DRV11-WA General Purpose DMA Interface

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DRV11-WA board

The DRV11-WA Direct Memory Access Interface is a parallel interface 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 a Q22 device.

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 dual format card (M7651); connection to the user's device is via a pair of 40-pin Berg connectors.


The device has six control and buffer registers, which can be configured to any group of four sequential word locations in the I/O page (two pairs of registers share an address); the first DRV11-WA is normally configured to addresses 772410-72416.

Register Abbreviation Address
Word Count Register DRWCR 767770
Bus Address Register DRBAR 767772
Bus Address Extension Register DRBAE 767772
Control and Status Register DRCSR 767774
Input Data Buffer Register DRINBUF 767776 (read)
Output Data Buffer Register DROUTBUF 767776 (write)

To gain access to the BAE, reference the BAR; this sets an internal flag which sends the next reference to the BAR's address to the BAE. Referring to any register (e.g. reading the WCR) clears the flag. The two buffer registers share an address, responding to read or write cycles as the case might be.