TRANSPARENT MULTIPLEXER COMMUNICATION TRANSMISSION SYSTEM

摘要

A communication multiplexing apparatus including scanning circuits and control circuits operatively couples an input/output data processing device to a plurality of input/output data units through a plurality of common interface lines for transmission and reception of data. The multiplexing apparatus is completely transparent to data processing device and input/output units as it recognizes no special characters within the data being transmitted. An input/output unit initiates a transmit operation by forcing a first control line to a predetermined state which causes scanning apparatus to stop when it encounters the line of the active unit. In accordance with the state of the scanning circuits, control circuits enable the control lines of the selected active input/output unit for a data transfer operation and disable the control lines of all remaining units. The multiplexing apparatus permits the data processing unit to initiate a transaction with an input/output unit by transferring all of the message signals transmitted by the data processing unit to each of the input/output units simultaneously. When the input/output recognizes its address within the message signals, it initiates a transmit operation by forcing the first control line to the predetermined state.