The messaging service makes it possible to perform inter-PLC data exchanges using communication functions.
Two types of messaging are used:
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Private: UNI-TE on Modicon Premium and Telemecanique installed base,
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Standard: Modbus on Modicon Quantum, Modicon Premium, Modicon M340, Modicon M580, and Modicon Momentum installed base.
The destination entities of an exchange can either be located in a local station or in a remote station on a communication channel or directly in the CPU.
The communication functions provide an interface that is independent of the location of the destination entity. Furthermore, they mask the coding of the communication requests from the user. They thus provide compatibility of communication between Premium, Micro, Quantum, TSX 40, TSX 17, 1000 series and Modicon M340 PLCs.
NOTE: Processing of communication functions is asynchronous in relation to the processing of the application task which allowed them to be activated. The send/receive telegram and stop operation functions are the only exceptions as their execution is synchronous with the execution of the activation task.
Synchronous/Asynchronous Communication
A communication function is said to be synchronous when it is wholly executed during the PLC task that activated it.
A communication function is said to be asynchronous when it is executed during one or more PLC tasks after the task that activated it.
