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3108 PIOC/256 (Programmable Input Output Controller) is an ND-100 I/O card with four full duplex serial lines. The hardware is based on an MC 68000 CPU, four Z80 SIO and 256 kbyte ram. There is also a smaller version with only 128 kbyte ram.


The new PIOC print, number 3108, is called PIOC-EXPANDED. The added function is X21 Clear Detection in hardware for lines 0 and 1. The print is produced in two versions:

  • PIOC/64 (64 Kbit memory chips)
  • PIOC/256 (256 Kbit memory chips)

Switches and indicators

The card has three thumb wheel switches numbered 3,2,1 from the top of the card. It has also three LED indicators, LD1 and LD2 red and LD3 yellow.

  • thumbwheel (position 12J) - PIOC number switch
  • thumbwheel (position 9J) - bank number (least significant)
  • thumbwheel (position 7J) - bank number (most significant)
  • LED 3 (yellow) - active memory cycle
  • LED 1 (red) - MC 68000 reset
  • LED 2 (red) - MC 68000 halt


The A and B connectors are used for I/O, the C connector is used for the ND-100 Bus.

I/O Devices on the card