DR11-B parallel interface

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The DR11-B was a parallel interface for the UNIBUS which used DMA to transfer data.


It was constructed from a number of smaller Flip Chips which were installed in custom 4-slot backplane system unit. The extant DR11-B documentation does not show either the modules used in the DR11-B, or their locations in the backplane, so that information is given here.

The modules are:

  • M112 - 10 x 2-input NOR gates
  • M113 - 10 x 2-input NAND gates
  • M116 - 6 x 4-input NOR gates
  • M205 - 5 x 'D' flip flops
  • 2 x M208 - 8-bit buffer / shift-register
  • M239 - 3 x 4-bit counter/register
  • 2 x M611 - High speed power inverters
  • M796 - UNIBUS Master Control
  • M7821 - Interrupt Control
  • M7219 - Bus Interface

The M7219 is a quad card; the others are all single. (Of those, the M796 and M7821 are extended length; the others are all standard length.) The M239 is used to hold the Command and Status Register.

Board locations (as seen from the board insertion side of the backplane, not the wire-wrap pin side, as it common in DEC documentation) are:

Slot A B C D E F
1 UNIBUS In M7219
2 Test board M208 M208 M7821 M796
3 Power M205 M611 M611 M112 M113
4 UNIBUS Out User connector M116 M239

Connection to the user device is via either a pair of M957 Split-Lug Cable boards, or via an M9760 (dual) Twisted Pair Cable Connector board. The M9680 (dual) board is a loopback test board, which can be inserted in place of the user connection board(s).

Power comes in on a single-width card in the A3 slot (as is canonical in the PDP-11/20 generation of PDP-11).