Distributed industrial control system with remote stations taking turns supervising communications link between the remote stations

摘要

A control system for controlling an industrial process includes a plurality of remotely located process control units (remotes) each coupled to an associated input/output device(s) and adapted to communicate with one another through a dual channel communications link. Each remote has a unique succession number within a predetermined succession order with supervisory communication-control of the communication link sequentially transferred to each remote according to its succession number to provide a revolving or master for the moment control of the system. Each remote after completing its turn as master transmits a control block to the next remote in the sequence. Each remote, when exercising supervisory communication control of the communication link, may transmit data in block form to other remotes and request and receive data back from other remotes. Each remote upon completing its turn transmits a control block to the next remote in the sequence, which, upon receiving the control block, tests for validity and, if valid, transmits an acknowledgement signal to the remote which transmitted the control block. The next remote then takes its turn exercising supervisory control over the communications link and, in the same manner, the supervisory control is transferred from one remote to the next in the sequence.