Abstract: A data communications subsystem operates with a main host computer having a central processor and main memory. The subsystem comprises: A data communications processor having its own internal memory for storing data transfer routines; and autonomous memory dedicated to storing data transfer instructions and control data; and a basic control module which includes a basic control interface unit connecting a plurality of front-end controllers. The basic control interface unit provides memory access paths for the front-end controllers to access data communications memory resources. The data communications processor provides address pointers to each of the front-end controllers whereby the selected front-end controller may access data transfer instructions from a data communications memory resource and then execute these instructions. The data transfer instructions are stored in "command blocks" in a memory resource and are made accessible to the front-end controllers for execution of data transfer operations.