DR11-B parallel interface
The DR11-B was a parallel interface for the UNIBUS, one which used DMA to transfer data to a user device.
The interface between the DR11-B and the user device uses a number of unidirectional control lines (below), which control data transfer; and sets of three 'status' and 'control' lines, which appear in the Status and Command Register. By appropriate manipulation of the control lines, the user device can do byte or word cycles on the bus, perform read-modify-write bus cycles, or do block 'burst' bus transfers.
Data going to the user device is buffered in a set of latches; data coming from the user device is not buffered, and must be held valid for the duration of the resultant bus cycle.
Registers
| Register | Abbreviation | Address |
|---|---|---|
| Word Count Register | DRWC | 772410 |
| Bus Address Register | DRBA | 772412 |
| Status and Command Register | DRST | 772414 |
| Data Buffer Register | DRDB | 772416 |
The addresses shown are for the first DR11-B in a system; additional ones are normally set to be at 772430, 772450, 772470, etc.
772410: Word Count Register (DRWC)
| WC15 <---> WC00 | |||||||||||||||
| 15 | 14 | 13 | 12 | 11 | 10 | 09 | 08 | 07 | 06 | 05 | 04 | 03 | 02 | 01 | 00 |
772412: Bus Address Register (DRBA)
| BA15 <---> BA00 | |||||||||||||||
| 15 | 14 | 13 | 12 | 11 | 10 | 09 | 08 | 07 | 06 | 05 | 04 | 03 | 02 | 01 | 00 |
772414: Status and Command Register (DRST)
| ERROR | NEX | ATTN | MAINT | DSTAT A-C | CYCLE | READY | IE | XBA16-17 | FNCT1-3 | GO | |||||
| 15 | 14 | 13 | 12 | 11 | 10 | 09 | 08 | 07 | 06 | 05 | 04 | 03 | 02 | 01 | 00 |
772416: Data Buffer Register (DRDB)
| Data15 <---> Data00 | |||||||||||||||
| 15 | 14 | 13 | 12 | 11 | 10 | 09 | 08 | 07 | 06 | 05 | 04 | 03 | 02 | 01 | 00 |
Note: Unlike most DEC DMA devices, an overflow in the Bus Address Register does not carry into the Extended Memory bits in the CSR.
User Device Interface
User Input Signals
| Signal Name | Count | Function |
|---|---|---|
| DAT IN | 16 | Data from user device |
| CONTROL | 2 | Specify type of UNIBUS cycle (DATI, etc) |
| CYCLE REQ | 2 | Either one can set the CYCLE bit, which causes a bus cycle |
| WC INC ENB | 1 | Word Count Increment Enable |
| BA INC ENB | 1 | Bus Address Increment Enable |
| A00 | 1 | Bus Address Bit 0 |
| DSTAT | 3 | Device Status Bits |
| ATTN | 1 | Attention bit in the DRST |
| SINGLE CYCLE | 1 | Controls use of burst mode for bus cycles |
User Output Signals
| Signal Name | Count | Function |
|---|---|---|
| DAT OUT | 16 | Data to user device |
| INITIALIZE | 1 | UNIBUS INIT or interlock error |
| FNCT | 3 | Function bits in the DRST |
| READY | 1 | READY bit from the DRST |
| BUSY | 1 | Bus cycle in progress |
| END CYCLE | 1 | Bus cycle is complete |
| GO | 1 | GO bit from the DRST |
Implementation
It was constructed from a number of smaller FLIP CHIPs which were installed in custom 4-slot system unit backplane.
The extant DR11-B documentation does not show either the modules used in the DR11-B, or their locations in the backplane, so that information is given here.
The modules are:
- M112 - 10 x 2-input NOR gates
- M113 - 10 x 2-input NAND gates
- M116 - 6 x 4-input NOR gates
- M205 - 5 x 'D' flip-flops
- 2 x M208 - 8-bit buffer / shift-register
- M239 - 3 x 4-bit counter/register
- 2 x M611 - High speed power inverters
- M796 - UNIBUS Master Control
- M7821 - Interrupt Control
- M7219 - Bus Interface
The M7219 is a quad card; the others are all single. (Of those, the M796 and M7821 are extended length; the others are all standard length.) The M239 is used to hold the Command and Status Register.
Board locations (as seen from the board insertion side of the backplane, not the wire-wrap pin side, as is common in DEC documentation) are:
| Connector | ||||||
|---|---|---|---|---|---|---|
| Slot | A | B | C | D | E | F |
| 1 | UNIBUS In | M7219 | ||||
| 2 | Test board | M208 | M208 | M7821 | M796 | |
| 3 | Power | M205 | M611 | M611 | M112 | M113 |
| 4 | UNIBUS Out | User connector | M116 | M239 | ||
Connection to the user device is via either a pair of M957 Split-Lug Cable boards, or via an M9760 (dual) Twisted Pair Cable Connector board. The M9680 (dual) board is a loopback test board, which can be inserted in place of the user connection board(s).
Power comes in on a single-width stub card in the A3 slot (as is canonical in the PDP-11/20 generation of PDP-11s).
Further reading
- DRll-B Engineering Drawings - not online at this time
External links
- DR11-B/DA11-B manual (DEC-11-HDRBA-D-D)
- DR11-B/DA11-B manual (EK-DR11B-TM-004)
