| 摘要 |
PURPOSE: An expansion system of a programmable logic controller by a serial transmission and a method for operating the same are provided to easily expand the base by connecting the local base having PLC central process unit to the expansion base through the local Ethernet. CONSTITUTION: An expansion system of a programmable logic controller by a serial transmission includes a plurality of expansion bases(230), a local base(200) and a serial transmission line(250). Each of the expansion bases(230) is provided with a bus expansion unit(231) and an input/output device(233). The bus expansion unit(231) transmits the operational state of the input/output device(233) to the local base(200) by controlling the input/output device(233) appended thereto in response to the control command from the local base(200). The input/output device(233) performs the operation in response to the control command received from the bus expansion unit(231). The local base(200) is provided with a central process unit(203) and a bus central unit(201). The central process unit(203) has the operational OS of the programmable logic controller(PLC) and the control command program in response to the operational state of the input/output device(233). And, the bus central unit(201) transmits the control command to the bus expansion unit(231) in the expansion base(230) through the serial transmission line(250).
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