A communications interface on a data path between a plurality of data channels and a single communications port on a processor. The communications interface controls data as it passes on a receive path from the plurality of data channels to the single communications port and on a transmit path from the single communications port to the plurality of data channels and is adapted to use a memory to buffer the data when necessary. The communications interface (i) adds a channel identifier, which identifies to which data channel the data relates, to the data on the receive path so that the processor will be able to determine to which data channel the data relates and (ii) removes a channel identifier from the data on the transmit path so that the data will leave the communications interface in the same format in which it was received.