[Coco] 6809 / General CPU question

Darren A mechacoco at gmail.com
Thu Feb 24 19:12:18 EST 2011

On 2/24/11, jdaggett at gate.net <jdaggett at gate.net> wrote:
> It was documented but in a odd way. If you look at the programming manual at
> the end of the instruction set description there is RESTART or hardware
> reset. Executing that opcode ($3E) will set the I and F bits in the CCR,
> clear the DPR and fetch the reset vector. This is essentially what happens
> when one pushes the reset button or issues a $3E opcode.
> james


The $3E opcode is never mentioned in Motrola documentation. The page
you cited in the programming manual is describing what happens when
the RESET pin is asserted (Hardware Interrupt), just as the preceding
pages describe the effects of asserting IRQ, FIRQ and NMI.


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