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A
Andritz Feed and Biofuel3-Newcomer
3-Newcomer
June 4, 2026
Question

Kepware slowly updating values from Modbus TCP/IP (Modicon M580 PLC)

  • June 4, 2026
  • 1 reply
  • 30 views

Hello, i’m facing an issue with KepserverEX6 not updating values according to specified scan rate (1000ms)  from a Modicon M580 PLC. Modbus TCP/IP driver is set, i’m using 241 tags, i use only one channel and one device. Instead of 1s i see values update roughly 5-15 seconds.

 

There are no other clients in Kepware communicating to the same device, only one OPC UA client reads/writes the same data from localhost (soft-PLC installed in the same server where Kepware is). The same soft-PLC in parallel reads/writes data in a different channel (Simulator Driver), and there everything is okay. So i don’t think issue is coming from the soft-PLC.

 

When i use quick client on the Modbus TCP/IP channel i also see data updating slow.

Network card is 1gbit. 

 

My channel settings that could affect the communication are following:

Write Optimization :

Write only latest value for all tags

Duty Cycle is set to 10

Communication Serialization :

Network Mode is Load Balanced

Ethernet Socket utilization is set One or More Sockets per Device

 

My device settings that could affect the communication are following: 

Scan Mode:

Initially i set it to Respect Client Specified Scan Rate, but i’ve modified it to Respect Client- Specified Scan Rate since it seems slightly more faster.

Initial Updates from Cache are disabled.

 

Timing:

Connect Timeout is 3 s

Request Timeout is 1000ms

Attempts before timeout are 3

Inter-Request Delay is 0

 

Block Sizes:

Output Coils 32, Input Coils 32

Internal Registers 32, Holding Registers 32

Block Read Strings is Disable

 

I’ve read your Optimizing V6 Projects manual, and the specified articles about what could solve this issue, but i didn’t manage to do solve it. Could you assist me with advice on how to solve this problem and what settings could i change to improve it?

 

1 reply

A
Andritz Feed and Biofuel3-NewcomerAuthor
3-Newcomer
June 5, 2026

I’ve tried also increasing block sizes to 120 for IR and HR, 240 for OC and IC, reduced the  request timeout to 600ms, attempts before timeout to 1, i’ve set the scan mode to request data no faster than the scan rate (1000ms).  Data in the HR modbus registers is mostly grouped consistently in range of 100- 1200. This managed to bring down the time to 4-6 second of lag. 

I also noticed in diagnostic that driver is sending  tx and recieves two rx responses in roughly 100ms, i guess this means the PLC is responding quite fast and network is not the issue. But also what i see is alot of tx/rx requests in a single second. This is how the diagnostic is looking. I have no errors but still have late data, but less than what i started with. 

 

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