| 摘要 |
PURPOSE: A field bus communication system is provided to classify a plurality of slave devices, installed in a main communication system, into a main slave device and sub slave devices, and to enable the main slave to perform an analysis and check function and the slave devices to perform an I/O function. CONSTITUTION: The system comprises a master device(10), a serial communication line(20), a main slave device(50) and a plurality of sub slave devices(60). An analysis circuit of the main slave device(50) is directly connected to the master device(10) via the serial communication line(20), decodes an ID and a control instruction of a corresponding slave device and transmits the decoded data to a CPU(54) of the main slave device(50). The CPU(54) determines if the transmitted ID is among the IDs of the sub slave devices controlled by itself. In the case that the transmitted is included among the IDs controlled by the CPU(54), the CPU(54) processes the control instruction, and outputs a serial data type control instruction via an I/O channel allocated at a corresponding sub slave device. Then the sub slave device converts the serial control instruction data into a parallel control instruction data, and outputs the parallel control instruction data to an external device.
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