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

[jdaggett at gate.net]

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.  


james

On 21 Nov 2012 at 6:54, Harry Hurst wrote:

> I see what you mean, Luis. Chris got everything right, as far as I can
> see, up until page 7. That table on page 8 is a bit of a mess, though. I
> understand how he could easily have made that particular mistake, that
> opcode looks out of place in its proper position.
> 
> I have been looking at 6809 undocumented addressing modes, and have made
> up a table in a spreadsheet file. I am attaching it to this post.
> Hopefully, I will not have made any similar mistakes. There are two sheets
> in the file. The first is basically a duplicate of Darren Atkinson's
> opcode table. The second is the addressing modes table. Please let me know
> if I have made any errors.
> 
> HH
> 
> 
> 
> > LDQ = CD , not exits, instead there  STD, wrong
> > And other more errors
> > So in other documents.
> >
>