Abstract: The present invention is a block oriented control system that allows interoperability between devices made by different manufacturers. A block oriented control system is a system which includes a plurality of field devices incorporating a physical layer, communication stack, and user layer, with the field devices being connected by a transmission medium, such as a bus. The physical layer receives signals from the bus and translates the signals into a message for the communications stack, and receives messages from the communications stack and translates the messages into signals for the bus. The communication stack controls the communications between devices operating in the control system. The user layer is a block oriented approach to the system's control functions, and includes function blocks and system management. The function blocks are standardized encapsulations of control functions, such as analog input or proportional/derivative.