corresponding bit positions in
the search argument (see below) and the memory words (or bytes) which
will be compared during the search operationi
bits not set to 1 in
the mask cause the corresponding bit positions in the search argument
and the memory words (or bytes) being searched to be ignored in all
compare operations.
The search argument is specified in the search argument register ($A).
The command which accomplishes this action is also described in Table
3-1 under $A. Note that either a word or byte search argument value
can be specified.
The discrete actions described above
establish
the
necessary
preconditions for
initiating search operations. These actions are
reflected in the first four lines of the OOT command sequence in the
example.
At this point,
the user need only type the W command in
order to initiate the search, as shown in the fifth line of the
examploe.
If a desired mask already exists, however, as a residual parameter
from a previous search operation or as the result of an overt action
in preparing for a new search operation, the user may initiate the
search through a command of the following form:
kW
where k represents the desired search argument.
In using this command
form,
note that the value preceding the W command is taken by aDT as
the search argument, not the search mask.
On the other hand, if a desired search argument already exists as a
result of the actions noted above, the user may initiate the search
operation through a command of the following form:
miW
where m represents the desired search mask.
A more convenient method of initiating search operations, however,
is
to specify the search mask and the search argument as part of a
multi-element ODT command.
Assuming that the search limits have
already been specified in the $L and $H registers (as described
above), the user may simply type a command in the following form:
mikW
where m represents the search mask ($M), and k represents the search
argument
($A).
Typing W then initiates the search operation without
further
intervention.
When a match
occurs,
i.e.,
when
the

3-21

ODT COMMAND SEQUENCES AND FUNCTIONS
corresponding bit positions in the search argument and the memory word
being compared agree under the specified mask, ODT prints the address
of the matching location and its contents.
The search operation is conducted in either
depending on the mode of the last open command.

word

byte

mode,

In the search process, an exclusive OR (XOR)
is performed with the
word
(or byte) currently being examined and the search argument. The
result of this comparison is then ANDed with the specified search
mask.
If the result is zero, a match occurs. ODT then types the
address and the contents of the matching location, as shown throughout
the example below.
The following command sequences illustrate both word and
operations:
_$M/177777 177400 <CR)
_$L/OOOOOO 1000 <CR)
_$H/OOOOOO 1400 <CR)
_$A/OOOOOO 600 <CR)
_W
001010 /000770
001034 /000404
_377iW

001020 /000200
_213W

001032 /000213
_$A\213 200 <CR)
_5W

byte

iSET MASK TO TEST HIGH-ORDER BYTE.
iSET LOW LIMIT SEARCH ADDRESS.
iSET HIGH LIMIT SEARCH ADDRESS.
iSET WORD SEARCH ARGUMENT TO 600.
iINITIATE WORD SEARCH OPERATION.
iPRINT ADDRESS AND MATCHING WORD.
iPRINT ADDRESS AND MATCHING WORD.
iCHANGE MASK TO TEST LOW-ORDER
iBYTE AND INITIATE SEARCH.
iPRINT ADDRESS AND MATCHING WORD.
iCHANGE SEARCH ARGUMENT TO 213 AND
iINITIATE SEARCH.
iPRINT ADDRESS AND MATCHING WORD.
iSET BYTE SEARCH ARGUMENT TO 200.
iCHANGE BYTE SEARCH ARGUMENT TO 5 AND
iINITIATE SEARCH.

If the user specifies a mask having zeros throughout,
locations within the search limits are printed by ODT.

all

The word/byte search algorithm
Appendix B.

detail

3.8.2

described

Not This Word/Byte Search Commands:

further

memory
in

N, kN, miN, or mikN

This search works exactly the same as the word search described above,
except that words (or bytes) which do not match are printed. Thus, a
test for inequality is performed on all memory words/bytes
in the
specified search range.

3.8.3

Effective Address Search Commands:

E, kE, miE, or mikE

ODT also searches for memory locations containing -instructions which,
when executed, effectively result in a reference to a specified task
address. After first defining the search limits in the $L and $H
registers,
as described in Section 3.8.1 above, the effective address
search may be initiated by typing the following command:
mikE
where m represents the search mask, and k represents the search
argument.
The values m and k are entered automatically in the search
mask register
($M)
and
the
search
argument
register
($A),
respectively, when the mikE command is issued.
3-22

ODT COMMAND SEQUENCES AND FUNCTIONS
As is the case with word/byte search operations described in Sections
3.8.1 and 3.8.2, the command forms used to initiate an effective
address search depend on which of the required ODT internal register
values currently exist. For example, if the required register values
are specified in discrete steps, as shown in the first four lines of
the command sequences below, the effective address search can be
initiated by typing only the E command. If the desired search mask
value exists, however, as the result of prior action, the command
form:
kE
suffices to initiate search operations, where k represents the search
argument.
If, on the. other hand, the desired search argument exists
as a result of prior action, the command form:
miE

may be used to initiate the search,
mask.

where

In an effective address search,
printed by ODT:

following

the

represents
types

Words which contain an absolute
argument itself) j

address

Words which contain a relative address
the specified search argument addressj

Words which contain a relative branch
specified search argument address.

(i.e.,
offset
and

the

words
the

reference

are

to
the

Note that since references to k, an effective address, are being
searched for, normal usage of this command requires that the mask
register be set to 177777j otherwise, the effective address will be
modified.
The command sequences and ODT responses in an effective address search
are illustrated in the example below:
_$M/OOOOOO 177777 (CR)
_$L/OOOOOO 400 (CR)
_$H/OOOOOO 100400 (CR)
_$A/OOOOOO 1034 (CR)

001016 /001006
001054 /002767
_1020E
001022 /177774
001030 /001020

jSET MASK TO COMPARE ALL BITS.
jSET LOW LIMIT SEARCH ADDRESS.
jSET HIGH LIMIT SEARCH ADDRESS.
jSET EFFECTIVE ADDRESS SEARCH
jARGUMENT TO 1034.
jINITIATE EFFECTIVE ADDRESS SEARCH
jOPERATION.
jPRINT RELATIVE BRANCH LOCATION AND
jCONTENTS.
jPRINT RELATIVE BRANCH LOCATION AND
jCONTENTS.
jINITIATE A NEW SEARCH FOR REFERENCES
JTO LOCATION 1020.
jPRINT RELATIVE ADDRESS OFFSET
jLOCATION AND CONTENTS.
jPRINT LOCATION CONTAINING ABSOLUTE
jADDRESS 1020.

Particular attention should be given to the reported references to the
effective address, because a word may have the specified bit pattern
of an effective address without actually being referenced in the
program.
ODT reports all occurrences of a possible effective address
reference.

3-23

ODT COMMAND SEQUENCES AND FUNCTIONS
3.9

FILL COMMANDS:

F or kF

The search argument register (see $A, Table 3-1)
can be used in
conjunction with the F command to set a block of memory to a specified
value.
While the most
commonly-used
value
is
zero,
other
possibilities are +1, -1, ASCII space, etc. Before a block of memory
can be initialized to a given value, the limits of the memory area to
be filled must be defined through the low memory limit register ($L)
and the high memory limit register ($H).
Consult table 3-1 for a
description of the commands which store address values in these
registers.
The initialization value may be stored in the search argument register
(see $A, Table 3-1)
as a discrete step.
It is more convenient,
however, to specify this value in the initialization command itself,
which takes the following form:
kF
This command automatically stores the initialization value k in the
search argument register ($A) and initiates the fill operation. ODT
then stores this value into successive memory words or-bytes, starting
at the address specified in the low memory limit register ($L) and
ending with the address specified in the high memory limit register
($H) •
The initialization command fills the specified memory range with words
if the last open command was performed in word mode; correspondingly,
the specified memory range is filled with byte values if the last open
command was performed in byte mode.
For the examples below, assume that the
contain the following values:
Relocation register 1

1000

Relocation register 2

2000

Relocation register 3

3000

listed

relocation

registers

The command sequences below might then occur.
The first fill
operation sets word locations 1000 through 1776 to zeros (0), while
the second operation sets byte locations 2000 through 2777 to ASCII
spaces.
_$L/OOOOOO 1,0 <CR)
_$H/OOOOOO 2,-2 <CR)
_$A/123456 0 <CR)
_F

_$L/OOIOOO 2,0 <CR)
_$H/001776 3,-1 <CR)
_$A\OOO 40 <CR)

iSET LOW MEMORY LIMIT TO 1000.
iSET UPPER MEMORY LIMIT TO 1776.
iSET SEARCH ARGUMENT REGISTER TO O.
iFILL SPECIFIED MEMORY BLOCK WITH
iZEROS.
iCHANGE LOW MEMORY LIMIT TO 2000.
iCHANGE UPPER MEMORY LIMIT TO 2777.
iOPEN SEARCH ARGUMENT REGISTER IN
iBYTE MODE AND CHANGE ITS CONTENTS TO
iOCTAL 40 (ASCII SPACE).
iFILL BYTES IN SPECIFIED MEMORY BLOCK
iWITH SPACES.

3-24

ODT COMMAND SEQUENCES AND FUNCTIONS
In a fill operation, the memory limits must be defined through
discrete actions which deposit the desired address values in the low
memory limit register ($L) and the high memory limit register
($H).
The only argument that can be specified as an element of the fill
command is the fill value itself. When so specified, this fill value
establishes the initial contents of the search argument register ($A)
or modifies its current contents before initiating the fill operation.
If the fill value is not specified when the F command is issued, ODT
takes the current contents of $A in performing the fill operation.

3.10

OFFSET CALCULATION COMMANDS:

aO or aikO

Relative addressing and branching involve the use of an offset,
i.e.,
the
number
of
words or bytes forward or backward from the
currently-open location to the effective address. During a debugging
session, it may be desirable to change a relative address or branch
reference by replacing an existing instruction offset with another
value.
OOT calculates and prints instruction offsets in response to
the commands described below.
The aO command causes ODT to calculate and print the PC-relative
offset and the branch displacement from the currently-open location to
a specified address. Thus, the aO command is equivalent in function
to the command .ikO, where the dot (.) represents the currently-open
location (see Section 3.16.1), and k represents the specified address.
The following sequences illustrate the use of the aO command:
_16126/001402 161340 __ 000004 >000002 <CR>
-1034/103421 10460 __ 000010 >000004 <CR>
In using the aO command form, it is assumed that a location is already
open, as shown in the example above. Thus, the user need only specify
the desired address to be used in calculating the offsets from the
current location.
After typing the 0 character, ODT calculates the
offsets and prints the results on the same line.
The PC-relative
offset is flagged with the underline ( ) or back-arrow character, and
the branch displacement is flagged with the right angle-bracket
(»
character.
The aikO command causes ODT to calculate and print the PC-relative
offset and the branch displacement from one specified address to
another. In this command form, the symbol a represents the first
address, and k represents the second address.
The following sequences illustrate the use of this command form:
_16126i161340 __ 000004 >000002 <CR>
_1034/103421 1022;10340 __ 000010 >000004 <CR>
_1022il0340 __ 0000l0 >000004 <CR>

In the first line of the examples above, the first address (16126)
is
specified, followed by a semicolon (i) and the second address (16Y34).
After typing the 0 character, ODT calculates the offsets and prints
them in the same manner as in the aO command above. The remaining
examples follow this same pattern.
Note in the command form aikO that it need not be issued in connection
with an open location.
Since both address values are explicitly
specified, the address of the currently-open location has no implied

3-25

ODT COMMAND SEQUENCES AND FUNCTIONS
effect in the calculation of the offset values.
examples above illustrate this principle.
The command form aikO is also useful in
values, as shown below.

The second and third

calculating

negative

offset

_1022;10340_ 000010 >000004 <CR>
_1034;10220 __ 177764 >177772 <CR>
The first example calculates a positive offset value, while the second
sequence calculates a negative value. It is often desirable to know
the PC-relative offset and the branch displacement values from a
higher
memory
address to a lower memory address,
since many
instructions in the normal flow of program logic result in a transfer
of control in the negative direction.
In either command form (aO or a;kO), note that the location for which
offsets have been calculated remains open for further operations. For
example, if the user wants to change the offset value in the low-order
byte of the instruction word, he may do so as shown in the following
sequence:
_1034/103421 11320 __ 000074 >036 1034\021 36 <CR>
_/103436
Note that location 1034 is first opened in word mode.
If, after
calculating the offsets, the user desires to change the value of the
low-order byte, byte mode must first be established for that location;
the command 1034\, as shown in the example above, is essential to this
purpose. Unless byte mode is established for the current location,
any value then entered is interpreted as a word value. The net result
in that case is the obliteration of the instruction op-code in the
high-order byte.
If the user wishes to verify the alteration of the offset value, he
may do so by typing the slash (/) command on the succeeding line, as
shown above.

3.11

RELOCATION REGISTER COMMANDS:

ainR, aiR, nR, or R

The function of the relocation registers is described in Section 1.2.3
and in Table 3-1.
At the beginning of a debugging session, these
registers are preset to the relocation biases of the relocatable
modules of interest during the debugging session.
Relocation registers are initialized to -1 (octal 177777, the highest
possible memory address), so that unwanted registers do not enter into
the selection process when ODT searches for the most appropriate
relocation register for
its address calculations. When relocation
registers are set to -1, all task image addresses reference either
absolute physical memory locations (for non-mapped systems) or virtual
memory locations (for mapped systems).
A relocation register is set by typing the desired bias value,
followed by a semicolon and the specification of one of the eight
relocation registers, as shown below:
a;nR
The symbol a represents an address expression,
integer from 0 through 7.

3-26

and

represents

ODT COMMAND SEQUENCES AND FUNCTIONS

The following command form may also be used:

aiR
In this case, relocation register 0 is assumed to be specified, since
the register specifier has been omitted. In contrast to the command
form aiB for the breakpoint address registers described in Section
3.5, however, the repetitive execution of the command form aiR does
not enter values serially into the relocation registers.
Therefore,
the command form ainR must be used to enter a bias value into a
specific relocation register other than register O.
To set all relocation registers to -1, the following command is typed:

iSETS ALL RELOCATION REGISTERS
iTO -1, 177777(8).
To set a specified relocation register to -1, a command in the form nR
is used, where n represents an octal register specifier, as shown
below:

jSETS ONLY RELOCATION REGISTER 3 TO
j-l,177777(8).

To set a specified relocation register to a desired value, a command
in the form ajnR is used, where a represents the desired value, and n
represents the octal register specifier, as shown below:
_1000j5R
_5,100j5R

jSETS RELOCATION REGISTER 5 TO 1000.
jEFFECTIVELY ADDS 100 TO THE CONTENTS
jOF RELOCATION REGISTER 5.

Position-independent code may be loaded into address space other than
that to which it was linked. When a program is loaded into address
space below that at which it was linked, the appropriate relocation
bias is the 2's complement of the apparent downward displacement. One
method for easily evaluating this bias and storing it in the
relocation register is illustrated below.
Assume, for example, that the program was linked to location 5000 and
then moved downward to location 1000. The following command sequence
would then be used:
_lOOOjlR
_1,-5000jlR

jSETS RELOCATION REGISTER 1 TO 1000.
jCHANGES RELOCATION BIAS TO ACTUAL
jDOWNWARD DISPLACEMENT.

The last command above stores the 2's complement of 4000 in relocation
register 1, as desired.
An alternate method of establishing the downward displacement might be
the following command sequence:
_$OR/177777 1000-5000 <CR) jOPENS RELOCATION REGISTER 0 AND
jSETS RELOCATION BIAS TO ACTUAL
jDOWNWARD DISPLACEMENT.
_/174000
jSLASH COMMAND PRINTS RELOCATION
jBIAS IN PREVIOUSLY-OPENED LOCATION.
ODT maintains a table of relocation register locations, beginning with
$OR. These locations may be opened through a command of the following
form:

3-27

ODT COMMAND SEQUENCES AND FUNCTIONS
The symbol n represents an octal digit specifying which one of the
eight locations is to be opened. Such locations may be opened and
modified in the same manner as any other register location,
as shown
in the following sequence:
_$3R/00IOOO <LF)

iRELOCATION REGISTER 3 IS OPENED.

iTHE <LF) COMMAND OPENS RELOCATION
$4R /002000 <LF)

iREGISTER 4.

$5R /004000 <CR)
_$3R/00IOOO 1040 <CR)

iOPENS RELOCATION REGISTER 5. THE
i<CR) COMMAND ENDS SEQUENCE.
iOPENS RELOCATION REGISTER 3 AND
iCHANGES ITS CONTENTS TO 1040.

_6000;6R

A SECOND <LF) COMMAND

iSETS RELOCATION REGISTER 6 TO 6000

iAND ENDS SEQUENCE.

3.12

RELOCATION CALCULATOR COMMANDS:

ainK, nK, or K

When a location has been opened, it is often desirable to associate
the relocated address of that location with its relocatable value.
To calculate the relocatable address of a given location relative to a
particular relocation bias, the user types a command in the following
form:

ainK
The symbol a represents the relocated address
relocatable address is to be calculated,
relocation register specifier (0 through 7).

value from which
and n represents

the
the

The K command is effective in conjunction with opened word and byte
locations.
For example,
if the command elements a and
are not
specified, the currently-open location is assumed to be operative
(i.e.,
.,
is assumed).
Thus,
the command 3K is equivalent in
function to the command .i3K (see Section 3.16.1).
If the relocation register specifier n is omitted,
the relocation
register whose contents are equal to, or closest to (but less than)
the currently-open location is automatically selected by ODT for use
in calculating the relocatable address.
In the example below,
relocation register 2, which contains 2000, meets this requirement:
_2500iK

2,000500

iCALCULATES RELOCATABLE ADDRESS.

Thus, ODT's response to the K command consists of the octal identifier
(2)
of the relocation register used in the calculation, followed by
the relocatable address value
(000500)
of the specified relocated
address (2500).

3.13

LISTING COMMANDS:

L, kL, aiL, aikL, or niaikL

A number of command forms are available for listing a block of memory
locations within the user task's partition. The particular command
form used in initiating a listing operation depends on whether the
required ODT register values exist as the result of prior action or
whether they must be specified overtly as an argument in the listing
command itself.
In either case,
the following ODT registers must
contain the user-specified values required fdr the intended listing
operation:

3-28

ODT COMMAND SEQUENCES AND FUNCTIONS
1.

The beginning address of the memory range to be printed must
be deposited in the low memory limit register (see $L, Table
3-1).

The ending address of the memory range to be printed must be
deposited in the high memory limit register (see $H, Table
3-1).

The logica~ unit number of the listing device must be
deposited ln the device control LUN register (see $nD, Table
3-1). The appropriate values for the device control LUN
registers ~re normally established by the Task Builder.
Therefore, the user need not be concerned with any explicit
ODT operations in establishing or altering these values. The
default values for these registers are described in detail in
Table 3-1.
Normally, device control LUN register 0 ($OD)
contains the logical unit number of the user terminal device
(TI:), while device control LUN register 1 ($lD) contains the
logical unit number of the console listing device (CL:).

Assuming that the necessary register values described above exist as
the result of prior action,
the user need only type the L key to
initiate a listing operation:
iPRINTS MEMORY LOCATIONS WITHIN
iSPECIFIED ADDRESS LIMITS USING
iCONSOLE LISTING DEVICE (CL:).
If the desired address value presently exists in the low memory limit
register
($L)
and the user wishes either to establish the required
value for the high memory limit register ($H) or to modify its current
contents, the following command form is used:
iTAKES ADDRESS VALUE "k" AS ENDING
iLOCATION AND INITIATES LISTING
iOPERATION.
Conversely, if the desired address value presently exists in the high
memory limit register ($H) and the user wishes either to establish the
required value for the low memory limit register ($L) or to modify its
current contents, the following command form is used:
iTAKES ADDRESS VALUE "a" AS
iBEGINNING LOCATION AND INITIATES
iLISTING OPERATION.
If neither of the required address values presently exist
$H, the following command form is used:

and

iTAKES ADDRESS VALUES "a" AND "k"
iAS THE BEGINNING AND ENDING
iADDRESSES, RESPECTIVELY, AND
iINITIATES THE LISTING OPERATION.
Finally, a fourth command form is used if none of the required values
presently exist. In this case, all the discrete values required for a
listing operation must be specified as arguments in the listing
command itself, as shown below:
_niaikL

iALL LISTING CONTROL ARGUMENTS
iARE SPECIFIED IN SINGLE
iLISTING COMMAND.

3-29

ODT COMMAND SEQUENCES AND FUNCTIONS

The command form above uses the logical unit number contained in the
specified device control LUN register n ($nD) to print all memory
locations within the specified address limits a and k. Any value for
n other than zero
(0)
or one (1) is treated by ODT as though the
console listing device ($lD) was specified, i.e., the default value
for n is one (1).
The address values a and k specified as arguments in the listing
command may be either absolute or relocatable in form.
It is
advisable, however, when debugging relocatable program segments,
to
use relocatable address expressions in defining the memory limits in
$L and $H for listing operations. By so doing, the task addresses
printed out by ODT during the listing of the specified memory block
can be associated directly with the relocatable addresses in the
assembly listing.
Any address values so specified, whether absolute
or relocatable, cause corresponding values to be entered into the
memory limit registers when the L command is executed. The use of
relocatable address values, however, assumes that an appropriate
relocation bias for the object module in question has been established
in ~ne of the eight available relocation registers. For example,
if
an object module has a relocation bias of 370(8), the following
command sequence might be used in initiating a listing operation:

_0,370iR <CR>
_0,1020iO,1040L

iSETS RELOCATION REGISTER 0 TO
iRELOCATION BIAS FOR DEBUGGING THE
iMODULE.
iINITIATES THE LISTING OF THE MEMORY
iBLOCK BETWEEN RELOCATABLE TASK
iADDRESSES 1020 AND 1040.

The beginning address in the resulting listing will
then
be
represented in relocatable form, i.e., 0,001020, as will the ending
address.
In listing a block of memory, it is important to note that the listing
format is governed by the mode of the previous open command.
In other
words, the interpretation of each memory location and the format of
the listing output are determined by the last output mode used by ODT.
In this connection, two general output listing modes are available, as
described below:
1.

Word mode octal. Established through opening a word location
through the slash (I) command (see Section 3.2.3) or any other
command which opens a location and causes its entire 6-digit
octal value to be printed.

Byte mode octal. Established through opening a byte location
through the backslash (\) command (see Section 3.2.3) or any
other command which opens a byte location and causes its
3-digit octal value to be printed.

A sequence of operations which results in the printout
and byte locations is shown in Figure 3-1.

Three other listing options are available to
establishing alternate modes, as described below:

user

the

both

word

through

Word mode ASCII.
Established through
interpreting
the
contents of a location using the double-quote (") character
before issuing the listing command.
For
example,
the
representative expression 0,1020", as shown in Figure 3-1,
establishes word mode ASCII before the listing operation is
initiated.

3-30

ODT COMMAND SEQUENCES AND FUNCTIONS

Byte mode ASCII.
Established through
interpreting
the
contents of a location using the single-quote (I) character
before issuing the listing command. As shown in Figure 3-1,
the representative expression 0,1020 1 establishes byte mode
ASCII before the listing command is issued.

Word mode Radix-50.
Established through interpreting the
contents of a location using the percent sign (%) before
issuing the listing command. This listing option is invoked
through the representative expression 0,1020%, as shown in
Figure 3-1.

Note that the address expressions referenced in Items 1 through 3
above are intended to be illustrative only. Any means of establishing
the desired output mode before issuing the listing command is
permissible.
In all cases of ODT listing output, the first line starts with the
beginning octal address of the memory block being printed, followed by
the contents of eight consecutive word or byte locations.
Subsequent
lines consist of the beginning octal address of the next eight
consecutive locations, etc.

3-31

ODT COMMAND SEQUENCES AND FUNCTIONS

)F'RE
ODT : ... PRE

_110400iR
_$L/990800 9,94522
_fH/898e80 9,04622
_L
9,094522 /929195 e9988(1 8£1£1980 8280(10 0471(11 (12~H (14 054524 042520
9,894542 /941440 951101 (142522 £13:7124 046451 £152517 052116 944449
9,894562 1959116 852125 95184£1 846117 046525 £12(1105 £100(180 (100008
9,884692 /929090 947101 82(1194 954524 842520 04144£1 051181 B42522
9,894622 /037124
_0,94522\105 L
0,894522 \195 048 999 9(1£1 £te0 B(1B 000 04£1
0,994532 \101 116 194 (148 124 131 129 195
0.894542 \940 103 191 122 122 195 124 e76
9.,884552 \851 115 117 125 11t. 124 949 111
0,994562 \116 129 125 124 949 126 117 114
8, 994572 \125 115 195 B4B BBB 9£10 000 geB
0,894682 \909 949 181 116 184 848 124 131
9,884612 \128 195 84£1 193 191 122 122 195
9,884622 \124
_8,94522" E L
0,884522 "E
9,884532 ,. A N [)
T \' F' E
9,884542
C A R R E T )
O,884552 " ) M 0 U N T
I
..,. 0 L
9,884562 " N F' U T
9,8&4572 "u M E
9,884682. ,.
A N D
T 'T'
9,884612 I F' E
C A R R E
9,894622 .. T
_8,84522"E
9,884522 "E
AN D T'T' F'E
9,884542 " C A~: R£ T) )fif (Ill NT
9.984562 "NP UT V OL LIM E
9. 994692 "
AN D T'T' PE
C AR f':E
9.894622 "T)
_8, 04522;{EFU L
9,884522 ;~EFU
ED2 LT3 EFT NK. KC:X:
9,894542 f!J/X MF&! KCZ 186 L"3 I'IY9 "Sir' K.
9,994562 r!L38 1'15/ 1'11H LHO LN7 EFlI
9,984682 f!ED2 LT3 EFT Nle KCX J /:x: "F(;! KCZ
9,994622 ;nS6

Figure 3-1

3.14

ODT Listing Modes and Formats

REPRINTING OPEN LOCATIONS

It is often desirable to print the contents of an open location in a
mode other than that in which it was opened or to print its contents
in other than 6-digit octal format.
The commands described below, all
of which cause the word or byte value to be stored in the quantity
register ($Q) when printed, are available for this purpose.
An important operational characteristic of ODT should be noted in
connection with the use of the interpretive commands described below
and the <LF) command. As pointed out in Section 3.13, ODT has five
distinct output modes, as follows:

3-32

ODT COMMAND SEQUENCES AND FUNCTIONS
1.

Word mode octal C/) ;

Byte mode octal C\) ;

Word mode ASCII C") ;

Byte mode ASCII CI ) ;

Word mode Radix-50 C%) •

and

When a location is opened in anyone of these output modes, ODT
"remembers"
(saves) the mode of the location just opened/interpreted.
Although the user may then issue any other interpretive commandCs)
on
the same line, when the <LF) command is entered to close that
location, ODT opens the next sequential location in the mode of the
previous location.
In other words, after a location is opened or
interpreted, the output mode thus established, prevails for all
subsequent <LF) commands. The following command sequences illustrate
this principle:
_0,234\346 IF <LF>

000235 \025 <LF>
000236 \100 <CR>
_lOOO"AB 'A <LF>
001002 "CD <LF)
001004 "EF <CR)

:RELOCATABLE LOCATION 234 OPENED IN
:BYTE MODE OCTAL AND INTERPRETED IN
jBYTE MODE ASCII, FOLLOWED BY <LF)
jCOMMAND.
jNEXT SEQUENTIAL LOCATION OPENED
jIN BYTE MODE.
jSAME AS ABOVE.
jCONTENTS OF LOCATION 1000 INTERPRETED
jIN WORD MODE ASCII AND BYTE MODE
jASCII, FOLLOWED BY <LF) COMMAND.
jNEXT SEQUENTIAL LOCATION INTERPRETED
jIN WORD MODE ASCII.
jSAME AS ABOVE.

_0,232/034567 IW "W9 %IGI <LF) jRELOCATABLE LOCATION 236
jOPENED IN WORD MODE OCTAL AND
jINTERPRETED IN BYTE MODE ASCII, WORD
jMODE ASCII, AND WORD MODE RADIX-50,
jFOLLOWED BY <LF) COMMAND.
0,000234 /000624 <LF)
jNEXT SEQUENTIAL LOCATION OPENED IN
:WORD MODE OCTAL.
0,000236 /000100 <CR>
jSAME AS ABOVE.
Although the examples above are general in nature and do not
illustrate the use of all the output modes, the principle so
demonstrated applies to all the interpretive commands described in
Sections 3.14.1 through 3.14.4. For convenience, these examples are
presented in this section, rather than being repeated in context with
the discussions below.

3.14.1

Print Octal Byte Value:

Typing the backslash (\) command when a word location is currently
open causes ODT to interpret and print the low-order byte of the word
as three octal digits, as shown below:
_0,20/044520 \120

jPRINTS LOW-ORDER BYTE IN
jCURRENTLY-OPEN WORD LOCATION.

3-33

ODT COMMAND SEQUENCES AND FUNCTIONS
Typing the backslash command when a byte location is currently open
causes ODT to reprint the contents of the byte location;
as shown
below:
_0,23\021 \021

iREPRINTS VALUE OF BYTE LOCATION.

Typing the backslash command when a location is not open causes ODT to
print the byte value of the last-opened location, as shown below:
_0,234/000247 123456 <CR)
_\056
iPRINTS LOW-ORDER BYTE OF
iPREVIOUSLY-OPENED WORD LOCATION.
_0,237\041 <CR)
_\041

3.14.2

iREPRINTS VALUE OF PREVIOUSLY;OPENED BYTE LOCATION.

Print Byte Mode ASCII Character:

or a l

Typing the single-quote character
(I)
when a word location is
currently open causes ODT to interpret and print the low-order byte of
the location as one ASCII character, as shown below:
_0,232/034567 IW

iPRINTS THE CONTENTS OF THE OPEN WORD
iLOCATION AS ONE ASCII CHARACTER.

Typing the single-quote character when a byte location is open causes
ODT to interpret and print the byte value as one ASCII character, as
shown in the examples below:
_0,232\167 IW
_0,1020\323 'S
_0,233\071 19
When the single-quote character is preceded by an address expression,
ODT uses the expression as an argument in determening the location to
be interpreted and printed, as shown below:
_0,232 1 W

iINTERPRETS REFERENCED LOCATION AS
iONE ASCII CHARACTER.

If no location is currently open when the single-quote command is
issued, the previously-opened location is interpreted and printed, as
shown in the following sequence:
_0,232/034567 <CR)
_IW

3.14.3

iINTERPRETS PREVIOUSLY-OPENED WORD
iLOCATION AS ONE ASCII CHARACTER.

Print Word Mode ASCII Characters:

"or a"

Typing the double-quote character
(")
when a word location is
currently open causes ODT to interpret and print the contents of the
location as two ASCII characters, as indicated below:
_0,232/034567 "W9

iPRINTS THE CONTENTS OF THE OPEN WORD
iLOCATION AS TWO ASCII CHARACTERS.

3-34

ODT COMMAND SEQUENCES AND FUNCTIONS
If the double-quote character is preceded by an address expression,
ODT takes the expression as an argument in determining the location to
be interpreted and printed, as shown below:
_0,232"W9

iINTERPRETS REFERENCED LOCATION AS
iTWO ASCII CHARACTERS.

If no location is currently-open when the double-quote command is
issued, the previously-opened location is interpreted and printed, as
reflected below:
_0,232/034567 <CR>
_"W9

iINTERPRETS PREVIOUSLY-OPENED WORD
iLOCATION AS TWO ASCII CHARACTERS.

Note that the double-quote command is effective only when issued in
connection with task locations which fallon even (word-boundary)
addresses, as shown below:
_0,232/034567 W9 <CR>
_0,232\167 "W9 <CR>

iINTERPRETS ENTIRE WORD VALUE.
iALSO INTERPRETS ENTIRE WORD.

In contrast, however, issuing the double-quote command in connection
with an odd address (byte) location, although legal, merely causes the
3-digit octal byte value to be reprinted, as reflected in the
following sequence:
_0,233\071 "071 <LF)
0,000234 \346 "F <LF>
0,000235 \025 "025

iREPRINTS ODO BYTE VALUE.
iINTERPRETS WORD LOCATION NORMALLY.
iREPRINTS ODO BYTE VALUE.

Note, in the second line above, that the word location relocatable 234
is interpreted normally in its entirety, even though the location is
currently open in byte mode. This example underscores the usefulness
of the double-quote character only in connection with word-boundary
locations.

3.14.4

Print Word Mode Radix-50 Characters:

% or a%

Typing the percent sign (%) when a word location is open causes ODT to
interpret and print the contents of the location as three Radix-50
characters, as shown below:
_0,232/034567 %IGI

iPRINTS THE CONTENTS OF THE OPEN WORD
iLOCATION AS THREE RADIX-50
iCHARACTERS.

If the percent sign is preceded by an address expression
(a), ODT
evaluates the expression to determine the location to be interpreted
and printed, as shown below:
_0,232%IGI

iINTERPRETS REFERENCED LOCATION AS
iTHREE RADIX-50 CHARACTERS.

As with the preceding single-quote and double-quote interpretive
commands, typing the percent sign when no location is currently open
causes ODT to print the contents of the previously-opened location in
Radix-50 form, as shown below:
_0,232/034567 <CR)
_%IGl

iINTERPRETS PREVIOUSLY-OPENED
iLOCATION AS THREE RADIX-50
iCHARACTERS.
3-35

ODT COMMAND SEQUENCES AND FUNCTIONS
Also, the percent sign is effective only when issued in connection
with an even address location, even though a word-boundary location
may be currently open in byte mode, as shown below:
_0,242/001542 % UZ (CR)
_0,242\142 % UZ (CR)

iINTERPRETS ENTIRE WORD VALUE.
iALSO INTERPRETS ENTIRE WORD.

Using the percent sign in connection with an odd address value has the
same effect as that described above for the double-quote character, as
indicated below:
_0,241\025 %025 (LF)
0,000242 \142 % UZ (LF)
0,000243 \003 %003

3.15

iREPRINTS ODD BYTE VALUE.
iINTERPRETS WORD LOCATION NORMALLY.
iREPRINTS ODD BYTE VALUE.

INTERPRETING EXPRESSION VALUES:

The equal sign (=) enables the user to interpret exp~ession values,
address values, and a variety of other expression forms involving
arithmetic operations. The use of this command implies that it is
preceded by the entry of one or more characters constituting a legal
ODT expression.
This command cannot be used to interpret the currently-open location
or the last previously-opened location. A character sequence must be
entered overtly prior to issuing the = commandi otherwise, ODT prints
out a string of six octal zeros (000000).
As shown in the examples below, this command causes any expression
value which precedes it to be converted to a 6-digit octal value.
In
addition, the word so printed is stored in the quantity register
(see
$Q, Table 3-1).
A wide range of operations is possible using this
command, as reflected in the following sequences:
_0,370iR

_0,0=000370
_2,16*$00+6=003364
_0,16=000406
_370+16=000406
_0,16+16+2=000426
_370+16+16+2=000426
_16+370=000406
_16-370=177426
_-370+16=177426
_-370-16=177372
_-177777+16+16=000035
_+1+16+16=000035
_177777+16+16=000033
_-1+16+16=000033
_232323=032323
Note in the sequence above that any expression value that references
relocation register 0 causes ODT to take the current contents of that
register as an argument in evaluating the
expression.
Those
expressions beginning with 0, cause the value 370(8) to be used as the
effective value of that element, as established through the initial
command of the sequence above. Any of the relocation registers can be
used in this manner.
Both positive and negative values may be specified as arguments in an
expression, as reflected throughout the examples above. ODT performs

3-36

ODT COMMAND SEQUENCES AND FUNCTIONS
the necessary arithmetic calculations and prints out the result
6-digit octal value.

Note also that any expression value preceding the equal sign is
truncated to 16 bite before being evaluated and printed in 6-digit
octal form, as shown in the last expression in the above sequence.

3.16

USING SPECIAL ARGUMENTS IN.ODT COMMANDS

The special arguments described below may be
elements a and k in ODT commands.

3.16.1

used

place

the

Current Location Indicator:

When used in a command sequence, the dot (.) represents the address of
the currently-open location, as shown below:
_1000/000000 .=001000

3.16.2

(.) REFERENCES ADDRESS OF
iLAST OPENED LOCATION.

iDOT

Constant Register Indicator:

The user may store any l6-bit expression value in the constant
register
(see $C, Table 3-1).
To open the register and print its
contents, the user issues the $C/ command. Any new value desired can
then be entered directly, followed by a <CR) command. The value so
contained in the constant register may then be used in any subsequent
ODT operations by typing the letter C as an argument in a command.
The example below shows how the
modified:
_$C/OOOOOO 123 <CR)

constant

accessed

and

iCONSTANT REGISTER OPENED, MODIFIED
iTO CONTAIN 123, FOLLOWED BY RETURN

_/000123

3.16.3

iCOMMAND.
iCONSTANT REGISTER OPENED, CURRENT
iCONTENTS ARE PRINTED.

Quantity Register Indicator:

Each time ODT prints a value on the console, the value is stored in
the quantity register
(see $Q, Table 3-1). The value so stored may
then be used in any subsequent ODT operations by typing Q as an
element of a command.
This facility is useful in modifying open
locations. For example, if location 1342 contains a value which is
too small for current debugging purposes, the value may be modified,
as shown in the first line of the command sequence below:
_1342/173214 Q+10 <CR)
_/173224

THE VALUE 10 TO THE CURRENT
iCONTENTS OF LOCATION 1342.
iSLASH OPENS PREVIOUS LOCATION,
iPRINTS ITS CONTENTS, AND STORES NEW
iVALUE IN Q REGISTER.
iADD

Therefore, when Q is employed as an argument in an expression in this
manner,
the contents of the currently-open location are modified to

3-37

ODT COMMAND SEQUENCES AND FUNCTIONS
contain the octal equivalent of the expression. Note in the last line
of the sequence above that issuing the slash command verifies the
modification of the previously-open location.
As a second example, assume that the contents of user general register
3 point to a routine that has been relocated through relocation
register 5. The following command sequence might then occur:

_$3/013624 Qj5R

iSETS RELOCATION REGISTER 5 TO 013624
i (THE CURRENT VALUE OF Q REGISTER).
iEVALUATES THE RELOCATABLE ADDRESS
iEXPRESSION, PRINTS THE VALUE OF THE
iEXPRESSION, AND STORES THIS WORD IN
iTHE QUANTITY REGISTER.

_5,20=013644

After the relocatable address expression in the example above is
evaluated,
the quantity register contains the value 013644(8), while
relocation register 5 retains the value 013624(8) set in the preceding
command.

3.16.4

Radix-50 Operator:

The asterisk (*) is an arithmetic operator that is used primarily in
the calculation of Radix-50 arguments. Calculating such arguments is
necessary if the user wants to enter any of the Radix-50 characters
into a word location. The asterisk (*) allows the user to derive the
6-digit octal equivalent of the desired Radix-50 character(s) so that
the proper value can be entered into the appropriate location. Table
3-2 lists all the legal Radix-50 characters,
together with an
equivalent numeric value that is used in conjunction with the asterisk
to calculate a 6-digit octal representation of any combination of up
to three Radix-50 characters.
By consulting Table 3-2, the u~er can calculate any desired 1- to
3-character Radix-50 sequence for entry into a word location. For
example, if it is desirable to enter the Radix-50 characters ABC into
a given location, the 6-digit octal representation of these characters
is calculated as follows:
_1*2*3=003223
Note from this sequence that the numeric values 1, 2, and 3 are taken
from Table 3-2 as the arguments to be used in the calculation. For
this purpose, these numeric values represent the Radix-50 characters
A, B, and C.
Hence, the 6-digit result of this calculation is the
octal value that must be entered into the desired location to
correctly represent the intended Radix-50 sequence.
Table 3-2 may be used in this manner to calculate any corresponding
6-digit octal value of any desired combination of three Radix-50
characters, including the special characters space, $, and dot (.).
The following sequences illustrate how the Radix-50 operator
be used:
_1052/174777 %999 1*2*3=003223 3223 <CR)
_%ABC
_1054/003151 %AAA 1*3*5=003275 3275 <CR)
_%ACE

3-38

(*)

may

aDT COMMAND SEQUENCES AND FUNCTIONS
In the examples above, note that the contents of the open location are
first interpreted by typing the percent sign (%). This command,
although entirely optional, permits the user to ascertain the current
contents of the location in Radix-50 form (see Section 3.14.4). At
this point, if the· user elects to enter some other Radix-50 character
sequence, he may do so by calculating its value as shown above and
then entering this value before closing the location.
Also optional
is the second line of each sequence which interprets the new Radix-50
character(s) in the changed location to verify their accuracy.
As a further example, the user may wish to enter the Radix-50
characters $TJ into location 1054. After opening this location, Table
3-2 is consulted for the corresponding numeric values to be used in
the calculation.
These values are determined to be 33, 24, and 12.
The sequence of OOT operations then proceeds as follows:
_1054/124157 33*24*12=125752 125752 (CR)
_%$TJ
Note that spaces (blanks) are valid characters in deriving Radix-50
character sequences. A space is represented in the calculation as 0,
as shown below:
_1*0=000050
_0*1=000001
_2*0*3=006203
Table 3-2
Legal Radix-50 Characters and Numeric Equivalents
Radix-50
Character

Numeric
Equivalent

Radix-50
Character

Numeric
Equivalent

Space
A

0
1
2
3
4
5
6
7
10
11
12
13
14
15
16
17
20
21
22
23

24
25
26
27
30
31
32
33
34
35
36
37
40
41
42
43
44
45
46
47

C
0

E
F
G
H
I

J
K

L
M

N
0
p
Q
R

U
V
W

X
y
Z

Unused
0
1
2
3
4
5
6
7
8
9

3-39

CHAPTER 4
ERROR DETECTION

4.1

COMMAND

~NPUT

ERRORS

ODT checks the legality of an address when commanded to open a
location for examination or modification.
If an error is detected,
ODT responds by printing the question mark (?) character, followed by
the underline ( ) prompting character on the next line.
For example,
if the command:

177774/ ?
references nonexistent memory or an address outside the task's
partition, the request is ignored, and the appropriate typeouts occur.
In addition, a command such as:
$20/ ?
which specifies an invalid (nonexistent) register, causes ODT to flag
the line with a question mark (?), ignore the request, and print the
prompting character.
In general, typing an illegal character or command causes
ignore the input, print the question mark error indicator

ODT

and wait for a valid command.
To cause ODT to ignore a command just entered, any illegal character
(such as the decimal value 8 or 9) m~y be typed, causing the command
to be treated as an error (ignored).
ODT suspends task execution whenever a breakpoint location
is
encountered
(i.e., the user program traps to ODT's breakpoint
processing routine).
If the breakpoint routine is entered and no
known breakpoint has caused the trap action, ODT prints a message in
the form
BE:001542
and waits for another command.
In the example above,
the message
BE:001542 denotes a bad entry from location 001542 (see BE, Table
4-1). This type of error message may be caused by an illegal BPT
instruction ln the user
task, setting the T-bit in the Processor
Status Word ($S), or a branch to a location within ODT.

4-1

ERROR DETECTION
Although octal op code 000003
(the BPT instruction)
is a valid
instruction in a user program,
its use is discouraged, since this
instruction will result in an unwanted breakpoint when the program is
run under ODT control.

4.2

TASK IMAGE ERROR CODES

In addition to command input errors, ODT alerts the user to certain
hardware-detected errors that occur during task execution. Such
errors, which are attributable to problems in the task itself,
result
in a trap to one of the error-handling routines. ODT activates the
appropriate error-handling routine, which then evaluates the condition
and prints out an error code in the form:
cc:k
where cc represents one of the 2-character alphabetic error codes
listed in Table 4-1, and k represents the 6-digit octal address
following the location in error, unless the code is BE.
If the code
is BE, k represents the address of the location in error. The
alphabetic error code and the address value are always separated by a
colon (:).
At this point, the user can examine the error location,
register
values,
and other key locations in the task image. If the cause of
the error can be determined, appropriate modifications can then be
made in the user task and noted on the assembly listing;
if the error
cannot be isolated, it is advisable to load a fresh copy of the entire
task and initiate a new debugging session.
Table 4-1
ODT Error Codes
Code

Meaning

MP*

Memory protect violation or illegal memory reference.

Odd adhress reference on word instruction.

lOT instruction executed.

Reserved or illegal instruction executed.

Non-TRAX EMT instruction executed.

TRAP instruction executed.

T-bit exception. T-bit was set,
but setting was not
caused by a breakpoint, single-step mode, a Proceed
command, or a BPT instruction.
Probably caused by
improperly maintained task stack resulting in a word
(that happens to have its bit 4 set) being used as the
Processor Status Word (PS).

Floating-point instruction error.

Breakpoint instruction executed at unexpected location.

4-2

APPENDIX A
PROCESSOR STATUS WORD

The Processor Status Word (PS), stored at hardware location 777776,
contains information on the current status of the processor. The
information contained in this location includes the current and
previous operational modes of the processor (mapped system only), the
current processor priority, an indicator which, when set, causes a
trap upon completion of the current instruction, and condition codes
describing the results of the last instruction executed.
The format
of the Processor Status Word is shown in Figure A-I below.

CARRY
OVERFLOW
'------ ZERO
NEGATIVE
TRACE TRAP
' - - - - - - - - - - - - - - - - - - - - - GEN REG SET
~-----------------------PREVIOUS MODE
~---------------------------CURRENT MODE
L--._ _ _ _ _

L..-_ _ _ _ _ _

Figure A-I

A.l

Format of Processor Status Word

MODES (MEMORY MANAGEMENT OPTION)

Bits 15 and 14 of the Processor Status Word indicate the current
processor mode, i.e., either User mode (11) or kernel mode (00). Bits
13 and 12 indicate the previous mode, i.e, the mode the machine was in
(User or Kernel) prior to the last interrupt or trap.

A.2

PROCESSOR PRIORITY

The current priority of the central processor is maintained in bits 7
through 5 of the Processor Status Word.
The central processor
operates at anyone of eight levels of priority (0 through 7).
When
the central processor is operating at level 7 (the highest priority),
an external device cannot interrupt it with a request for service.
The central processor must be operating at a lower priority than the
external device's request in order for the interrupt to take effect.
The eight processor levels provide an effective interrupt mask.

A-l

PROCESSOR STATUS WORD
A.3

TRAP (T-BIT)

The trap bit (bit 4) can be set or cleared under program control.
When set,
a processor trap will occur through location 14 upon
completion of the current user instruction, and a new Processor Status
Word will be loaded.
The trap
(T)
bit is especially useful in
debugging programs, since it provides an efficient means for
stepping
through the task one instruction at a time. ODT uses the T-bit to
execute instructions in the single-instruction mode (see Section 3.7).
4

A.4

CONDITION CODES

The condition codes N, Z, V, and C (bits 3 through 0,
contain
information indicating the result of the
processor operation. These bits are set as follows:
N=l,
Z=l,
V=l,
C=l,

A.S

respectively)
last central

if the result was negative.
if the result was zero.
if the operation resulted in an arithmetic oyerflow.
if the operation resulted in a carry from the
significant bit.

most

TRAP PROCESSING

Both interrupts and trap instructions automatiGally cause the previous
Processor Status Word and program counter to be saved on the stack and
replaced by the new values stored in the associated interrupt vectors.
The interrupt vectors contain a new program counter value and new
Processor Status Word. The user can cause the central processor to
switch modes automatically
(context switching), or disable the trap
bit whenever a trap or interrupt occurs.

A-2

APPENDIX B
SEARCH ALGORITHMS

As described in Section 3.8, ODT allows the user to search for
specific bit patterns in the task or to identify words in the task
which reference a specific location. The algorithms for
these two
types of search operations are described below.

B.l

WORD/BYTE SEARCHES

(W or N)

The word search compares selected bits in a range of memory words with
a user-specified search argument.
The bits to be compared in the
memory words and the search argument are defined through the search
mask register
(see Section 3.8.1).
If all the selected bits in any
given memory word and the search argument are equal, a match has
occurred, and ODT prints the "unmasked" task word.
The algorithm for the word search operation follows:

B.2

Fetch the memory word at the current address.

Perform the logical operation XOR
(exclusive
memory word and the specified search argument.

Perform the logical operation AND on the result from
and the specified mask.

If a W search is being performed and the result of Step 3 is
zero, or if an N search is being performed and the result of
Step 3 is nonzero, print the address of the unmasked word and
its contents.

Add two (2) to the current address, fetch the word in the
next location, and go to Step 2.
If, after adding 2 to the
current address, the resulting value is greater than that
contained in the high search limit register (see $H, Table
3-1), print the underline (_) prompting character and return
control to the ODT command decoder routine to await the next
user command.

OR)

the

Step

EFFECTIVE ADDRESS SEARCH (E)

In the effective address search, ODT treats every task word within the
specified search range as a value which has a possible direct
relationship to the search argument, i.e., as a word which addresses a
specified location.
Each address to be compared is first masked by
the contents of the search mask register (see $M, Table 3-1)
before
comparison.
Therefore,
the contents of the mask register should
normally be set to 177777 for the E command.
B-1

SEARCH ALGORITHMS
In the algorithm for the effective address search described below, the
following symbology is used:
(X)

The contents of location X.

The effective address search argument.

Fetch the word at location X (the current location).

If (X) = K, i.e., if location X contains a value which is an
absolute address reference to the search agrument (i.e.,
contains the search argument itself), print the contents of
location X and go to Step 5.

If (X)+X+2
K, i.e., if the contents of location X, as
indexed by the contents of the program counter (PC), are
equal to the search argument, print the contents of location
X and go to Step 5.

If low-order (X)x2+X+2 = K, i.e.,
if the contents of the
low-order byte at location X reference a location whose
address value is the same as the search argument, print the
contents of location X, and go to Step 5.

Add 2 to the current address.
If the resulting value is
greater than that contained in the high search limit register
(see $H, Table 3-1), print the underline
(_)
prompting
character and return control to the aDT command decoder
routine to await the next user command;
otherwise, go to
Step 1.

B-2

INDEX

Access mode, specifying an, 9-28
AID, 7-14
Allocation XAB, 7-17
ALN, 7-20
ALQ, 5-6, 7-21
AOP, 7-21
BID, 5-7, 6-3
BKS, 5-7
BKT, 6-3
BKZ, 7-22
BLN, 5-9, 6-3
BLS, 5-9
Bucket size, 5-7 to 5-9, 7-22

Calling sequence, RMS-ll, 9-3
CDT, 7-3
$CLOSE, 9-11
COD, 7-2
$ COMPARE , 4-2
Completion routines, 9-3 to 9-5
Completion status code, 5-24,
6-13, 9-6
$ CONNECT , 2-7, 9-13, 9-17
Context of record operations,
9-15
Control block fields,
accessing at runtime, 4-1 to
4-5
numeric values in 2-word, 4-2
offsets of, 4-2
usage, 9-5
Control blocks, user,
accessing fields in, 4-1 to
4-8
function of, 2-3
FAB, 2-4
NAM, 2-5
RAB, 2-4
XAB, 2-4
$CREATE, 9-7
CTX, 5-9, 6-4
Current context of record
operations, 9-15
Current Record, 9-15, 9-16

7-5
Date and Time XAB, 7-3
Declaring RMS-ll facilities,
$INIT, 3-4
$ INITIF, 3-4
.MCALL directive, 3-1, 3-2
ORG$, 3-3, 3-4

DAN,

$DELETE, 9-16, 9-18, 9-19, 9-30
DEQ, 5-10, 7-23
DEV, 5-11
Device characteristics, 5-11
DFL, 7-6
$DISCONNECT, 9-14
$DISPLAY, 9-10
DNA, 5-11
DNS, 5-12
ER$RTB, 9-16, 9-17, 9-20
ESA, 8-2
ESL, 8-3
ESS, 8-3
Extended Attribute Blocks,
allocating, 7-1, 7-2
Allocation, 7-17
Date and Time, 7-3
existing files and, 2-6
file operations and, 2-5
File Protection Specification,
7-15
Key Definition, 7-4
linking, 7-2
new files and, 2-6
order of, 7-2
Sununary, 7-25
types of, 7-1

F$ALQ, 5-6, 5-7
F$BKS, 5-9
F$CTX, 5-9
F$DEQ, 5-10
F$DNA, 5-12
F$DNS, 5-12
F$FAC, 5-13
F$FNA, 5-14
F$FNS, 5-15
F$FOP, 5-16
F$FSZ, 5-17
F$LCH, 5-17
F$MRN, 5-18
F$MRS, 5-19
F$NAM, 5-20
F$ORG, 5-21
F$RAT, 5-21
F$RFM, 5-22
F$RTV, 5-23
F$SHR, 5-23
F$XAB, 5-24
FAB (the RAB field), 6-5
FAB (File Access Block),
allocating a, 5-4
fields in a, 5-5
Index-l

INDEX (Cont.)

FAB (Cont.) I
file operations and the, 2-5
function of a, 2-4
FAB$B, 5-4
FAB$E, 5-4
FAC, 5-13
$FETCH, 4-3
Fields, control block,
accessing at runtime, 4-1 to
4-5
numeric values in 2-word, 4-2
offsets of, 4-2
usage, 9-5
File Access Block,
allocating a, 5-4
fields in a, 5-5
file operations and the, 2-5
function of a, 2-4
File operations, 2-5, 9-6 to
9-12
File processing macros, 2-2,
9-2, 9-6 to 9-12
$FIND, 9-17, 9-19, 9-21 to 9-23
Fixed control area size, 5-17
Fixed format records, 5-19,
5-22
FLG, 7-6
FNA, 5-14
FNS, 5-15
FOP, 5-16
FSZ, 5-17

$GET, 9-23 to 9-25, 9-27, 9-30

IAN, 7-9
IFI, 5-17
IFL, 7-10
Indexed file organization,
$FIND and the, 9-23
$GET and the, 9-25
$PUT and the, 9-27
specifying, 5-21
$UPDATE and, 9-29
$INIT, 3-4
$INITIF, 3-4
lSI, 6-5

KBF, 6-5
Key characteristics, 7-6
Key Definition XAB, 7-4
KNM, 7-10
KRF, 6-6
KSZ, 6-7

LAN, 7-11
LCH, 5-17
LOC, 7-24

MEC, 6-8
.MCALL directive, 3-1, 3-2
Move mode, 9-19
MRN, 5-18
MRS, 5-19

N$ESA, 8-2
N$ESS, 8-3
NAM (the FAB field), 5-20
NAM (Name Block),
allocating a, 8-1
fields in a, 8-2
function of a, 2-5, 2-6
Name Block,
allocating a, 8-1
fields in a, 8-2
function of a, 2-5, 2-6
Next Record, 9-15, 9-17
NUL, 7-11
NXT, 7-2, 7-3

$OFF, 4-5
$OPEN, 9- 8
Options,
file processing, 5-16
record processing, 6-11
ORG$, 3-3, 3-4
ORG, 5-20, 5-21
Organization, specifying file,
5-20, 5-21

Placement control, 7-19 to 7-25
POS, 4-3, 4-4, 4-6, 4-7, 7-12
PRG, 7-15, 7-16
PRJ, 7-16
PRO, 7-16, 7-17
Protection Specification XAB,
7-15
Protection word format, 7-16
$PUT, 9-17, 9-18, 9-19, 9-20,
9-21, 9-25 to 9-28

R$BKT,
R$CTX,
R$FAB,
R$KBF,

Index-2

6-3
6-4
6-4
6-5

INDEX (Cont.)

R$KRF, 6-6
R$KSZ, 6-7
R$MBC, 6-8
R$RAC, 6-9
R$RBF, 6-10
R$RHB, 6-11
R$ROP, 6-11
R$RSZ, 6-12
R$UBF, 6-14
R$USZ, 6-14
RAB (Record Access Block),
allocating a, 5-4
fields in a, 6-2
function of a, 2-4
record operations and the, 2-6
RAB$B, 6-1
RAB$E, 6-1
RAC, 6-9, 9-18
Radix,
of assembly-time initialization macros, 5-2
of run tine field access macros,
4-2
Random access mode, 2-8, 9-18
RAT, 5-21
RBF, 6-9, 9-29
RDT, 7-3
Record Access Block,
allocating a, 5-4
fields in a, 6-2
function of a, 2-4
record operations and the, 2-7
Record access modes, 2-7, 2-8,
9-18
Record access streams,
defined, 2-7
disconnecting, 9-13
establishing, 9-14
Record operations,
defined, 2-6
macros, 9-2, 9-12 to 9-30
Record processing macros, 9-2,
9-12 to 9-30
Record transfer mode, specifying, 9-19
Records,
specifying attributes of, 5-21
specifying format of, 5-22
specifying size of, 5-19
REF, 7-13
Relative file organization,
$FIND and the, 9-22
$GET and the, 9-25
$PUT and the, 9-25
specifying, 5-20
$UPDATE and the, 9-29
RFA (the RAB field), 6-10
RFA access mode, 2-8, 9-18
RFM, 5-22

RHB, 6-10
ROP, 6-11, 9-19
RSZ, 6-13, 9-19
RTV, 5-23
Runtime processing macros,
file, 2-2
record, 2-2
RVB, 7-14
RVN, 7-3

Sequential access mode, 2-7,
9-18
Sequential file organization,
$FIND and the, 9-22
$GET and the, 9-25
$PUT and the, 9-27
specifying, 5-21
$UPDATE and the, 9-29
SIZ, 4-4, 4-6, 4-7, 7-14
$ STORE , 4-6
Stream record format, 5-19, 5-22
STS, 5-24, 6-13, 9-6
STV, 5-24, 6-13, 9-6
Summary XAB, 7-25

$TESTBITS, 4-7
$ TRUNCATE , 9-16, 9-17

UBF, 6-14, 9-20
$ UPDATE , 9-17, 9-18, 9-19,
9-21, 9-28 to 9-30
User control blocks,
accessing fields in, 4-1 to 4-8
function of, 2-3
FAB, 2-4
NAM, 2-5
RAB, 2-4
XAB, 2-4
USZ, 6-14, 9-20

Variable format records, 5-19,
5-22
VFC format records, 5-17, 5-19,
5-23, 6-10
VOL, 7-25

X$AID, 7-19
X$ALN, 7-20
X$ALQ, 7-21

Index-3

INDEX (Cont.)

X$AOP,
X$BKZ,
X$DAN,
X$DEQ,
X$DFL,
X$FLG,
X$IAN,
X$IFL,
X$KNM,
X$LAN,
X$LOC,
X$NUL,
X$NXT,
X$POS,
X$PRG,
X$PRJ,
X$PRO,
X$REF,

7-21
7-22
7-5
7-23
7-6
7-6
7-8
7-9
7-10
7-11
7-24
7-11
7-3
7-12
7-15
7-16
7-16
7-13

X$SIZ, 7-14
XAB (the FAB field), 5-24
XAB (Extended Attribute Block),
allocating, 7-1, 7-2
Allocation, 7-17
Date and Time, 7-3
existing files and, 2-6
file operations and, 2-5, 2-6
File Protection Specification,
7-15
Key Definition, 7-4
linking, 7-2
new files and, 2-6
order of, 7-2
Summary, 7-25
types of, 7-1
XAB$B, 7-1
XAB$E, 7-2

Index-4

TRAX ODT
Reference Manual
AA-D343A-TC

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