11/30/2019 3:02 PM | |
Joined: 12/8/2014 Last visit: 9/23/2023 Posts: 7 Rating: (0) |
I am not sure if this blog still open, but I have a general question on Modbus FC3 and FC4. Modbus client gets an analog value using either FC3 or FC4, when TCPIP communications are sniffed, FC3 sequence goes: Query->Ack->Response->Ack, but for FC4 is: Query->Response->Ack, in RTU is very similar, in FC3 after Query, it returns same values, so, what is the advantage of FC3 or FC4?, how in Modbus server registers for FC3 are configured compare with FC4? ------------------------------------------------------------------------------------------ |
Last edited by: Jen_Moderator at: 12/02/2019 06:17:19New subject after splitting |
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12/10/2019 4:46 PM | |
Joined: 9/27/2006 Last visit: 10/5/2024 Posts: 12283 Rating: (2685) |
Hello Taji2310; Just one point: UDP does not require acknowledgements of data packets, so Modbus UDP would be faster, if less secure, than Modbus TCP. I have seen it discussed over the years in various automation sites, and some code has been published in opensource sites (sourceforge, for one); for example: Modbus TCP vs UDP; Modbus TCP vs RTU over RS-485 But I have never seen Modbus UDP used in an industrial environment. Hope this helps, Daniel Chartier |
Last edited by: dchartier at: 12/11/2019 03:38:00 |
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