[Coco] 6309/6809 opcodes with mixed 8/16 bit registers

[Harry Hurst]

>
> FWIW, I also have
>
> 1RRI1010 ($8A, etc.) -> ea = REG_PC | 0xff
>
> (ie, PC with the lower 8 bits set to 1).
>

Weird, but verified. The "I" bit does do indirection, at least in the case
of $9A and $BA.

> Strangely though, I have $87 etc. down as being zero-offset (ie a
> duplicate of $84, etc.), so it looks like I have to re-verify everything!

I pretty certain of the A,R duplication. Perhaps you had a 0 in the A
register when you were checking this?

>
> I don't have anything noted for 1RRI1110 ($8E, etc.).
>

Everything I've tried so far for 1RR01110 has returned an EA of $FFFF.
Indirection, 1RR11110, returned the contents of that same address and the
next byte, $0000. Might be useful for determining what CPU is running.
Otherwise, not so much.

1RRI1111 ($8F, etc.) returns the address in the immediate word after this
instruction. The indirect bit works in this case as well.

Thanks,
HH