DHV11 asynchronous serial line interface

DHV11 M3104 board

The DHV11 asynchronous serial line interface is the first QBUS equivalent to the UNIBUS DH11 (it was later replaced by the DHQ11). It provided 8 RS-232 asynchronous serial lines. Output used DMA (with each line having its own buffer pointer and count); input used a 256-character FIFO buffer.

Implementation

Physically, the DHV11 consisted of a single quad card, the M3104, connected to a pair of H3173-A distribution panels (4 lines each) via a BC05L flat cable, one per distribution panel; the BC05L connects to a 40-pin Berg header on each end. The H3173-A can be recognized by the DEC part number 50-15588-01 or -02 on its PCB; each contains four male DB-25 connectors (DB-25P). In addition to the usual '-xx' length indicators on the BC05L cable, it was also available in BC05L-1K (21 inch) and BC05L-2F (30 inch) lengths.

Device registers

The registers in the DHQ11 are somewhat different from those in the DH11:

• the QBUS has a larger address space than the UNIBUS, so it needs two word-sized registers to hold the output buffer address;
• the DHQ11 includes several microprocessors, and has extended capabilities, including a diagnostic sealf-test, and flow control support;
• the DHQ11 has the ability to transmit under program control.

Register	Abbreviation	Address
Control and Status Register	CSR	17760440
Receive Buffer Register	RBUF	17760442
Transmit Character Register	TXC	17760442
Line Parameter Register	LPR	17760444
Line Status Register	STAT	17760446
Line Control Register	CTRL	17760450
Transmit Buffer Address Register Low	TBADL	17760452
Transmit Buffer Address Register Hi	TBADH	17760454
Transmit Buffer Count Register	TBCT	17760456

The RBUF and TXC share an address; the RBUF is read only, and the TXC is write only. The TXC through TBCT are replicated, with one for each line in the device; the 'Line' field in the CSR indicates which one is currently available.

The addresses shown are for the first DHV11 in a system; additional ones are normally set to be at 17760460, 17760500.

Control and Status Register (CSR)

TXA	TXIE	DF	TDE	Unused	Tx Line			RDA	RXIE	MR	Unused		Line
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

• TXA - Transmitter Action
• TXIE - Transmit Interrupt Enable
• DF - Diagnostic Fail
• TDE - Transmit DMA Error
• Tx Line - Line which set TXA
• RDA - Received Data Available
• RXIE - Receive Interrupt Enable
• MR - Master Reset
• Line - Select TXC through TBCT

Line Parameter Register (LPR)

TSpeed				RSpeed				STOP	EVEN	PARE	CLEN		DICD		Unused
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

Line Status Register (STAT)

DSR	Unused	RI	DCD	CTS	Unused		DHU	Not Present
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

Line Control Register (CTRL)

Unused			RTS	Unused		DTR	LTYP	MAINT		FXOFF	OAUTO	BREAK	RXE	IAF	TXA
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

Further reading

• DHV11 Technical Manual, EK-DHV11-TM-001