A shadow function block interface for use in a process control network

摘要

A process controller that is communicatively coupled to an external field device via a communication network uses a shadow function block 108 disposed within a process controller 12 to enable implementation of a control routine that uses both an internal function block 152 disposed within the process controller 12 and an external function block 112 disposed within the external field device 48. The shadow function block 108 includes a communication port that communicates with the external function block 112 via the communication network (and possibly an interface card 40) to thereby receive data pertaining to the external function block, a memory 156 that stores the received data according to a configuration protocol of the internal function block 152 and an output that provides the stored external function block data to the internal function block according to the configuration protocol of the internal function block. The communication port of the interface function block may include an output that sends data generated by the controller or the internal function block to the external function block using the communication protocol (e.g. Fieldbus) associated with the external function block.