Hello! Jim Brain wrote: > My suspicions are the RDY > or AEC or some other signal forcing the bus to go tristate, but I am not > yet able to test that. But the 6502 does not have any signal for tri-stating the bus; also, if the data bus was tri-stated, the address bus would be too. This must be something else going on. My initial ideas: * Your CPLD is messing with the data bus somehow, and 6509 tolerates it but 6502 doesn't. You said that the CPLD is "doing nothing" - what dies it exactly mean? Is it not programmed at all, or programmed with some dummy code? * Something else is driving the data bus and 6509 has stronger drivers which can overcome it, but 6502 doesn't (OK, this doesn't seem likely to me, but it's a distant possibility). I would try placing a 74LS245 between the 6502 and the data bus. Regards, Michau. Message was sent through the cbm-hackers mailing listReceived on 2018-02-27 12:00:03
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