U17 - 74LS138
  PKIB status out     10h (bit 0 and 2)
  PKIB data out       11h (8 bits)
  PKIB data in        12h (8 bits)


PKIP I/O map

U25 - 74LS138
out 0 - clear U35 FF (stop interrupt timer)
out 1 - set U35 FF (start interrupt timer)
out 2 - printer control (7 bits)
out 3 - printer control (7 bits)
out 4 - printer control (8 bits)
out 5 - keyboard control (8 bits)
out 6 - keyboard output latch (8 bits)
out 7 - keyboard output enable & set U12 FF2


U24 - 74LS138
in 0 - 
in 1 - 
in 2 - printer status (5/6 bits)
in 3 - 
in 4 - clear U30 FF2
in 5 - keyboard data (8 bits)
in 6 - printer input (8 bits from CPU board)
in 7 - clear main CPU interrupt (U30 FF1)

The ROM code only addresses port 6 (in & out) and port 7 (output) The code
to control the other ports must somehow come from the main CPU board.

/NMI - U36 LM555 interrupt timer