SSASM Users Manual-mc68000_eng.pdf

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M68000 Assembler

SSASM Users Manual

Version 1.032

August, 1993

Applix 1616 microcomputer project

Applix pty ltd

SSASM Users Manual

M68000 Assembler

Applix 1616 project

Even though Applix has tested the software and reviewed the documentation, Applix makes no

warranty or representation, either express or implied, with respect to software, its quality,

performance, merchantability, or fitness for a particular purpose. As a result this software is

sold "as is," and you the purchaser are assuming the entire risk as to its quality and performance.

In no event will Applix be liable for direct, indirect, special, incidental, or consequential damages

resulting from any defect in the software or its documentation.

The original version of this manual was written by Andrew Morton, based on David Farb’s

68000 assembler.

Additional introductory and tutorial material by Eric Lindsay

Editorial and design consultant: Jean Hollis Weber

Comments about this manual or the software it describes should be sent to:

Applix Pty Limited

Lot 1, Kent Street,

Yerrinbool, 2575

N.S.W. Australia

(048) 839 372

Private BBS systems (ringback) on (02) 554 3114 and (02) 540 3595

Revised material

ISBN 0 947341 ?? ?

MC68000®™ is a trademark of Motorola Inc.

Introduction

SSASM

is an assembler for the Motorola 68000 series of 16/32 bit microprocessors. It accepts

a file containing standard Motorola assembler mnemonics and directly produces executable

transient programs. That is, it produces

.exec

files for the Applix 1616.

SSASM

executes as either a built-in command, or as a normal transient program, under the 1616/OS

operating system on an Applix 1616 computer system. Versions of 1616/OS later than 3.2b

have

SSASM

, version 2.2, built into the operating system eproms. This is often very convenient,

because you can edit and assemble programs without using a disk drive, if you wish.

SSASM

supports all the instructions of the 68000 microprocessor, but does not support (at this

time) the special instructions for the 68010 and 68020. These opcodes may be implemented as

macro instructions. In addition,

SSASM

supports a variety of listing and pagination controls of

use when examining the list file, data declaration statements for initialising constants, file

inclusion and conditional assembly controls.

Two of the more interesting features of

SSASM

are

•

structured programming constructs (which don’t quite work)

•

macro processing capability (which do work)

The structured programming constructs should include

•

IF/THEN/ELSE

•

FOR/ENDF

•

WHILE/DO/ENDW

•

REPEAT/UNTIL

all of which would be very pleasant, if they worked correctly under all circumstances. However

you can easily get along without them, so don’t pay much attention to the chapter on how they

should work.

Macro processing permits conditional assembly inside macros, parameters to macros, automatic

generation of unique labels and other features, all detailed in the chapter on macros. Very handy

stuff, and essential once you get more familiar with the assembler.

1.1 References

The principle reference for the instructions on the 68000 is published by Prentice-Hall, Inc. of

Englewood Cliffs NJ, 07632, titled

M68000 16/32 Bit Microprocessor Programmer’s Reference

Manual,

written by the staff of Motorola. Prentice-Hall, about 200 pages. This lists all the

68000 instructions, and is an essential reference tool, but will not tell you how to use the

instructions, nor how to program in assembler. The current version is the fifth edition, and we

recommend not bothering with the first, second or third editions.

The

SSASM

manual does not duplicate the content of the

Reference Manual,

but should be used

in conjunction with it. The

Reference Manual

is available from Applix, and is recommended.

Other references which you may find helpful are the following:

Introduction

SSASM Assembler

1-1

The 68000: Principles and Programming,

by Leo J. Scanlon, published by Howard W. Sams,

238 pages. The 1981 edition is now somewhat dated, but still includes much excellent intro-

ductory material (and I picked it up cheap). Like most other assembler manuals, it assumes you

are familiar with the concept of assembler language, and merely want to add yet another version

to your repertoire. This is historically naive, since everyone has to start somewhere.

68000 Microprocessor Handbook,

by Gerry Kane, published by Wayne Green Books.

68000 Assembler Language Programming,

by Gerry Kane, published by Wayne Green Books.

I am not certain that Wayne Green Books are still available in Australia. A possible alternative,

by the same author, is below.

68000 Assembly Language Programming

by Gerry Kane, Doug Hawkins and Lance Leventhal,

published by Osborne McGraw-Hill, about 300 pages covering concepts, simple problems at

about the level of the Scanlon book, including over 50 program examples. Advanced topics

cover parameter passing, subroutines, I/O and interrupts, and there is a useful major coverage

of problem definition, program design, documentation, debugging and testing and so on. There

are also about 150 pages of appendix on the instruction set, a summary, and object code formats.

680x0 Programming by Example

by Stan Kelly-Bootle, published by Howard W. Sams, 482

pages. This one is a good introduction for those who have done minor work in another assembler.

It contains brief, but very clear, summaries of 680x0 differences, addressing modes, and

instructions, and then goes on to a number of commented code examples. The major example

is a 68000 version of the Kermit file transfer protocol, which is a fairly involved piece of work.

The beginner would be better served by the same author’s

68000, 68010, 68020 Primer

(but

since I don’t have a copy, I can’t review it).

68000 Assembly Language Techniques for Building Programs,

by Donald Krantz and James

Stanley, published by Addison-Wesley, 400 pages. After a brief overview of the 68000

instruction set (which contains some interesting viewpoints), this gets down to the main contents,

namely implementing a text editor in 68000 assembler. Lots of commented code, with expla-

nations of why things were done certain ways. While this is fine for the more experienced

assembler language programmer, the beginner may have problems coming to grips with such a

large project.

1.2 File Naming Conventions

SSASM

uses the following file naming conventions

filename.s

source file (must include

filename.exec

executable code.

filename.lst

listing output.

filename.xrel

relocatable code.

Although the source file must have a

extension, you should not type the

when invoking

the assembler, or the

makexrel.shell

program for making

.xrel

files.

SSASM

will automatically supply the

.exec

extension when it produces the final executable file,

by removing the

extension, and substituting the

.exec

extension. If you use the

-o

command

line switch, you will override this automatic

.exec

naming feature.

To produce standard Applix 1616 relocatable programs (the

.xrel

files), you actually run the

assembler twice, by using the

makexrel.shell

shell program that is explained later. This step

is usually only done when you have a complete working program, with all the bugs and problems

removed.

1-2

SSASM Assembler

Introduction

The listing file produced by the

-l

switch is an ASCII text file produced by the assembler. It

includes the text of your

source file, plus the expansion of any macros or include files, so

you can see what was actually in them. It also contains a hexadecimal representation of the

actual Motorola 68000 object code produced, and the location in memory they occupy. This

lets you see the actual code produced by the assembler. The listing switches or options such as

-f -h -t

let you alter the page length and appearance of the listing, to more easily suit it to

your printer or output device.

1.3 Invoking the Assembler

SSASM

is a command executed under 1616/OS. You invoke it by typing the name of the command,

followed by any switches (or parameters). For example

SSASM testcode

will assemble a file called

testcode.s

from the current directory.

The file

testcode.s

is a simple ASCII text file, usually produced using the

edit

inbuilt

command. It contains lines of text, each usually a single Motorola 68000 command. The details

of this are discussed in section 2.

Switches are specified by a leading dash

immediately followed by a letter (upper or lower

case), sometimes followed by a file name or other parameters. There must be at least one blank

between the switch and the file name, but no blanks between the switch and parameters (see

below).

The general form to invoke

SSASM

(where [ ] enclose optional switches) is

ssasm sourcefile [-flnprv] [-h pagelen] [-o objfile] [-t tabs]

The complete list of switches you may specify is

-f

use form feed between pages of the listing output.

-h[nn]

set listing page length to

lines in total.

-l

produces listing output, to standard output. The

-h -f

and

-t

options

vary the format of the listing file.

-n

no output of an executable file. Assemble only. Use to test your syntax,

and so on.

-o

[filename] specifies the object filename for output. The default output file’s name

now ends with

.exec

. The

-o

option overrides this. If no

-o

option is

specified, the object file’s name is that of the source file, with the

extension stripped off and

.exec

added.

-p

not working yet. Should produce an output ready for linking to a relo-

catable form directly, without needing to use

makexrel.shell

-t[nn]

set tab stops every

columns

-v

verbose mode, prints sign on message, version number and status infor-

mation as assembly proceeds.

Switches may be specified in any order, but file names must immediately follow their respective

switches. Switches and file names may be entered in any combination of upper and lower case.

All file names are translated to upper case for use by 1616/OS.

A sample command such as

-r

ssasm testcode -o objout -l

Introduction

SSASM Assembler

1-3

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