Thanks for the input. I'll sign off and cogitate, but in the meantime,
here's a bit (heh) more:
I think the BCR connector could be used to monitor the status of all the
relays. A resistor (I used 33k) across the BCR (2-5 or 2-7) pins appears to
INP(187) as an "open" switch (a direct short appears as "closed"). The eight
status bits could be produced at the black box by just ( electronically)
throwing a resistor into the BCR sensing line for each "0" ( open) bit. Can
produce a timed 8-bit sequence. Timing would be handled at the box with a 555
timer, and by timing loops at the 100 end. Just one wire, because I think we
can use the RS232 ground.
But I haven't looked at the cassette interface diagrams yet. Could be all
sorts of goodies there too, huh?
I'm trying to keep this simple due to my own limitations. If any good
engineers wanted to colaborate, we could make the sucker sing!!!
Sounds gooder and gooder…
Do you have a copy of the Radio Shack Technical Manual for the M100? Catalog #
26-3810, $9.95. Has all the schematics, timing diagrams, etc that might be
useful to you.