DZV11 asynchronous serial line interface

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), holding DB25 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.)

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

Further reading

• DZV11 User Guide, EK-DZV11-UG-002
• DZV11 Technical Manual, EK-DZV11-TM-001