ARM ASSEMBLER

In front, an ARM610 (33MHz) processor and support circuitry on a RiscPC processor card.
The RiscPC can accept two processors, the card behind the ARM being an Intel 486SXL-40
also clocked at 33MHz. Note the incredible size difference between the two processors.

On the left, an ARM710 processor card with a British 10 pence coin to give you an idea of size.
On the right, the original series 80486 co-processor.
It gets rather hot, but not hot enough to require a heatsink or fan.
The ARM, on the other hand, gets most of its heat simply by being near the 486!
The other big chip on the co-processor card is the ASIC, a device to munge the 80486 I/O into
something that can interface with the ARM processor bus.

80x86 assembler for Pentium™, Celeron™ etc processors...

The documents here relate to the low-power high-performance ARM processors used in PDAs, mobile phones, laser printers, Gameboy Advance, and of course the RISC OS computer range (formerly made by Acorn Computers, Cambridge, UK).
A lot of the detail relates to programming the ARM within the RISC OS environment, but it should also serve as a general resource for those programming the ARM under any system. Please note, however, that the 'Thumb' instruction set is not (yet) described.

IMPORTANT NOTE

There is no coverage for AArch64, at all.
It's an entirely different thing, and frankly loses a lot of what made the ARM great... but then these days people don't write assembler, compilers do...

Introduction

• Rationale

• News
    There are no 'new!' markers here,
    so be sure to read this to see what's new.

• Sanity warning

• Funnies

• A quick note on the notation used

• Your starter kit

• An introduction to assembler

The instruction set

• Instruction Quick Finder - lists all ARM instructions I'm aware of

• Instruction Quick Finder - a shorter version, for typical RISC OS coding

• Registers and processor modes

• The Processor Status Register and conditional execution

• Shifting

• SWIs

• Pseudo-instructions

• Branch instructions

• Arithmetic and Logical instructions

• Multiplication instructions

• Comparison instructions

• Register Load and Store instructions

The ARM processor

• Where the ARM came from

• Where might you find an ARM?

• RISC vs CISC

• ARM processor types, and differences

• The pipeline

• The stack

• Memory Management

• Memory Schemes and Multitasking

• Processor setup via co-processor 15
  and about co-processors

The BASIC assembler

• Writing assembler in BASIC

• OPT settings

• CALL and USR (in BASIC)

• Special facilities available from BASIC

• Converting BASIC to assembler

• The debugger

Relocatable Modules

• Introduction to module code

Useful hints

• Tips and Tricks

• Hints for programming

APCS

• What is APCS?

• Opinions on various DDE assemblers

• Basic introduction to writing APCS code

• Using the DDE but not using APCS...

• Useful objasm macros

32-bit operation

• A brief look at 32 bit ARM - the next generation of ARM processors

• Basic rules for writing 32-bit safe code
  See also:
  • The Processor Status Register; 32 bit usage

Mathematics co-processor

• Floating Point Unit - a brief overview
    Provided for completeness.

Hardware

• Interfacing with hardware
    Podules, and the FDC37C665.

Hackery

• Speeding up the TaskWindow

• An even better TaskWindow

• How to unsqueeze an application

Can't find what you're after?

Examples

• Example 1: Screen image compressor

• Example 2: Screen image loader

• Example 3: A better compressor and a multi-format loader

• Example 4: Resetter module
  ...including how to write a simple relocatable module.

• Example 5: Mouse position display
  ...Example of APCS assembler.
     (requires objasm v2.00 and link v4.00 (or later))

• Example 6: Mode 21 -> 28 converter
  ...Example of interworking APCS assembler and C.
     (requires objasm v2.00, link v4.00, and cc v4.00 (or later))

• Example 7: DiscAccess (and DiscAccess Revisited)
  ...Fakes a blinking harddisc activity indicator.
     Example of vector claiming and callbacks, in a module.
     (revisited - an example of how to optimise)

• Example 8: Rebound
  ...A game!
     Demonstrates a stand-alone program, and floating point maths.

• Example 9: lowercase()
  ...Rewriting a commonly-used C function.
     More interworking assembler and C.
     (requires objasm v2.00, link v4.00, and cc v4.00 (or later))
  See also:
  • Don't be over zealous!

• Example 9b: lowercase() ... again!
  ...some rather interesting time-experiments.
     (requires the 26/32 compiler and assembler tools (can be easily modified))

• Example 101: Webite
  ...what better example than a web browser!
     (well, sources for RISC OS would be nice - but... I'm sure!)

Opinion

• Why bother? Acorn is dead!

• The Next Best Thing

• A call for code - and also I have released some of my own old source

• Don't be over zealous!

• Copyright and copying

• On being a programmer

Newsflash!

• My new computer!
  I bought a programmer's RiscPC from CJE Micro's RISC OS Programmer's Initiative. This is what I thought (in January 2001).

Links

• Links

• The Bush Internet box IBX-100
  As the Bush box information is in /assembler/resources/, this lead some people to figure that this is part of my assembler section. It isn't actually... But here's a link in case you came here looking for it.
  The reason why the pages are in with the assembler stuff is long and tedious. Don't ask.

If the downloads don't work...

• Help! Clicking the BASIC file link doesn't work!

Archives

• Download all of the example source (Zip deflate archive; 271K)
  Last update 2004/03/10

• Download code to call FP functions from BASIC
  By Peter Burwood, Public Domain; Zip deflate archive, 4K

• Download the APCS compiler test examples (Zip deflate archive; 4K)

• Download SparkPlug v2.25 (84K) (by David Pilling)
  To use this software:
  1. Set the filetype of the downloaded file to BASIC (&FFB), if it is not already.
  2. Change the current directory to where you would like SparkPlug to be written to. You can skip this step if it is fine to temporarily write to the root of the currently chosen drive.
  3. Double-click on the file to begin extraction.
  A suggested alternative is to copy the splug/basic application into RAMdisc, type *RAM (to select RAMdisc), then decompress to there, and finally to drag the decompressed application to where you'd like it to be. You'll need a RAMdisc of at least 208K.

And finally...

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