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  1. alexsanchez
  2. PLCnext Engineer
  3. Friday, 09 October 2020

Our project uses Modbus TCP both as client and server (to two different devices). Client seems to work well.

However, when I add the Modbus_TCP_Server3 block to my existing project, I have to set the timeout to 2000 ms in order for it to work with few interruptions, but if the Modbus master writes something, most of the times there is a Time Out.

 

As an experiment to test if the CPU was overloaded, I removed all the other logic from my project and the result was the same: Time Outs.

 

As yet another experiment, I created an empty project, with just the Modbus Server block and this time it did not Time Out!

 

So there must be something on my original project that caused a delay on the Modbus_TCP_Server3 block, and even after deleting everything (I think) it remained.

 

How do I go about solving this issue?

 

Thanks

Martin PLCnext Team Accepted Answer Pending Moderation
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Hi Alex,

Do you see the same behaviour when using the latest versions of PLCnext Engineer, PLC firmware, and Modbus library?

If the behaviour does not occur with the latest version, which versions does this behaviour happen with?

~ Martin.

Phoenix Contact Electronics Headquarters - PLCnext Runtime Product Management and Support

alexsanchez Accepted Answer Pending Moderation
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Hi Martin,

 

Yes, I forgot to add this info.

PLCNextEngineer: 2020.3

PLC FW: 2020.3

Modbus TCP Library: Version 6.

 

Also, probably I posted this question on the wrong forum, feel free to move it.

 

Thanks.

Martin PLCnext Team Accepted Answer Pending Moderation
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Hi Alex,

(The PLCnext Engineer topic is the correct one in this case, since the problem appears in the PLCnext Engineer Function Block "Modbus_TCP_Server").

Does the same behaviour occurs with the latest version of firmware (2020.6.1) and Modbus TCP library (version 7)?

Regards,
Martin.

Phoenix Contact Electronics Headquarters - PLCnext Runtime Product Management and Support

  1. one week ago
  2. PLCnext Engineer
  3. # 3
alexsanchez Accepted Answer Pending Moderation
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Hi Martin,

 

We ugraded PLCNextEngineer and PLC FW to 2020.6, and the Modbus library to 7, but the result is the same, when trying to write a coil or a register, there is a Time-Out error.

 

What else can we do?

 

Thanks.

 

BTW: when we hover the pointer on the library it says Version: 1.4.16.0

 

 

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