A process controller that is communicatively coupled to an external field device via a communication network uses a shadow function block disposed within a process controller to enable implementation of a control routine that uses both an internal function block disposed within the process controller and an external function block disposed within the external field device. The shadow function block includes a communication port that communicates with the external function block via the communication network to thereby receive data pertaining to the external function block, a memory that stores the received data according to a configuration protocol of the internal function block 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 associated with the external function block.