With all three parallel ports in use, we have to add another 12 bits of output. Using an external dual 8-bit latch, and the data and command control lines, can we output our 12 bits to that latch? How?
I think you’ll have to create yourself a “local” data bus and directly manipulate port signals to write data to the outputs. Might be simpler to just create an output port off the main data bus - especially if you’ve got a spare chip select. Steve