On Tue, Jan 30, 2018 at 11:18 PM, Mia Magnusson <mia@plea.se> wrote: > Addition: > > Also as 6502 afaik always drive the adress bus, you anyway need bus > separation between the 6502 and the video circuit, so the video ram > is anyway separate from the main ram. (The same is true for VIC-20, it > has buffers for both the adress and the data bus which is disabled > during the video halv of each cycle). sure, but I was talking about the few 2001 boards that use 2114 as main RAM too, so there's no address conflict in this case. Making sure the /WR signal to the RAM happens only when it's supposed to happen was too obvious, but I was rather asking why the selects wheren't qualified with PHI2, and the answer is that 6502 knows when to read the data bus anyway. I'm repairing a few 2001s lately. By the way, I can now read 6550s and 6540s in a custom microcontroller unit, so I can dump/test all the 6540s easily out of a PET board. I've discovered that my own two 6540 spares are actually only one spare by now :/ Frank Message was sent through the cbm-hackers mailing listReceived on 2018-01-31 00:00:03
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