Patent ID: 8051220

Claim:
A process control system for communications in a process control network, the process control system having a plurality of field devices that are communicatively linked to an I/O bus segment, the process control system comprising: a process controller communicatively coupled to a communication bus and programmed to process messages published on the communication bus and to publish messages on the communication bus; a primary redundant input/output (I/O) device communicatively linked to the communication bus and to the I/O bus segment, the primary redundant I/O device coupled between the process controller and a field device, the primary redundant I/O device being programmed to perform self-diagnostics to determine whether a primary redundant I/O device fault exists on the primary redundant I/O device; and a secondary redundant input/output (I/O) device communicatively linked to the communication bus and to the I/O bus segment, the secondary redundant I/O device coupled in parallel with the primary redundant I/O device between the process controller and the field device and programmed to detect a primary redundant I/O device fault and to perform self-diagnostics to determine whether a secondary redundant device fault exists on the secondary redundant I/O device; wherein, the secondary redundant I/O device, upon detecting a primary redundant I/O device fault, publishes a primary redundant I/O device fault message on the communication bus; the process controller, responsive to the primary redundant I/O device fault message, publishes a primary redundant I/O device self diagnostic order on the bus; in responding to the primary redundant I/O device self-diagnostic order, the primary redundant I/O device performs the self-diagnostics and publishes the results of the self-diagnostics on the bus; and if the results of the self-diagnostics indicate a primary redundant I/O device fault, the process controller activates the secondary redundant I/O device and deactivates the primary redundant I/O device, else if the results of the self-diagnostics indicate that a primary redundant I/O device fault does not exist, the process controller publishes a secondary redundant I/O device self diagnostic order on the communication bus.