The DRV11-B Direct Memory Access Interface is a parallel port device controller for the QBUS which provided a pair of 16-bit parallel ports, one input, and one output; it uses DMA to transfer data.
It is effectively a half-duplex device; it has only a single pair of bus address and word count registers. Directional control is by the user's device specifying whether each cycle is a DATI, DATO, or DATIO.
It was a quad format card (M7950); connection to the user's device is via a pair of 40-pin Berg connectors.
Registers
The device has five control and buffer registers, which can be configured to any group of four sequential word locations in the I/O page; the first DRV11-B is normally configured to addresses 772410-72416. The two buffer registers share an address, responding to read or write cycles as the case might be.
| Register |
Abbreviation |
Address
|
| Word Count Register |
DRWCR |
767770
|
| Bus Address Register |
DRBAR |
767772
|
| Control and Status Register |
DRCSR |
767774
|
| Input Data Buffer Register |
DRINBUF |
767776 (read)
|
| Output Data Buffer Register |
DROUTBUF |
767776 (write)
|
In the register contents (below), bits which are read/write are shown in normal font, those which are read-only are in italics, and write-only in bold.
Word Count Register (DRWCR)
| WC15 <-> WC0
|
| 15
|
14
|
13
|
12
|
11
|
10
|
09
|
08
|
07
|
06
|
05
|
04
|
03
|
02
|
01
|
00
|
Bus Address Register (DRBAR)
| BA15 <-> BA1 |
0
|
| 15
|
14
|
13
|
12
|
11
|
10
|
09
|
08
|
07
|
06
|
05
|
04
|
03
|
02
|
01
|
00
|
Status Register (DRCSR)
| ERR |
NEX |
ATTN |
MAINT |
STATUS |
CYCLE |
RDY |
IE |
XAD |
FNCT |
GO
|
| 15
|
14
|
13
|
12
|
11
|
10
|
09
|
08
|
07
|
06
|
05
|
04
|
03
|
02
|
01
|
00
|
- ERR - Error; set by NEX or ATTN
- NEX - Nonexistent Memory; also write-to-zero
- ATTN - Attention; signal from user's hardware which can be tested, or cause an interrupt (below)
- MAINT - Maintenance
- STATUS - Signals from user hardware
- CYCLE - DMA cycle requested
- RDY - DRV11-B is able to accept a new command; set by ERR or WCR overflow, cleared by GO
- IE - Interrupt Enable - When set, allows setting RDY to cause an interrupt
- XAD - Extended Address; extension of BAR
- FNCT - Signals to user's hardware
- GO - Enables DMA, sent to user's hardware
Output Buffer Register (DROUTBUF)
| OUT15 <-> OUT0
|
| 15
|
14
|
13
|
12
|
11
|
10
|
09
|
08
|
07
|
06
|
05
|
04
|
03
|
02
|
01
|
00
|
Input Buffer Register (INBUF)
| IN15 <-> IN0
|
| 15
|
14
|
13
|
12
|
11
|
10
|
09
|
08
|
07
|
06
|
05
|
04
|
03
|
02
|
01
|
00
|
