DR11-A General Device Interface

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The DR11-A General Device Interface was a UNIBUS device controller which provided a pair of 16-bit parallel ports, one input, and one output.

It was a dual format card (M786), along with two standard single-width card FLIP CHIPs, the M105 Address Selector and the M782 Interrupt Control; they used an SPC slot.

Connection to the user's device is via a DEC backplane slot connector on one side of the card, into which two single-width paddle cards plugged.

The DR11-A was replaced by the single-board DR11-C general device interface. The DR11-C is upwardly compatible with the DR11-A for programming, but uses the cheaper and easier to work with Berg connectors.


The device has three control and buffer registers, which can be configured to any three sequential word locations in the I/O page; the first DR11-A is normally configured to addresses 777520-777524:

Register Abbreviation Address
Control and Status Register DRCSR 777520
Output Buffer Register DROUTBUF 777522
Input Buffer Register DRINBUF 777524

In the register contents (below), bits which are read/write or unused are shown in normal font, those which are read-only are in italics.

Status Register (DRCSR)

15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00

Output Buffer Register (DROUTBUF)

OUT15 <-> OUT0
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00

Input Buffer Register (INBUF)

IN15 <-> IN0
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00