Communication system message acknowledgement

摘要

A local communication system comprises a number of stations interconnected for the communication of messages via a serial data channel. A first station transmits a directed type of message to individual ones of the other stations, or transmits a broadcast type of message to all or a subset of the other stations. For a broadcast message, any receiving station unable to accept the message transmits (913) a common negative acknowledgement signal (NAK=1) and the first station re-transmits the message up to five times. Each receiving station may be unable to accept a message because its receive buffer is still occupied by a previous message. In such a case generation of the negative acknowledgement signal is suppressed if the message which cannot be accepted is judged identical to the message occupying the receive buffer of the receiving station. In this way, unnecessary communication is avoided, and certainty of communication is increased. <IMAGE>