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Basic6809 user guide
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Use this patch program to downgrade your BASIC V module to understand 6809
assembler.

Only really useful (and then literally) if you (still) develop sizable 6809
assembler programs. Monolithic sources of whatever size possible, no more
splitting up and other complications due to the target machine's tiny memory.
All of BASIC V's facilities at your fingertips. Life is good.

Basic6809 takes a BASIC V module. And spits out a patched version of it that
understands 6809 assembler. It's that simple.

Three sources:

1) Your local RISC OS ROM
2) A RISC OS ROM image in a file
3) A BASIC module image in a file

Supported versions of BASIC V: 1.05, 1.16, 1.19, 1.20 (2 variations thereof),
1.28, 1.29.

Simply run Basic6809 with your source on the ready. If option 1 doesn't work,
try it 'before !Boot' (since the BASIC you run may have been patched or
replaced beyond recognition by the !Boot sequence).

To use a patched BASIC V module, simply *RMRun it when needed. It has a
different name than the old module, so it can safely be run alongside it.

The instruction syntax mostly matches the one presented in the Hitachi 6809
datasheets. Note the following features, exceptions and caveats:

- Any hex values are, of course, introduced with '&', not '$'.
- There are no '6809' directives, only the old 'ARM' ones, and they have their
  usual meaning (but OPT, of course, does not support ARM specific bits, and,
  for convenience, the DC directives (DCB, DCW, DCD) have been changed to
  encode big-endian values).
- 'Direct addressing' is not automatic, it must be forced. See next remark.
- Put a '<' or '>' before the instruction argument to force 8-bit or 16-bit
  versions of instructions, respectively. This applies to 'n,R' and 'n,PCR'
  addressing, and forces the choice between 'Direct' and 'Extended' addressing.

Assembler errors that can be generated:
  ERR 4, instruction not supported for OPT setting
  ERR 3, indexed instruction syntax error
  ERR 2, immediate value too big for instruction
  ERR 1, relative destination out of range

Updates of Basic6809 (if any appear) will be made available by (in order of
preference):

- World Wide Web : visit web.inter.nl.net/users/J.Kortink
- Electronic mail : email kortink@inter.nl.net

Enjoy !


John Kortink