Plant controller simulator with structure for combining simuation signals with actual process I/O signals

摘要

A simulator apparatus for simulating a plant controller is connected to a process input/output circuit via a data bus, and via stations connected to the data bus. The actual plant controller is also connected to the same data bus via another of said stations, and can thereby receive signals from either the plant controller or the simulator, indiscriminately. Individual stations include input and output buffer registers and buffer memories, and an output OR circuit may be connected between the input and output registers.