Development and investigation of a high level token passing module for local communication networks

A high level token passing protocol was developed for process control and data acquisition systems consisting of several stations with local computing power, each performing specific tasks in the system. These stations are interconnected by the process being monitored and controlled, and communicate via a separate communication medium. Each station gets the right to access this medium by means of a token message. The high level token message is structured like all other messages transmitted via the communication medium. The distribution of the access right to all stations is described by the token passing protocol, performed by the M 6800 microprocessor. The microprocessor based device interfacing the input/output port of a host computer to the communication medium is described.