DQ11 NPR Synchronous Line Interface

The DQ11 is the earliest DMA synchronous serial line interface for the UNIBUS. The base unit, the DQ11-DA/EA, was double-buffered, and used separate receive and transmit interrupts to signal completed transfers of data. One optional expansio, the DQ11-AB, provided CRC computation in hardware. (It supported byte-oriented protocols, e.g. BISYNC.) For error detection, a variety of CRC algorithms, depending on the protocol in use on the line, were supported. Another optional expansion, the DQ11-BB, provided programmable character detection in hardware, for functions such as DLE stuffing.

It provided an EIA RS-232 interface (to Bell 200 series modems, such as the model 201, and equivalents), and optionally a current loop interface (to Bell 300 series modems, such as the model 303, and equivalents). Baud rates of up to 10K bits/second were supported by the EIA interface, and up to 1M bits/second by the current loop interface.

The character length (up to 16 bits), and the sync character, were selectable. It could operate in either half-duplex or full-duplex mode. All configuration, as well as all the modem control leads, could be set under program control.

Optionally, the DQ11-KA allowed use of an internal clock (when two interfaces were connected directly, without modems).

Registers

Register	Abbreviation	Address
Receive Status Register	DQRxCSR	76xxx0
Transmit Status Register	DQTxCSR	76xxx2
Reg/Err Register	DQRER	76xxx4
Shadow Register(s)	DQSR	76xxx6

The addresses shown are for the first DQ11 in a system's floating device address space; additional ones are normally set to be immediately following.

The DQ11 has a set of 16 'shadow' registers, access to which is gained by placing the shadow register number in the appropriate bits in the DQRER, and then reading/writing the DQSR. (The DQ11 documentat8on refers to these as 'secondary' registers, but this is confusing, as the shadow register set contains "primary" and "secondary" registers; the term 'shadow' has therefore been adopted here.) The shadow registers are:

Register	Function
0	Receive Bus Address - RxBA (Primary)
1	Receive Character Count - RxCC (Primary)
2	Transmit Bus Address - TxBA (Primary)
3	Transmit Character Count - TxCC (Primary)
4	Receive Bus Address - RxBA (Secondary)
5	Receive Character Count - RxCC (Secondary)
6	Transmit Bus Address - TxBA (Secondary)
7	Transmit Character Count - TxCC (Secondary)
10	Character Detect - CHARDET
11	Sync Character - SYNC
12	Miscellaneous - MISC
13	Transmit Buffer - TxBUF
14	Sequence - SEQ
15	Receive Block Check Character - RxBCC
16	Transmit Block Check Character - TxBCC
17	Receive/Transmit Polynomial - RTP

Implementation

It was constructed from a number of smaller FLIP CHIPs, along with several larger boards, which were installed in a custom 4-slot backplane system unit (DEC part number 70-09467). Installation of the DQ11-AB or DQ11-BB required an additional 4-slot backplane (part number 70-09468), connected to the first one via 3 BC08S flat cables connected to M971 Cable Connector cards. It used one of the DF11 Communications Line Adapter‎s to interface to the modem.

The modules for the basic unit are:

• M105 - UNIBUS Address Selector Module
• M7821 - Interrupt Control
• M7812 - Bus selectors, CSRs, shift registers
• M7813 - Character count, bus address, shift control
• M7815 - Modem control
• M7818 - Hardwired character detection and NPR control

The EIA interface (DQ11/DA) includes:

• M594 - EIA Level Converter Module

The 20 mA interface (DQ11/EA) includes:

• M595 - 20mA Converter Module

The modules for the options are

• M7816 - Block check (DQ11-AB)
• M7817 - Programmable character detection and sequence control (DQ11-BB)
• M4050 - Crystal Clock Module (DQ11-KA)

The M7812, M7813, M7816 and M7817 are hex cards; the M7818 is dual, and the M7815, M105 and M7821 are single. (All are extended length.)

Board locations (as seen from the board insertion side of the backplanes, not the wire-wrap pin side, as is common in DEC documentation) are (main backplane):

	Connector
Slot	A	B	C	D	E	F
1	UNIBUS In		DF11 Cable	DF11 Converter	M7815	M105
2	M7812
3	M7813
4	UNIBUS Out		M7821	M4050@	M7818@

@ = M971/BC08S if DQ11-AB/DQ11-BB installed.

Board locations (DQ11-AB/DQ11-BB backplane):

	Connector
Slot	A	B	C	D	E	F
1	UNIBUS In		M4050	M971/BC08S	M971/BC08S	M971/BC08S
2	M7816
3	M7817
4	UNIBUS Out		Unused		M7818