On Mar 4, 2010, at 9:40 AM, Jeff Walther wrote:
Well, carp. All of the above was wrong. I looked at a memory
datasheet. RAS stays low during the whole operation. So one needs a
state machine which only let's WE go low if RAS went low first. If
CAS went low first then WE must be kept high. I'm not quite sure
how the state machine would reset, though. Maybe whenever RAS goes
high again.
IIRC, a PAL16R4 could do the job.
These were eventually made fast enough to be employed in the way
described, intercepting *RAS, *CAS, *WE and whatever else was needed,
and to output *RAS', *CAS', *WE' .
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