[Coco] 6309 instruction timing question

William Astle lost at l-w.ca
Wed Aug 27 17:46:56 EDT 2008


Darren A wrote:
> Good point.  It's interesting that the BRA instruction always uses the
> same number of cycles, but LBRA uses one fewer in native mode.

Probably because the 6309 can do 16 bit additions in 1 cycle while the
6809 required 2 cycles. That seems to me to be the reason why long
branches take 1 more cycle to execute when the branch is taken on the 6809.

> By the way, if you are relying on the Chet Simpson document for your
> timing reference, you should know that some of the information is
> incorrect (mainly the indexing modes involving W).

I don't have anything that I can make heads or tails of other than one
or more versions of that document. No amount of Google-Fu has revealed
anything else to me. If you can point me to something accurate, I would
be grateful.

> 
> Darren
> 
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