[Coco] 6809 Push/Pull

[Arthur Flexser]

The bits in the postbyte just tell the 6809 WHICH registers are involved,
not the order of anything.  The order of pulling is the reverse of pushing,
so the registers get back to what they were originally when the same
registers are listed (regardless of order) in the push and pull
instructions.  The postbyte is identical for PSHS X,Y and PULS X,Y;  only
the opcode differs.

Art

On Fri, Jun 5, 2020 at 6:16 PM Lee <leep at tigerbase.com> wrote:

> Just out of curiosity (I could look it up), is the order of the registers
> in the bits reversed for pull compared to push?  If so, I wonder if that's
> an optimization so the processor can read the bits the same direction for
> each instruction?  Just guessing.
> -----
> Lee
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