DHQ11 asynchronous serial line interface

The DHQ11 asynchronous serial line interface is the second QBUS equivalent to the UNIBUS DH11 (it a replacement for the DHV11). It provided 8 RS-232 asynchronous serial lines. Output used DMA (with each line having its own buffer pointer and count); input used a 64-character FIFO buffer.

It can be set (via a switch) to emulate either a DHV11 or DHU11.

Implementation

Physically, the DHQ11 consisted of a single dual card, the M3107, 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 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 will depend on whether it is emulating a DHV11 or DHU11.

Control and Status Register (CSR)

In DHU11 mode, the CSR is:

TXA	TXIE	DF	TDE	Unused	Tx Line			RDA	RXIE	MR	SKIP	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
• SKIP - Skip Self-Test
• Line - Select TXC through TBCT

Further reading

• DHQ11 User Guide, EK-DHQ11-UG-002