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Basic question to the PLC cycle - Modbus Communication


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Just to get a better system understanding...

I assume, the the PLC cycle is the following:

-> Read inputs

-> Execute the ladder logic

-> Write outputs

I am interested in the following:

- Modbus slave request. Is this done at the end of a cycle or asynchronous to the logic execution? (Data consistency)
- Modbus master periodic/ aperiodic. Is this done at the end of a cycle or asynchronous to the logic execution? (Data consistency)
- HMI display. Are the displayed values updated at the end of a cycle or asynchronous to the logic execution? (Data consistency)

Thanks,

Daniel

 

 

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