I am Using M580 PLC & Citect 2018 Scada. Between PLC & SCADA communication is taking Place on MODNET. I am facing a problem of Slow update of tags on runtime hmi. In that case I would also like to mention that I have observed tag is updating its value immediately when I update its value from scada. But in opposite case if tag value is changed in PLC side it is taking more than 10 second to update on same hmi runtime. Please suggest ???
When you perform the control action from Citect, Citect writes this tag 'immediately' (at the soonest possible time) and doesn't wait for a general scan to occur.
However when you are updating the variable in the PLC, then Citect will only recognise and update this when it next scans the tag. I assume that this scanning is only occurring every 10 seconds.
So you should check what your scan rate is set to (and consult the driver documentation).
If your end device, and network, and driver can support a faster scan rate, and you do indeed need this faster update frequency, then you could change the Citect config to poll the device quicker.
Thanks for replying.
I have tried with some changes in ini file. can you please suggest what are the setting I have to check in citect config to faster polling of device.
Communication performance, and the performance to the operator screen is influenced by multiple factors:
- Client refresh rate (default is 250 mS)
- Driver used (modnet)
- Driver type setting (Modnet, Modnet, Modnet, see documentation)
- Network bandwith (100Mb ethernet?)
- Number of variables communicated continuously (?)
- PLC used (M580 CPU type)
- CPU scan time (unknown)
- Other devices communicating with the same CPU (?)
When taking only the driver into consideration and you're using Modnet, check the [Modnet] maxpending and maxoutstanding parameters. For example set the maxpending to 8 and maxoutstanding to 8 or higher (16);
Check the information in the driver documentation or in:
Also you might consider to use OFS instead of Modnet. For new applications, OFS is easier to use in combination with M580 CPU's.
@RoozeeR Kindly note the details as following:
- Client refresh rate (default is 250 mS)- If it is page scan time then it is 250mS
- Driver used (modnet)
- Driver type setting (Modnet, Modnet, Modnet, see documentation) - here MODNET 30
- Network bandwidth (100Mb ethernet?) - 1GB
- Number of variables communicated continuously (?)- Approx. 10K
- PLC used (M580 CPU type)- BME H58 2040 02.70
- CPU scan time (unknown)- 77mS
- Other devices communicating with the same CPU (?)- 2nos HMI Server, CPU 580-2 Safety PLC, 1 PRM with 8nos Profibus Node, 1 OPC Server
Also set maxpending to 8 and maxoutstanding to 8 , but problem remains. Please suggests.
According to your settings your application is limited in several ways. Most important: Modnet30 limits block read size to max. 64 words (see https://softwaresupportsp.aveva.com/#/okmimarticle/docid/tn8313)
Better to use OFS driver (OPC Factory Server) in combination with M580. For standard Modbus request, the block size is 125 registers and when max message length can be 1024 bytes (instead of 128 for standard Modnet30), thus decreasing the total amount of messages and increasing the performance.
OFS can also help optimizing the number of messages, specially when variable addresses are not in contiguous addresses.
As the max. number of messages processed per CPU cycle is limited, decreasing the max. number of messages will help, or increase the number of messages dedicated to Citect. The last is limited by CPU type.
In your 10K variables (if all %MW) could mean at least 10000/64= 156 messages. 8 per CPU cycle handled means 156/8= 20 CPU cycles (at least) to read them all. This means at least an update time of 20*77= 1.5 seconds (at least). But as you also have other communications, this number is the best case scenario.
Please read the TVDA "How Can I …Optimize OFS and Modicon M580 Ethernet Client/Server Performance?"
If you do not have this document, please contact your local Schneider Electric support organization. They can also support you to increase the overall performance.
When you perform the control action from Citect,
Other Citect.INI settings for the MODNET (both the generic driver, and port specific) should be left at their defaults (unless required specifically for successful communications)
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