[Coco] HD63x09 Question

[Roger Taylor]

At 10:03 AM 1/5/2005, you wrote:
>to the 6309 experts:
>
>I recently obtained 4 HD63C09EP chips and was looking at doing a
>project with them. I did a Google search and found the original post
>to comp.sys.m6809 group by Hirotsugu Kakugawa. Between that
>memo and Chet Simpson's technical manual I have some needs to
>confirm what I suspect:
>
>1) that the increased instruction set is available in either "emulated"
>or "native" modes and that

The 6809 mode is an emulation mode of the 6309.  For compatibility, it's 
the default state the CPU starts up in.  By switching to native mode, 
you're telling the 6309 to not try to act completely like a 6809, but to 
allow faster cycles and various other enhancements.



>2) the MULD and the DIVD and DIVQ instructions due signed math
>and not unsigned!
>
>This seems odd as the MUL instrtuction of the 6809 is unsigned. IF
>the new math opcodes are indeed signed math then I will  have to
>do some extra manipulation since  I am doing unsigned math.


The 32-bit signed DIVQ instruction is great for 16-bit unsigned math.  No 
extra manipulation is required except the MSBit of Q must be clear, ofcourse.


-- 
Roger Taylor