System and method for distinguishing a device failure from an inter-device communication failure

A real-time process control system, comprising:

• a primary controller that controls said system;
• a secondary controller that assumes control of said system upon failure of said primary controller;
• a communication channel coupling said primary and secondary controllers that allows said primary and secondary controllers to communicate;
• and
• a circuit for distinguishing a failure of said primary controller from a failure of said communication channel, including:
• a device failure signal generator, associated with and separately powered from said primary controller, that communicates a device failure signal to said secondary controller upon occurrence of a predetermined condition, and
• a device failure signal detector, associated with said secondary controller, that detects said device failure signal, detection of said device failure signal contraindicating a failure of said communication channel and prompting said secondary controller to assume said control of said system.