DS11 Multiple Line Synchronous Interface

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The DS11 Multiple Line Synchronous Interface was an early synchronous serial line interface for the UNIBUS; it could handle up to 16 lines. It used programmed I/O (with separate receive and transmit interrupts) to transfer data; it could operate in either half-duplex or full-duplex mode.

Character lengths of 6, 8 and 12 bits were supported, and could be configured by software. It provided an EIA RS-232 interface to Bell 200 series modems (such as the model 201, and equivalents), and also connect to Bell 300 series modems, such as the model 303.


Register Abbreviation Address
Receiver Status Register RxCSR 775xx0
Receiver Data Buffer Register RxDBUF 775xx2
Transmitter Status Register TxCSR 775xx4
Transmitter Data Buffer Register TxDBUF 775xx6

Line addresses:

  • Line 0: 775400-775406
  • Line 15: 775570-775576


The DS11 consisted of a master line scanner, and up to four adapters, each of which could handle up to four lines; each line had a separate quad M7110 Line Control Module. Physically, it is a large quad-height backplane, mounted in a 19" cabinet such as an H950, along with the DS11's DEC indicator panel.

The DS11, like some other early UNIBUS peripherals, was made of many small FLIP CHIPs. The inventory of the card types in the DS11 is:

  • G830 5V, 10A Regulator from 8V
  • M002 Resistor network
  • M126 6 x AND-NOR Gates
  • M128 4,4 AND-NOR Gates
  • M139 3 x 8-Input NAND Gates
  • M143 10 x 2-Input NAND Gates
  • M145 7 x 3-Input NAND Gates
  • M147 5 x 4-Input, 1 x 2-Input NAND Gates
  • M152 Dual Non-inverting Binary to Octal with Enable
  • M165 Memory buffer, Inverting and Non-inverting Output
  • M171 2-2-2-3 AND-NOR
  • M173 10 x 2-input AND gates
  • M174 4 En x 9 out mixer
  • M175 7 x 3-input AND gates
  • M177 5 x 4-Input AND Gates
  • M178 8 En x 6 out mixer
  • M181 Non-inverting 2-2-2-3 AND-NOR
  • M211 6-Bit Up/Down Counter
  • M241 6 x D Flip-flops with common clock
  • M243 8 x D Flip-flops with 2 common clocks
  • M246 5 x D Flip-Flops
  • M253 16 Word, 12-bit Memory
  • M307 Integrating One Shot
  • M321 Tapped Delay Line
  • M362 Delay, 25 to 50 ns
  • M401 Variable Clock
  • M603 Pulse Amplifiers
  • M612 6 Power Gates
  • M783 UNIBUS Drivers
  • M784 UNIBUS Receiver
  • M785 UNIBUS Transceiver
  • M931 15 Terminators
  • M969 24 Level Terminators
  • M511 UNIBUS Receivers - sources differ as to whether or not this is used
  • W990 Connectors
  • M105 Address Selector - used to set its bus address
  • M7820 Interrupt Control
  • M7110 Line Control Module - one per line

The number of each type used is currently unknown; likewise the locations in the backplane (except the M7110's)

See also

Further reading

  • DS11 Multiple Line Synchronous Interface Maintenance Manual (DEC-00-DS11-DB; not available online, but in fiche)

External links