Memory !WR needs pull-up and anti-contention resistor

[jmacarthur]

!WR floats if BUSREQ is active and not pulled down by the front panel switch, so a 100k pull-up to 3.3V should be added. Because the Write button can be pressed while BUSREQ is inactive and the processor is in control of !WR, a resistor should be added between the button and the bus (1 kilohm?)

These are both present on the prototype but have not been added to the diagram.