DM11-BA Modem Control Multiplexor
The DM11-BA Modem Control Multiplexor allows synchronous and asynchronous serial lines connected to a UNIBUS device controller to be connected to modems. It could be set to interrupt the CPU when a modem control line (Ring, Carrier, etc) changed state.
It is a re-implementation of the DM11-BB Modem Control Option; however, instead of plugging into a controller backplane like the -BB, the -BA plugs into a standard UNIBUS MUD slot. It is program compatible with the DM11-BB (although a single DM11-BA only supports 8 lines, unlike the DM11-BB, which handled 16).
It is implemented as a single hex board, the M8640. Its interrupt vector and register addresses are set by a pair of DIP switches (and a jumper (W1) for one bit of the address, on etch revision B boards). A UNIBUS priority plug is also present.
It connects, using two flat cables plugged into Berg headers on the board, to a passive distribution panel; either the H317-M or the functionally identical H317-P (the latter has improved EMI shielding).
Further reading
- DM11-BA Modem Control Multiplexor (YM-C138C-00) - not online
External links
- KMS11-BD/BE Synchronous Communication Processor User Guide (EK-KMSBE-UG-001) - contains moderately detailed information on the DM11-BA in various places
