# Modbus Address mapping vs Manually specifying address registers at the OPC Path

**URL:** <https://forum.inductiveautomation.com/t/modbus-address-mapping-vs-manually-specifying-address-registers-at-the-opc-path/110278>\
**Category:** Ignition\
**Created:** [August 29, 2025, 3:02pm UTC](https://forum.inductiveautomation.com/t/modbus-address-mapping-vs-manually-specifying-address-registers-at-the-opc-path/110278 "2025-08-29T15:02:01Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![pradeep.nadimpalli](https://avatars.discourse-cdn.com/v4/letter/p/6a8cbe/32.png) [@pradeep.nadimpalli](https://forum.inductiveautomation.com/u/pradeep.nadimpalli)\
**Post date:** [August 29, 2025, 3:02pm UTC](https://forum.inductiveautomation.com/t/modbus-address-mapping-vs-manually-specifying-address-registers-at-the-opc-path/110278/1 "2025-08-29T15:02:02Z")

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I have a device (MOXA Gateway) from which I’m subscribing to some tags. Due to non-software issues (long cable lengths, interference etc. - let’s say they won’t be fixed) the device doesn’t respond to all requests and I have an overload factor \>\> 100% when I scan all tags at 3s rate. I changed some tags to 5seconds scan rate and others to 10secs and that helped bring the OF down. Increasing the Concurrent connections to 2 also helped.  
However, some tags still report bad quality in some scans.

So I tried address mapping and that reduced the overload factor much more. So I’m wondering if address mapping is better for performance ?

The registers are quite spread out some requiring conversions to int32, some to float, some to unsigned int.

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**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\
**Post date:** [August 29, 2025, 3:08pm UTC](https://forum.inductiveautomation.com/t/modbus-address-mapping-vs-manually-specifying-address-registers-at-the-opc-path/110278/2 "2025-08-29T15:08:44Z")

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No, addressing mapping doesn't change performance at all.

If you're actually seeing any performance difference something else changed - how many tags, how many requests, whether they get grouped, etc...

Maybe you can look at Wireshark captures to figure it out.

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**Author:** ![nideyijuyidong](https://avatars.discourse-cdn.com/v4/letter/n/7cd45c/32.png) [@nideyijuyidong](https://forum.inductiveautomation.com/u/nideyijuyidong)\
**Post date:** [August 29, 2025, 3:17pm UTC](https://forum.inductiveautomation.com/t/modbus-address-mapping-vs-manually-specifying-address-registers-at-the-opc-path/110278/3 "2025-08-29T15:17:40Z")

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Is this related to Span Gaps?

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**Author:** ![pradeep.nadimpalli](https://avatars.discourse-cdn.com/v4/letter/p/6a8cbe/32.png) [@pradeep.nadimpalli](https://forum.inductiveautomation.com/u/pradeep.nadimpalli)\
**Post date:** [August 29, 2025, 3:53pm UTC](https://forum.inductiveautomation.com/t/modbus-address-mapping-vs-manually-specifying-address-registers-at-the-opc-path/110278/5 "2025-08-29T15:53:02Z")

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> [@pradeep.nadimpalli](#):
>
> Not exactly. I had span gaps turned off in both methods.  
> On that note, enabling span gaps reduces the number of requests and the OF but there are too many bad tags.

Not exactly. I had span gaps turned off in both methods.  
On that note, enabling span gaps reduces the number of requests and the OF but there are too many bad tags.