The DRQ3B Replacement Module – M7658 (DCQ-1500) is a plug and play replacement for Digital’s DRQ3B Q-bus I/O controller. Like the DRQ3B, the DCQ-1500 is a high performance 16-bit parallel interface designed for realtime data collection or for high-speed interprocessor communications. It provides PIO and DMA transfers between a Q-bus system and external equipment at transfer rates of up to 1.3 mHz of 16-bit words.

The DCQ-1500 is hardware and software compatible with Digital’s DRQ3B. The module has two independent 16-bit channels for connection to external devices, allowing it to receive or send data or do both concurrently. Additionally, it can transfer data between two memory or I/O page locations.

The DCQ-1500 is a quad-width controller that can be installed in a variety of Digital’s PDP-11 and MicroVAX systems.

Data transfers are selectable as burst, block or extended block mode DMA. Interrupt priority levels are switch selectable and interrupt conditions are program selectable.