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Re: RGB card
mojoehand wrote:
So far, I have verified that the 16-pin header is indeed for
connecting to an AppleColor 100 (or similar) TTL RGB monitor. The
corresponding signals match those on the 10-pin header with the DB9
connector. This means that the 10-pin header is not for connecting to
something on the Apple motherboard. That leaves the 2-pin J1 as the
only connector that might attach to something on the motherboard. I
still don't know what that might be, however.
I'm just starting to trace things out, but this is what I have so far.
Pin 1 of J1 goes to pin 9 of the 74LS175 (quad D flip-flop), which is
just below J1. Pin 9 on the LS175 is CP (clock). pin 2 of J1 goes to
pin 3 of the 74LS174 (hex D flip-flop), which is the middle chip
beneath the 10-pin header. Pin 3 on the LS174 is D0 (data). I know
this isn't much, and as I said, I'm just starting to trace this out.
Does this give a clue yet as to what J1 might connect to?
Hmmm--how about a clock (like 14MHz) and video...? It's strange,
though, that there is no ground on the connector--especially for
high-bandwidth signals.
A related question -- I know that slot 3 is different than the other
slots and is tied in with the Aux slot. I thought I read that slot 7
was also different and had something to do with video. Is this correct
(on a IIe) or did I misread something? I really need to find a
readable IIe schematic.
An RGB card for a //e would plug into the AUX slot. This card sounds
like it's intended for a ][ or ][+. (And, yes, it does have composite
sync and the color reference on slot 7 only.)
-michael
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