DP11-A Synchronous Line Interface

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The DP11-A is the earliest synchronous serial line interface for the UNIBUS; it uses programmed I/O to transfer data.

It was intended to interface to Bell 201, 301 and 303 series modems.

It was constructed from a number of smaller FLIP CHIPs, along with a larger board, which were installed in custom 4-slot backplane system unit.

Registers

Register Abbreviation Address
Receiver Control and Status Register DPRCSR 774770
Receiver Buffer Register DPRBUF 774772
Sync Register DPSYNC 774773
Additional Sync Register DPASYNC 774777
Transmitter Control and Status Register DPRCSR 774774
Transmitter Buffer Register DPRBUF 774776

The two SYNC registers seem to overlay the buffer registers; this is not yet sorted out.

The addresses shown are for the first DP11-A in a system; additional ones are normally set to be at 774760, 774750, etc to 774400.

Implementation

The modules are:

  • M105 - UNIBUS Address Selector Module
  • M239 - Divide by 16 Module (optional)
  • M405 - Clock Module (optional)
  • M594 - Level Converter Module
  • M7820 - Interrupt Control
  • M7065 - Receiver Module (two)
  • M7075 - Transmitter Module (two)
  • M7223 - Control Module

The M7223 is a quad card; the others are all single. (Of those, the M796 and M7820 are extended length; the M239 and M405 are standard length.)

The M594 can be substituted with other adapter cards from the DF11 series; in particular, the M595 is used with the Bell 303 series modem.

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

Connector
Slot A B C D E F
1 UNIBUS In M7223
2 G8000 Filter   M105 M7820 M405 M239
3 Power   M7075 M7065 M7075 M7065
4 UNIBUS Out Modem connector Level Converter

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