Re: Mk14 vdu
I had a thought last night about NRDS signal from the VDU - the pin which supplies this signal from the PIC-VDU will need to 'disconnect' from the bus when the VDU is inactive otherwise it will fight with the NRDS signal from the SC/MP.
On the real VDU this is handled by using a pullup resistor and reverse-biased diode on the output of the gate which supplies NRDS, to make it 'look' like an open-collector output.
You can do the same with your PIC output or you can leave the output latch for that port pin set to '0' and flip the pin mode between input and output to simulate the open-collector action.
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