# 25s interval time between plc tag value refresh

**URL:** <https://forum.inductiveautomation.com/t/25s-interval-time-between-plc-tag-value-refresh/80005>\
**Category:** Ignition\
**Created:** [October 4, 2023, 8:45am UTC](https://forum.inductiveautomation.com/t/25s-interval-time-between-plc-tag-value-refresh/80005 "2023-10-04T08:45:20Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![chaoliang](https://avatars.discourse-cdn.com/v4/letter/c/ba8739/32.png) [@chaoliang](https://forum.inductiveautomation.com/u/chaoliang)\
**Post date:** [October 4, 2023, 8:45am UTC](https://forum.inductiveautomation.com/t/25s-interval-time-between-plc-tag-value-refresh/80005/1 "2023-10-04T08:45:20Z")

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I have a site siemens 400 plc. it is.connected to a wonderware scada at the moment.

I set up an ignition local gateway taking only 10000 tags, but the refresh time is 25+ seconds.

if i remove the tags to only 500, the refresh time is 2 seconds as per designed in tag group.

what is the possible solutions I should try to improve the comms speed? most of the tags are configured to 5s scan time.  
It is a local ignition gateway with lan cable to the 400 plc.

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**Author:** ![chaoliang](https://avatars.discourse-cdn.com/v4/letter/c/ba8739/32.png) [@chaoliang](https://forum.inductiveautomation.com/u/chaoliang)\
**Post date:** [October 4, 2023, 9:04am UTC](https://forum.inductiveautomation.com/t/25s-interval-time-between-plc-tag-value-refresh/80005/2 "2023-10-04T09:04:54Z")

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there are 7349 tags in the gateway.  
overload:  
at 3584ms  
1102%

at 5020ms  
764%

at 7421ms  
401%

at 8401ms  
455%

Is it because simply the plc cannot handle the comms with two scada systems?  
never have such issue with 1500 or compactlogix or m340.

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**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\
**Post date:** [October 4, 2023, 11:06am UTC](https://forum.inductiveautomation.com/t/25s-interval-time-between-plc-tag-value-refresh/80005/3 "2023-10-04T11:06:04Z")

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> [@chaoliang](#):
>
> Is it because simply the plc cannot handle the comms with two scada systems?

That 's certainly what it looks like. Not surprising with such an old processor, I would think.

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**Author:** ![JordanCClark](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/jordancclark/32/83362_2.png) [@JordanCClark](https://forum.inductiveautomation.com/u/JordanCClark)\
**Post date:** [October 4, 2023, 11:07am UTC](https://forum.inductiveautomation.com/t/25s-interval-time-between-plc-tag-value-refresh/80005/4 "2023-10-04T11:07:33Z")

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I'm not a Siemens guy, but the S7-400 supports a 480 byte PDU, while Ignition's default size is 240. That would help a bit.

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<div class="post-metadata">

**Author:** ![chaoliang](https://avatars.discourse-cdn.com/v4/letter/c/ba8739/32.png) [@chaoliang](https://forum.inductiveautomation.com/u/chaoliang)\
**Post date:** [October 6, 2023, 10:01am UTC](https://forum.inductiveautomation.com/t/25s-interval-time-between-plc-tag-value-refresh/80005/5 "2023-10-06T10:01:40Z")

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Thank you for the hint.

I changed the value to 480 in the driver advance setting, the overloads are back to normal

Sampling time is around 4sec, which is acceptable to this project.