SiePortal

The integrated platform for your product selection, buying and support workflow - bringing together Industry Mall and Online Support.

Products & Services
- Menu temporary not available
- Menue temporary not available
- {{item.title}}
Support Support
{{(apiData.Support | filter:{'rank':1}:true)[0].title}} Support
- Menu temporary not available
- Menue temporary not available
- {{item.title}}
MySiePortal MySiePortal
{{(apiData.MySiePortal | filter:{'rank':1}:true)[0].title}} MySiePortal
- Menu temporary not available
- Menue temporary not available
- {{item.title}}
Cart ({{apiData.CartCount}})

Navigation

PLC intermittently misses "Write" operations from Kepware.

4/14/2025 7:37 AM	Rate (0)
AutoGen_2443258 Member Joined: 2/3/2022 Last visit: 5/27/2025 Posts: 2 Rating: (0)	I’m experiencing an intermittent issue with a Siemens S7-1500 (ET200pro) PLC communicating with Kepware via the S7 protocol. The PLC sets a tag `PLCCOM = 1`, which MES resets to `0` via Kepware. Occasionally—on 2 out of 30 identical stations—the PLC doesn’t seem to detect the reset, even though Wireshark shows the write command is sent and acknowledged. I’ve been troubleshooting this and noticed that Kepware polls data every 10ms, generating around 7kB of traffic within 100ms. PLC scan times are typically 19ms but can spike up to 90ms. I suspect that under high read load, the write may be delayed or even overwritten before the PLC logic processes it. Could this be related to communication buffer size or write requests being deprioritized in the PLC? Is there any documentation available on the S7-1500 or ET200pro buffer behavior and capacity?
	Last edited by: AutoGen_2443258 at: 04/14/2025 07:39:06 Last edited by: AutoGen_2443258 at: 04/14/2025 07:42:42 Last edited by: AutoGen_2443258 at: 04/14/2025 07:43:06
Suggestion To thank Quote Answer

4/16/2025 11:24 AM	Rate (0)
Murof Platinum Member Joined: 8/3/2009 Last visit: 9/5/2025 Posts: 16348 Rating: (1931)	Hello AutoGen_2443258 Do you write to a global DB or to a Instance DB? If you use the s7 communicatino like an old HMI then it could be that there are some kind of overwriting: https://support.industry.siemens.com/cs/de/en/view/109478253 you also have to check if you do not use In/Out parameters: https://support.industry.siemens.com/cs/de/en/view/109476062 Bye Murof
	If this Information really helps, you could use the Rate function
Suggestion To thank Quote Answer

4/17/2025 3:59 PM	Rate (0)
AutoGen_2443258 Member Joined: 2/3/2022 Last visit: 5/27/2025 Posts: 2 Rating: (0)	Hi Murof, Thank you for your comprehensive response. Although the DB used is Global DB, it is utilized as an InOut element. Based on what you have mentioned, I believe this could have an impact. Below is a representation of how FBs are called.

Suggestion To thank Quote Answer

Share this page:

Share this page on...