M172 modbus RTU function block

[quang21]

Hello everyone, I want to ask if I use a function block to read the modbus and use the EN input to activate that Function block to read that register. In case I have 20 devices, but the response time is slow, do I need to hold that EN input long enough to read back or just trigger it once like pulse type is enough

[Bastian_Schmitz · Accepted solution]

You need to call the function in the background task. If this function need a long time to proceed, the whole background task need this time. Regarding to this point. A change of the en input is only possible in the next task, and that is when the FC is finished. 

[quang21]

Thank you very much

[quang21]

Hi Bastian_Schmitz
Can i ask one more. how do i configure polling time for modbus using function block

[FedericoM]

Hi,

in case of messages with a polling time, I would consider to manage them from Configuration perspective.

In terms of Polling time for messages defined in background, I would implement them using a TON which will trigger the message send and the TON reset

[quang21]

Thanks You Verry Much