Posted By
TLC
on 2007-01-09
10:21:25
|  Re: Plus/4 Expansion port...
Solder: I don't actually know the MMU in the TED well... I just followed the line of the schematics (it might be slightly badly reverse engineered, still, it looks very likely that it's possible to fool the MMU logics with a simple trick like that assertion of A9... I haven't actually been aware of this phenomenon previously). Banking in the EPROM immediately looked still suspicious to me (for an EPROM to work, some time is needed for things to settle, at least if the CS' line is used for selecting the chip; but thinking it over again, it'd be enough if the CS' of the EPROM was controlled by something like the A15, continously (which doesn't harm anything as long as OE is not asserted), and "banking in" the thing went by asserting OE' (which is quick, and has no dependency on any other conditions).
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