I was wondering what the best practice is for two-way communication between two Wago’s would be? I’m looking into splitting the PLC- and the HMI-program in two separate PLC’s and would need lots of variables with R/W access. A Modbus TCP-slave on the PLC?

Use Codesys NVL lists to share data between PLCs. Anssi

Yes, I’ve tought about that and have been using NVL, but it’s limited in size and not two-way (as per file)

Ok, NVL is usefull for process live data exchange. For parameterizing, Modbus can be suitable. As I can remember, also Modbus write multiple registers is limited. Also CANOpen SDO is for suitable for parameterizing system if CAN bus in use. How much data bytes included in your “block”? Binary …

Regarding the Modbus I’ve made a “protocol” which compares structures and write changes but it is kind of heavy and was hoping for a simpler solution. Well, it’s arrays of data structures so it would be a NVL list per object (considering the size of the structure). I’ve not used the FTP-FB - not s…

If your array member fits to one NVL list, try to make a list as follows nArrayIndex : int ; // Array index stcObject : MyDataSetObject ; Set array index and copy your member object in to stcObject. Activate event trigger variable to send NVL list to others. In receiver side. Copy data from NVL…

Since Firmware 24 you can use OPC UA to Exchange Data between PLC‘s For the HMI / Touchpanels TP600, the OPC Functions are available since FW25. (Visu-Panel and Control Panel) The Release of FW26 will Include the possiblily to use the Datasource Manager with option „CodesysV3Application“ up to now…

I tried exchanging some data between two PFC200s with OPCUA but after getting all the symbols on 2nd PFC from 1st PFC (online), there was no live data and all variables with default values (0). Couldn’t figure it out so I just used NV. Fortunatelly it was sufficient for this case. But it’d be great …

Hi, old topic but a question popped up. Do you know if there is a limit in the number of variables in a NVL? I found in CS3.5 docs that the size of each variable cannot exceed 255 bytes, but nothing on the list itself - other than If the size of the GVL exceeds the maximum length of the network …

I think it depend on your GVL configuration. If you use the option “Pack the variables” you need a list which is less than 256 Bytes (MAX 255). If you don’t use the option, each variables need to be less than 256 Bytes. But I’ve haven’t heard about a limitation yet.

Best solution for two-way communication

CODESYS

bjornidar September 13, 2023, 9:35am 7

Sounds like a feasable solution, thanks!
I will give it a try

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Best solution for two-way communication

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