264 series questions

From: Nicolas Welte (welte_at_chemie.uni-konstanz.de)
Date: 1999-10-01 13:34:41

Maybe I will get more responses here. A while ago I asked on c.s.c about
the strange GATE IN signal input on the 264 series CPU, the 7501/8501.
Because I want to make a discrete replacement from a 6502, some '245
drivers and a port chip, maybe a 6522 for the first experiments. But
what does GATE IN do? One of the few Plus/4 resources mentions it as R/W
GATE input, so I assume it has influence on the R/W output of the CPU.
But why is it needed? Maybe because of the weird clock signals the TED
feeds into the CPU? If that is all, a simple AND gate should be enough
to do the same job. I really should have a look with an oscilloscope.

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