Abstract: A plant management system is provided. The system includes one or more digital process control and data acquisition subsystems and a plant control network. Each control subsystem includes a data highway, and process control, and process interface units. The plant control network is a token-passing distributed plant control network in which a plurality of physical modules communicate with one another over a plant control bus. While there are limited number of different types with each type having different functions, all physical modules have common units, one of which is a module central processor unit. Both the number of modules and the number of types of modules of a plant control network have both a maximum and a minimum. Reliability of the plant management system is improved by a provision for redundancy at the physical module level. One type of physical module provides data communication and translation facilities between the plant control network bus and the data highway of a control subsystem.