Programmable sequence controller and system

Abstract

A programmable sequence controller and a sequence control system including a plurality of such controllers. Each sequence controller includes a program memory for storing a preprogrammed sequence of instructions for controlling a machine or part of a machine in response to the status of the machine or part being controlled. Each controller includes data transfer circuitry for receiving status data from another sequence controller on a common data bus and transmitting its own status data to all of the other sequence controllers on the common data bus. Each sequence controller includes an input-output (I/O) memory and an (I/O) flag memory for storing and keeping track of current status information from each of the plurality of controllers. Thus, each controller can make a control decision based not only on input and output status data from the specific machine or machine part that it controls but also based on the status of the machines or machine parts being controlled by the other sequence controllers linked by the common data bus. The number of sequence controllers linked by the common data line can be increased as necessary to execute increasingly complex control functions.