On 12/28/2016 10:06 AM, Gerrit Heitsch wrote: > > > You can do that, yes, since VIC will not access the KERNAL ROM. But > you still need to take the possibility of a badline in the middle of > the vector fetch into account. I don't think I do. access $fffd (jmp) <lots of time elapses for VIC badline> access $fffd (low byte of vector) ... From the logic's point of view, they are two consecutive reads from ROM, regardless of the time elapsing between them. So, as long as you're not depending on timing, but rather a state machine: if (!oe and state = 0 and $1ffd) state = 1 if (!oe and state = 1 and $1ffe) state = 2 else state = 0 if (!oe and state = 2 and $1fff) state = 3 else state = 0 Seems like it would work. Of course, you have to ensure that all reset vectors in the ROMs you are using are valid targets in the "boot rom", since the CPU could fetch any of the vectors, depending on which ROM is active, but that seems OK. Jim Message was sent through the cbm-hackers mailing listReceived on 2016-12-28 18:01:36
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