Hi there people,

I seem to be the only person in the known universe that has one of these,
so I have managed to tap out the circuit to it, and am trying to understand
how everything works, however in typical 80's style, the designers seem to
have taken several shortcuts, such as incomplete address decoding, and
diode logic.

Anyway I'm currently trying to work out how the onboard rom is enabled, as
I would guess it also sits in the 0-16K reigon, as does the internal ROM.
However I am unclear as to the function of the /ROMCS line on the spectrum
expansion connector, looking at the spectrum schematic, it seems to be
generated by the ULA, but the disk interface also seems to maybe force it
high also (presumably to disable the internal ROM). Does this make sense ?

Is there a description somewhere of the meanings of the spectrum bus
signals, from what I remeber the manuals just list them, obviously the
majority are just Z80 signals that can be looked up on the Z80 data sheet.

Having now worked out the circuit for this interface, and entered it into
Eagle (PCB making program), is there anywhere that I can upload it, so that
others may have access to it if they ever need it (this asumes that I don't
have the only one in the known universe....).

Cheers.

Phill.