Industrial control systems having input/output circuits with programmable input/output characteristics

Abstract

A programmable analog I/O circuit for use in an industrial control system has a first mode of operation as an input circuit and a second mode of operation as an output circuit. In the first mode of operation, a device-side I/O terminal is adapted for receiving an analog input status signal from an analog input device. In the second mode of operation, the device-side I/O terminal is adapted for transmitting an analog output control signal to an analog output device. According to another aspect, a programmable I/O circuit that drives an output device in an industrial control system comprises a plurality of configurable gain stages and a plurality of programmable isolating links. The plurality of programmable isolating links are coupled to the plurality of configurable gain stages and are programmable to determine a series or parallel arrangement of the plurality of configurable gain stages. The output control signal produced by the parallel arrangement is a high current, low voltage output signal as compared to the output control signal produced by the series arrangement. According to another aspect, an integrated circuit fabricated on a single semiconductor chip comprises an I/O interface, a control/logic circuit, and a communication interface. The integrated circuit may be advantageously used to provide a highly distributed industrial control system in which control is distributed all the way to the device level.