A simple (and simple minded) assembler for the Motorola 6809.
(updated Dec 2022).
A refreshed readme to replace the "place holder", but probably still insufficient.
Excerpts from the earlier document:
This is a relatively simple minded, simple assembler for the Motorola 6809 written as a single C source file accepting a fairly broad set of assembler directives accepting the main code related directives from the early Motorola code through to more recently accepted common directives.
It only accepts the Motorola 6809 op-codes, though with modest work I would expect it would be easily extended to cover the Hitachi 6309 derivatives.
Speed was not a design criteria, so the program executes at least three passes of the source code to ensure that all labels have "stabilised" on a set value, the last pass generating the output.
Some basic testing has been undertaken against a version of the "assist09.asm" source code originally published by Motorola and comparing the output of this against both the published output and that generated by another '09 assembler. As this software currently stands it seems to produce the same resulting code as Motorola expected, and differences with the other assembler used can be tracked down to different interpretations of operator precedence and character constant handling.
December 2022 revisions:
The assembler has been "tweaked" to (optionally) accept original Motorola formatted source code as an alternative to a more modern syntax. This is not a change in any op-codes or arguments but relates to handling of the following elements:
- Labels starting in column 1 do not need terminate with a colon.
- The period symbol is now valid within a label.
- Character constants are preceded by only a single quote (').
- String constants are delimited by the slash character (/).
Some legacy operators are not implemented, yet. The cause of this is that, so far, I've not pinned down what they are (e.g. the '=' prefix operator; means "top byte of 16 bit word?")
Enabling 'legacy syntax' also enables a few possible warnings relating to potential clashes between the default syntax interpretation against the legacy version.
This may not be enough to assemble every original assembler file (or even most), but should assist in doing so.
Finally, the command line options accepted by the program (as displayed by '--help'):
Usage: asm68c9 [ {options} ] {filename}
Options:-
--hexadecimal Output text hexadecimal values
--intel Output Intel Hex format data
--motorola Output Motorola S records
--listing Output an assembly listing
--no-output Do not output any code
--stdout Send output to console
--legacy-syntax Accept legacy Motorola syntax
--symbols Output Symbol table
--dump-opcodes Display op-codes table
--help Display this help information
--debug Enable additonal debugging output
Jeff
Addendum/
This is starting to feel like it is almost useful. Useful enough to require a manual page of some sort? May be.
I have not yet started the actual project that was the cause for starting this software (building an mc6809 SBC), but once that is under way then I am sure that the test of actual use will force out more wrinkles in the assembler.
Extra Addendum/
I really should add support for the Hitachi 6309 processor. It cannot be that difficult, surely.