Hallo Spiro, > There are two reasons why you can't use a simple latch: > > 1. You've got to emulate the behaviour of the DDR at $0000, too. > So I has got to be a more sophisticated latch. (I don't know > the 373, so I cannot say if it would handle this correctly). The circuit only uses P1 which is an output after the I/O initialisation. And I don't know of any program changing it for any reason. > 2. The 6510 handles $0000 and $0001 internally, so read and write > access cannot be seen from outside. That is what I think as well. But if there is nothing to be seen on the address- or databus, how does this external 6510 know what to do ?????? > That's the main reason why a 6510 is used: It always exe- > cutes the same opcode and data as the internal 6510, so any store > to $0000 or $0001 is the same as internally, so the on-chip port > provides the same information as the one of the internal 6510. What you're saying is that the external 6510 is executing the same program as the internal one? I never had thought about that. I thought that it was "sleeping" or whatever because its busses had been disabled. If the above is the case, then next question: are all produced 6510's the same and if not, does that matter in this case? Groetjes, Ruud - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail email@example.com.
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