Multiple port communications adapter apparatus

A multi-port communications controller and variable protocol adapter is described. The adapter utilizes a user programmable pluggable programming cartridge for defining individual communications port data service characteristics. The port data service characteristics are interpreted by a microprocessor which manages the interchange from port to port and to or from memory or a host system. Direct memory access or interrupt driven memory access modes of operation are individually selectable for each individual in bound and out bound communications channel. The communications protocols employed at each port may be of any standard type with the microprocessor in the adapter making the appropriate conversion. Communication speeds can be automatically recognized and matched for each port also. An arbitration processor for both DMA and interrupt driven data transfer services is included as the heart of the communications adapter design to provide the capability of individualized control over each in bound and out bound channel's mode of data transfer service for the optimum mode of operation for each port and type of data service required.