ARM Decoder Software - Useful for Compiler Writers

Many years ago I found some software by Henrik Bjerregarrd Pederson. The latest version I have is from July 1992.

This gives you 32-bits to click on to flip between zero and one and it tells you the ARM instruction that is executed by that 32-bit number. It uses the Debugger_Disassemble SWI to do this. This means it still works now, even for VFP instructions.

The problem is the icons are too small on a modern screen, the bits are not numbered. There is a lot more this software could do.

I’ve created a fresh new program to tackle the same problem.

Here are the improvements:

1) Bigger icons to click, for bigger screens
2) Numbered bits by a header row
3) Menu click to set each four-bit block to a hex value
4) Up to four bits can be set to a question mark with adjust. Multiple instructions will be shown, up to sixteen depending on the number of question marks you set. This allows you to compare what a group of bits are doing. As an example, try setting the four bits numbered 28 to 31 to a question mark with the adjust click and see all the conditions for the instruction. The instruction encodings are in hex to the left of each instruction.
5) Click on an instruction when a list appears to set the bits to that instruction, removing all the question marks in one click.
6) Menu click to open a window containing simple commands such as ADD or SUB, click on one to get a simple instruction of this type. Example, you can click on MUF to get a FPA/FPE multiply instruction. Basic ARM, FPA and very basic VFP is included.

This can be downloaded from:

http://www.ro32.co.uk/armenc.zip,a91

You may need to move this to a writable directory, set the file type of !Fix to Obey and run this to set the files types and filenames correctly.