DZV11 asynchronous serial line interface

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DZV11 M7957 board

The DZV11 was a QBUS four port asynchronous serial line mux card for DEC computers; the QBUS equivalent of the UNIBUS DZ11 (with which it is program compatible). Like the original, it used used programmed I/O, and thus could present a considerable load on the CPU when running a high speed line.

A 64-entry FIFO buffer silo was provided on the input side. The DZV11 could operate with full-duplex modems. It provided program-set baud rates (up to 9600 baud), but not split speed. Break could be detected or generated on each line.

Implementation

Physically, it was a quad card, the M7957; a cable plugged into a 40-pin Berg connector header on the card led the lines out of the computer. The pin assignments in the Berg header are mirrored, so that if the mating Berg connector is plugged in backwards, the only result is to invert the line numbering.

Cabling

Initially, a special BC11U-25 cable was used; it consisted of 4 separate round cables, from a Berg connector, to individual DB25 male connectors (DB-25P) wired as DTEs.

A later alternative to the BC11U consisted of a flat cable from the Berg connector on the card to another on a 4-port distribution panel (DEC part number 70-19964) which held DB-25P male connectors. (The distribution panel may be recognized by the part number on its PCB, 50-15419; the part number for the complete assembly is 54-15420. An earlier version has PCB part number 50-14824, and assembly 54-14825.)

Device registers

Register Abbreviation Address
Control and Status Register CSR 760100
Receiver Buffer Register* RBUF 760102
Line Parameter Register* LPR 760102
Transmit Control Register TCR 760104
Modem Status Register MSR 760106
Transmit Data Register TDR 760106

The RBUF and LPR share an address, as do the MSR and TDR: the RBUF is read only, and the LPR is write only; the MSR is read only, and the TDR is write only. Registers marked with a '*' are word-width only, no byte operations.

The addresses shown are for the first DZ11 in a system (provided that there are no other devices in the floating device address space); additional ones are normally set to be at 760110, 760120, etc.

Control and Status Register (CSR)

TRDY TIE SA SAE Unused Tx Line RDONE RIE MSE CLR MAINT Unused
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
  • TRDY - Transmitter Ready
  • TIE - Transmitter Interrupt Enable
  • SA - Silo Alarm
  • SAE - Silo Alarm Enable
  • Tx Line - Line ready to transmit
  • RDONE - Received Done
  • RIE - Receiver Interrupt Enable
  • MSE - Master Scan Enable
  • CLR - Clear input FIFO, CSR and UARTs
  • MAINT - Maintenance loopback enabled

Receiver Buffer Register (RBUF)

DV OVR FRERR PERR Unused Rx Line RBUF
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00

Line Parameter Register (LPR)

Unused RXON Speed ODDP PAREN STOP CLEN Unused Line
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00

Transmit Control Register (TCR)

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

Modem Status Register (MSR)

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

Transmit Data Register (TDR)

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

Details information

The DZV11 uses the DEC LSI-11 Bus interface chips; the DZV11 technical manual (below) includes detailed descriptions of all of them in Appendix A, 'IC Descriptions' - along with a detailed description of the UART chip, used across essentially all DEC asynchronous serial line cards of this generation.

External links

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