COMMUNICATION MULTIPLEXER VARIABLE PRIORITY SCHEME

A communication multiplexer stores the receive and transmit channel numbers of input/output devices coupled to the multiplexer by communication lines in a first in-first out (FIFO) memory. The input/output devices are polled by sending the channel numbers from the FIFO to the input/output devices. An input/output device requesting service responds to its channel number. The remaining channel numbers in the FIFO are recirculated to give the receive channel numbers priority over the transmit channel numbers. This gives high priority to a most recently used receive channel operative in a burst mode and equal priority to all transmit channels.