[Coco] Assembler Question???

Darren A mechacoco at gmail.com
Wed Sep 2 13:11:27 EDT 2009

On 9/2/09, jdaggett at gate.net wrote:
>Also I seem to remember that is how the internal workings of the
> MC6809
> is. There is actually no subtractor but the assemly code has the 2's
> compliment of the
> subtrahend and does addition.
> If this is so then, the ALU becomes simpler when doing a FPGA core.

I'm not sure if I understand your question, but 6809 assemblers do not
convert SUB instructions to an ADDs using the two's complement of the
operand. That may be what happens inside the CPU when it sees a SUB


More information about the Coco mailing list