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.
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.
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.
|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 - 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
- DHV11 Technical Manual, EK-DHV11-TM-001