[Coco] Assembler modifications and a super 6309 processor

Darren A mechacoco at gmail.com
Tue Sep 8 15:42:38 EDT 2009

On 9/8/09, jdaggett at gate.net  wrote:
> Another Questionfor the Software Guru's out there:
> <snip>
> Adding the Immediate Mode for instructions like SBC, AND, EOR, OR and ADC
> for the
> the E,  F, and W registers is rather easy. Would it be worth the effort to
> undertake this? I
> can put all those all on page three of the opcode map and they would have
> the same
> opcodes as their page one instructions. The $11 page code would just switch
> target
> register acted on. Real simple to do.


Looking at the opcode map, I think you would want to use the $10 page
code for instructions using W (and use the same base opcode as the
instructions for B).  The 6309 variants for D already share the same
base opcode as A.

If you add new instructions, could you also add a new bit to the MD
register to enable/disable those instructions?  Some existing 6309
software may expect certain opcodes to trigger an Illegal Instruction


More information about the Coco mailing list