DHV11 asynchronous serial line interface
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.
Contents
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
