Backboard communication method

Abstract

The invention discloses a backboard communication method, is additionally equipped with a fault diagnosis mechanism, improves system reliability, intelligently processes faults, reduces the fault processing duration and has small influence on a system control period. According to the backboard communication method, backboard wires between a PLC main controller and expansion modules comprise communication wires, a query wire and a feedback wire, the communication wires are two difference communication wires, an electrical characteristic of the communication wires is an RS485, all the expansion modules are connected through the communication wires in a bus mode, the query wire and the feedback wire are respectively a single wire, an electrical characteristic is ground 3.3V, and the query wire and the feedback wire are connected in a daisy chain mode; according to the method, one query wire and one feedback wire are additionally arranged between two adjacent expansion modules, the two adjacent expansion modules are provided with an interaction mechanism through the two signal wires, a state of a back-stage expansion module is accessed by a front-stage expansion module through the query wire, and a self state of the back-stage expansion module is fed back to the front-stage expansion module through the feedback wire.

Description

technical field [0001] The invention belongs to the technical field of electronic circuits and industrial control, and in particular relates to a backplane communication method. Background technique [0002] Programmable controller, referred to as PLC (Programmable Logic Controller), refers to a new type of industrial control device based on computer technology. PLC is a type of programmable memory used for internal storage of programs, execution of user-oriented instructions such as logic operations, sequence control, timing, counting and arithmetic operations, and control of various functions through digital or analog input / output. type of machinery or production process. [0003] Such as figure 2 As shown, when the programmable logic controller is put into operation, its working process is generally divided into three stages, namely, input sampling, user program execution, and output refresh. The completion of the above three stages is called a scan cycle. During the e...

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Problems solved by technology

However, when the expansion module fails (such as hot reset), the communication timeout will occur in the backplane communication, and the communication time will fluctuate at this time (the waiting time for the communication timeout is much longer than the normal communication time); on the other hand, the PLC master will try to deal with the failure, Both of these situations will cause large jitter to the control cycle and affect the stability of the system operation.

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