For those with 6809 experience

Jim Brain brain at
Thu Mar 5 20:11:04 CST 2020

On 3/3/2020 8:39 AM, osi.superboard via cctalk wrote:
> My assumption is, that the LDA address access is too late at the end 
> of the instruction cycle, and the CPU already started the next 
> instruction cycle internally. HALT will be acknowledged only during 
> the instruction cycle following the LDA.
> It would be interesting to measure, when the LDA pulls down the HALT 
> compared to the last instruction cycle signal (LIC). Maybe using LDD 
> will work better, because the HALT signal will be asserted one clock 
> before the instruction cycle ends.

Which is exactly what I ended up doing:


More information about the cctech mailing list