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

[Harry Hurst]

> Not sure if you have the undocumented opcode in on the 6809, opcode $3E.
>
> On all the official opcode maps it does not appear. If I remember
> correctly it will do a
> RESTART ( ie reset). The term RESTART appears in the programming manual
> from 1983
> as a hardware interrupt, (ie RESET). For some reason they added a software
> reset or
> RESTART that never made it to the official documentation.
>
> You can check it out by inserting into any code
>
> FCB $3E
>
> and see what it does.
>
>
>>From the old 6800 days there was HCF opcode that I am not sure translated
>> into the 6809 or
> not. Rumors has that it did. In the 6800 it was $DD. Not sure what it was
> in the the 6809 or
> even if it ws still there. $DD is STD in direct mode in the 6809. HCF or
> more commonly know
> as Halt and Catch Fire. It actually did not catch fire but the processor
> went into an address
> self test mode that had to be hard resetted to continue. There maybe other
> test mode
> opcodes that may or may not be there. Some may appear to do nothing but
> actually do
> something. The HCF opcode turns the address bus into a 16 bit counter.
> There maybe even
> one for the data bus. I know that 6811, 6805 and others based on those two
> have built in self
> test modes that are used in the testing of the die before and after
> packaging.
>

I've heard about the RESET. I've never tried it. There appear to be 3
HCF's on the 6809, opcodes $14, $15, and $CD. I've tried all of those and
their page $10 and $11 counterparts. They all work.

Go to this page:
https://sites.google.com/a/aaronwolfe.com/cococoding/home/docs

Download the "6x09_Instruction_Sets.pdf" there. It has all of this and
more, and it's laid very neatly.

Thanks,
HH