Communication system using time division multiplex signal transmission

Abstract

A multiplex communication system in which operational data is transmitted to a bus line at different frequencies according to the necessity of transmission. Further, transmitting and receiving nodes are identified without having to include address data with the transmitted message data, thereby avoiding a time lag in control processing of vehicle-mounted equipment. In accordance with a first embodiment, a plurality of data signals which are transmitted via a bus line from a plurality of node devices, to at least one of a plurality of end node devices to be controlled, are divided into a plurality of degrees according to the necessity of transmission. Operational date signals falling into the greatest degree of transmission necessity are transmitted once in every cycle, while data signals falling into the lesser degrees of transmission necessity are transmitted once in every few cycles according to the degree of necessity. In a second embodiment, one of a plurality of node devices connected to a bus line serves as a master node device and sets the transmission cycle of message data transmitted onto the bus line. This cycle is set so as not to cause a time lag in data processing executed by the respective node devices. Each time interval between the start pulses is divided into a plurality of time slots. The time slots have been allocated to the individual node devices so that message data can be transmitted from the respective devices in the associated time slots.