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3039 is the ND-100 bus controller.


What does it do?

Switches and indicators

  • short timeout indicator (lit if short timeout is selected)
  • timeout selector
    • short timeout (2 mS)
    • long timeout (8 mS)

A BUSC controlling a memory bank should have a short timeout. A BUSC controlling an I/O bus should have a long timeout.

  • ADOK - Address OK indicates which bank the last master-bus cycle was accessing. It is reset by start of next master-bus memory cycle.
  • extended device-number switch
  • interleave selector
  • device number
  • Base-setting display
  • Upper-limit display
  • Lower-limit display
  • Base address switches
  • Upper limit switches
  • Lower limit switches

For Base, Upper and Lower limit switches: the most-significant switch is topmost, and the least-significant switch is closest to the bottom of the card. The address area for a bus controller is decided by the setting of lower and upper address limit. The limit-address increments are 64K units.


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