M580 M340 Communication Error

[SebahattinGundem55]

There is a system created with M580 plc and CRA modules.

Service ports are connected to equipment operating with HMI and Modbus TCP IP.

The communication of modbus devices is constantly interrupted.
Reading and writing operations were done with the io scanning and read_var, writer_var commands.

Why does this problem occur?

[Ricard]

Hello @SebahattinGundem55 ,

In order to help you, we will need a little more information, system versions, firmware, Control Expert, network architecture, but where you can really see what is happening is by analyzing the frames between the CPU and the other devices.

As I always say... The truth is there inside!!! 😉

With the frames you will see how the different devices are connected and if the loss of communication is due to timeout, or invalid Function code. However, this information is also provided to you by the explicit communication blocks.

Best regards

Ricard

[SebahattinGundem55]

Hello Richard,
First of all thank you for your return.

I use the Control Expert Classic v15.2 and you can find the system topology in the attachment.

BR

Sebahattin

[MetinSakin]

First of all you can not use Unmanaged switch in CRA ring ( RSTP protocol needed) 

This can cause a loop in all network .

Also 

Also please provide more info about the devices connected to CRA service port what kind of switch do you use there? is there any ring at that topology ? PAS 600 supports ring bur CRA service port does not support that so you should not create any kind of ring there 

[SebahattinGundem55]

The connection of the service port of the cra module is in the attachment.

[Ricard]

Hello @SebahattinGundem55 ,

Just as @MetinSakin tells us, you need to check the Ethernet architecture, there are some issues to resolve. For example iRIO ring or how the different DIO communications are connected to system, on this point I don't see clear the architecture. Probably you have a more detailed drawing, where you show the ports connected and the IP address. 

On the other hand, about the communications to M340, I advise you to check the IP address you configure to communicate to M580, because in this architecture (if you don't have the NOC connected to the backplane) you need to communicate with the NOC, not with the M580 CPU.

Good luck!

Ricard