On 7/18/2014 1:41 PM, Gerrit Heitsch wrote: > > > To remedy that you need a command sequence that makes sure a certain > Byte WILL be executed as a command, from then on you know the internal > state of the CPU and it becomes easy. That's what I supplied with the > BIT command. Since with a long enough sequence of NOPs, there are only > 2 alternatives, it will be either the first or the second: > > EA EA EA EA 24 EA EA A9 00 > > ex -- ex -- ex -- -- ex -- > > -- ex -- ex -- ex -- ex -- > > > Either way, A9 will be executed as command and the accu will be loaded > with #$00. Yes, I want to call this out. This was the other piece that made me more confident that success could be achieved. I think this, coupled with Greg's suggestion, made the solution clear to me. > > The other thing I remember was that the 6500/1 does divide the > externally supplied clock by two. But the longer I think about it, the > less I see that as a problem as long as you feed the bytes at the > right speed (meaning half the clockspeed), the clock phase is of no > consequence as long as the data read by the CPU is stable the moment > it's sampled. Yep, I agree. I saw your concern, but I figured just leaving the data there for both cycles would ensure success. Jim Message was sent through the cbm-hackers mailing listReceived on 2014-07-19 01:01:09
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