3. PLC/terminal communication dialog cycle
Optimization for communication
NOTE
The following recommendations enable terminal/PLC communications to be optimized, thus improving operator dialog response times. They apply, regardless of the communication protocol used.
- make a careful allocation of the variables to single, cyclic or permanent reading, according to how they are used by the terminal,
- use contiguous addresses for the cyclic reading of variables on a page,
- use contiguous addresses for the single reading of variables on a page,
- do not overload the dialog table with words not needed by the application,
- adjust the dialog table period according to the traffic generated by the dialog application on the one hand and the other equipment items of the control system structure on the other hand.
The operator actions are processed immediately, independent of the value of the dialog table period.
A very short dialogue cycle can slow down :
- variables refresh,
- new page display.
As a rule, only the words which are useful for the application should be selected to optimize communication.
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Graphic Magelis
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