Multi-request processing method for Modbus serial port communication of programmable controller

Abstract

The invention relates to a multi-request processing method for Modbus serial port communication of a programmable controller, which adopts a multi-request data reading function block and a multi-request data writing function block, supports a programmable controller CPU (Central Processing Unit) integrated serial port, and provides a multi-request data reading function block and a multi-request data writing function block for communication processing of a communication module and a serial port gateway through an Ethernet module. And processing of bit and word type data is supported. According to the method, the problems that the MODBUS can only initiate one request to one slave station at each moment, and request scheduling exists when a plurality of requests need to be initiated on the same bus are effectively solved; according to the method, the problem that programming of a read / write function block needs to be written for each request is tedious and complex is solved, and the problem that when a time-sharing mode is adopted or not adopted to schedule the requests, communication timeout and termination or a data updating period is long frequently is solved; the problem that normal reading and writing of data of other slave stations are affected when a certain slave station on a communication line is abnormal is completely eradicated.

Description

technical field [0001] The invention relates to the technical field of Modbus serial port communication of programmable controllers, in particular to a multi-request processing method for Modbus serial port communication of programmable controllers. Background technique [0002] When the communication module of the programmable controller is applied, one or two channels of the communication module are used as the Modbus master station, and often connect multiple slave stations or multiple read and write data requests. First, because the Modbus bus can only initiate one request to a slave station at each moment, and when multiple requests need to be initiated on the same bus, there will be a problem of orderly and efficient scheduling of each request; second, Under normal circumstances, it is often necessary to write a read / write function block for a request, which causes cumbersome and complicated programming problems; third, use or not use a time-sharing method to schedule ...

AI Technical Summary

Problems solved by technology

First, because the Modbus bus can only initiate one request to a slave station at each moment, and when multiple requests need to be initiated on the same bus, there will be a problem of orderly and efficient scheduling of each request; second, Under normal circumstances, it is often necessary to write a read / write function block for a request, which causes cumbersome and complicated programming problems; third, use or not use a time-sharing method to schedule requests, which is often used in practical applications. Problems such as communication timeout, communication termination or long data update cycle will occur; Fourth, if there is an abnormality in a certain slave station device on the communication line, it will affect the normal reading and writing of data of other slave stations

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