Redesign

I was not very happy with the last design as it was a bit of a "patch", so I redesigned from scratch. Here is the signals schematic:

As you can see, a write or mark signal is now automatic (no need to be programmed). The following move commands (S0 and S1) are no move, left, right or no move with write.

Here is the new full schematic:

It still needs to be checked and I have run out of 74HC194 chips so I will have to order some more (while the PCB is being made).

AlanX