DP11-A Synchronous Line Interface

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.

The modules are:

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:

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).