RS485 bus communication time sequence control method

Abstract

The invention relates to an RS485 bus communication time sequence control method which is characterized by comprising the following steps that: S1, a host initiates a query message, arranges and combines n slaves to be queried into a frame of message according to a serial number seq, and sends the frame of message to the slaves through a bus; S2, the slaves receive a query message; S3, the slavesset delay sending time tsend according to the seq serial number; S4, the slaves determine whether the waiting time is greater than the delay sending time tsend or not, and send a response message when the waiting time is greater than the delay sending time tsend; S5, the host receives a slave response message; S6, the host determines whether the current operation time t exceeds a set value twaitor not, if so, the host ends the query, and if not, the host returns to execute the step S5. According to the method, a one-question multi-answer query mode between the host and the slaves can be realized, and the communication efficiency is greatly improved.

Description

technical field [0001] The invention relates to the technical field of communication, in particular to a timing control method for RS485 bus communication. Background technique [0002] The RS485 bus is an interface standard developed from RS232. It is suitable for point-to-point, one-master-to-multiple-slave communication, which makes up for the interconnection problems of the RS232 interface standard, and has the advantages of simple interface, low cost, long communication distance and high reliability. Widely used in transportation, aviation, aerospace, automatic control and other fields. [0003] In the industrial field, the RS485 bus usually adopts a half-duplex communication method. A master and multiple slaves are mounted on the bus, and the slaves are not allowed to initiate data transmission. Usually, the working mode is that the master performs data transmission on the slaves mounted on the bus. A question-and-answer query to read data, and each device needs to be...

AI Technical Summary

Problems solved by technology

[0003] In the industrial field, the RS485 bus usually adopts a half-duplex communication method. A master and multiple slaves are mounted on the bus, and the slaves are not allowed to initiate data transmission. Usually, the working mode is that the master performs data transmission on the slaves mounted on the bus. A question-and-answer query to read data, and each device needs to be delayed when reading and writing switching, which leads to slower data update in a single cycle when there are many hardware modules connected to the same bus, which affects communication efficiency

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