# Quality of Modbus tags is "Good" on the server but "Uncertain\_InitialValue" on Ignition Designer Tag Browser **URL:** \ **Category:** Ignition\ **Created:** [June 24, 2025, 8:34pm UTC](https://forum.inductiveautomation.com/t/quality-of-modbus-tags-is-good-on-the-server-but-uncertain-initialvalue-on-ignition-designer-tag-browser/107737 "2025-06-24T20:34:43Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![Doemdz](https://avatars.discourse-cdn.com/v4/letter/d/dfb087/32.png) [@Doemdz](https://forum.inductiveautomation.com/u/Doemdz)\ **Post date:** [June 24, 2025, 8:34pm UTC](https://forum.inductiveautomation.com/t/quality-of-modbus-tags-is-good-on-the-server-but-uncertain-initialvalue-on-ignition-designer-tag-browser/107737/1 "2025-06-24T20:34:43Z")
Hi, I'm trying to set up a tag change script but I am having issues reading and writing to my Modbus coils on Designer. I can read and write to the Modbus coils just fine through the OPC Quick Client, but when I create an OPC tag and connect it to the Modbus register, I get "Uncertain\_InitialValue" under Quality. I have tags set up from other devices connected via TCP driver and those seem to be working just fine on Designer. Any ideas of what could be happening? ---
**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:** [June 24, 2025, 8:46pm UTC](https://forum.inductiveautomation.com/t/quality-of-modbus-tags-is-good-on-the-server-but-uncertain-initialvalue-on-ignition-designer-tag-browser/107737/2 "2025-06-24T20:46:43Z")
You mention both coils and registers. Not all devices can write to individual bits of holding registers (especially modern Schneider pieces of junk). Share more? ---
**Author:** ![Doemdz](https://avatars.discourse-cdn.com/v4/letter/d/dfb087/32.png) [@Doemdz](https://forum.inductiveautomation.com/u/Doemdz)\ **Post date:** [June 24, 2025, 8:58pm UTC](https://forum.inductiveautomation.com/t/quality-of-modbus-tags-is-good-on-the-server-but-uncertain-initialvalue-on-ignition-designer-tag-browser/107737/3 "2025-06-24T20:58:27Z")
I'm sorry, I didn't mean to say register. When I connect the OPC tag to the Modbus Coil I get the Uncertain\_initial Value. I am using a Sealevel eIO 110 modbus device. They seem to work fine on OPC Quick Client but can't create an OPC tag that I can read or write to ---
**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:** [June 24, 2025, 9:09pm UTC](https://forum.inductiveautomation.com/t/quality-of-modbus-tags-is-good-on-the-server-but-uncertain-initialvalue-on-ignition-designer-tag-browser/107737/4 "2025-06-24T21:09:02Z")
> [@Doemdz](#): > > seem to work fine on OPC Quick Client And you are confirming that the device's data matches what you read or wrote? > [@Doemdz](#): > > can't create an OPC tag that I can read or write to Makes me suspect other problems. Please share the manually addressed OPC Item Paths you are trying in your OPC tags. ---
**Author:** ![Doemdz](https://avatars.discourse-cdn.com/v4/letter/d/dfb087/32.png) [@Doemdz](https://forum.inductiveautomation.com/u/Doemdz)\ **Post date:** [June 24, 2025, 9:35pm UTC](https://forum.inductiveautomation.com/t/quality-of-modbus-tags-is-good-on-the-server-but-uncertain-initialvalue-on-ignition-designer-tag-browser/107737/5 "2025-06-24T21:35:40Z")
Yes I am just writing 1's and 0's to the tags. Let me share some screenshots ![test bit ss](https://us1.discourse-cdn.com/inductiveautomation/original/3X/6/3/631997e4cd8aacdaa0281805f0e35d90075d2af3.png) This is how I set up my OPC tag in Designer. ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/4/5/45b9f5f0aa8b32b38c7da1e0a8fe98addf9ff943.png) This is the screenshot of me reading the value of the modbus coil on ignition ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/6/6/66f4647426a5ce184781077688b9ecfbb2786e91.png) This is my address setup for the device ---
**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:** [June 24, 2025, 10:27pm UTC](https://forum.inductiveautomation.com/t/quality-of-modbus-tags-is-good-on-the-server-but-uncertain-initialvalue-on-ignition-designer-tag-browser/107737/6 "2025-06-24T22:27:15Z")
Leave out the `1.` when using mappings--they have the unit embedded in the symbol. (Better is to not use the mapping facility at all.) ---
**Author:** ![Doemdz](https://avatars.discourse-cdn.com/v4/letter/d/dfb087/32.png) [@Doemdz](https://forum.inductiveautomation.com/u/Doemdz)\ **Post date:** [June 25, 2025, 12:14pm UTC](https://forum.inductiveautomation.com/t/quality-of-modbus-tags-is-good-on-the-server-but-uncertain-initialvalue-on-ignition-designer-tag-browser/107737/7 "2025-06-25T12:14:33Z")
Do you mean leave out the 1 in the OPC item path? ---
**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:** [June 25, 2025, 12:17pm UTC](https://forum.inductiveautomation.com/t/quality-of-modbus-tags-is-good-on-the-server-but-uncertain-initialvalue-on-ignition-designer-tag-browser/107737/8 "2025-06-25T12:17:20Z")
And the dot. When you use mapping names, the unit number is included in the mapping, so it doesn't belong in the OPC Item Path. But anyway, make a tag with the manual address `[DD6]1.C1` in the OPC Item Path and see what you get. (Based on your examples, you may also need to adjust the device's advanced setting for "Zero-based Addressing".) ---
**Author:** ![Doemdz](https://avatars.discourse-cdn.com/v4/letter/d/dfb087/32.png) [@Doemdz](https://forum.inductiveautomation.com/u/Doemdz)\ **Post date:** [June 25, 2025, 1:00pm UTC](https://forum.inductiveautomation.com/t/quality-of-modbus-tags-is-good-on-the-server-but-uncertain-initialvalue-on-ignition-designer-tag-browser/107737/9 "2025-06-25T13:00:29Z")
I still get the same "Uncertain\_InitialValue" under Quality, and can't read/write to the tag. I have zero based addressing turned on and I know that is the correct setting. ---
**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:** [June 25, 2025, 1:04pm UTC](https://forum.inductiveautomation.com/t/quality-of-modbus-tags-is-good-on-the-server-but-uncertain-initialvalue-on-ignition-designer-tag-browser/107737/10 "2025-06-25T13:04:03Z")
Can you remove all of your address mappings and then edit/save the device? I think you may be running into a known bug with the address mapping page. Alternatively, create a new device instance, do not add an address map to it, and only create the direct address OPC Tag (`[device]1.C1` etc...). ---
**Author:** ![Doemdz](https://avatars.discourse-cdn.com/v4/letter/d/dfb087/32.png) [@Doemdz](https://forum.inductiveautomation.com/u/Doemdz)\ **Post date:** [June 25, 2025, 1:17pm UTC](https://forum.inductiveautomation.com/t/quality-of-modbus-tags-is-good-on-the-server-but-uncertain-initialvalue-on-ignition-designer-tag-browser/107737/11 "2025-06-25T13:17:28Z")
That didn't seem to change anything ---
**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:** [June 25, 2025, 1:18pm UTC](https://forum.inductiveautomation.com/t/quality-of-modbus-tags-is-good-on-the-server-but-uncertain-initialvalue-on-ignition-designer-tag-browser/107737/12 "2025-06-25T13:18:40Z")
Maybe time to give support a call. ---
**Author:** ![Doemdz](https://avatars.discourse-cdn.com/v4/letter/d/dfb087/32.png) [@Doemdz](https://forum.inductiveautomation.com/u/Doemdz)\ **Post date:** [June 25, 2025, 1:40pm UTC](https://forum.inductiveautomation.com/t/quality-of-modbus-tags-is-good-on-the-server-but-uncertain-initialvalue-on-ignition-designer-tag-browser/107737/13 "2025-06-25T13:40:17Z")
Thanks for the help ---
**Author:** ![drojas](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/drojas/32/3403_2.png) [@drojas](https://forum.inductiveautomation.com/u/drojas)\ **Post date:** [March 6, 2026, 9:38pm UTC](https://forum.inductiveautomation.com/t/quality-of-modbus-tags-is-good-on-the-server-but-uncertain-initialvalue-on-ignition-designer-tag-browser/107737/14 "2026-03-06T21:38:08Z")
Can you elaborate on this known bug? I just ran into the same thing. You’ll notice doing a “r” to read the tag on the quick client shows Value 114 and Quality Good. But “s” subscribing to the same tag shows the Uncertain\_InitialValue. I ended up removing all address mappings and used the C, HR, HRI, etc. in the OPC Item Path instead and it reads just fine. ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/0/1/0177a9fd71d976b1484b766371560a2a2be02d99.png) ---
**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:** [March 6, 2026, 10:47pm UTC](https://forum.inductiveautomation.com/t/quality-of-modbus-tags-is-good-on-the-server-but-uncertain-initialvalue-on-ignition-designer-tag-browser/107737/15 "2026-03-06T22:47:34Z")
The bug I was referring to is described in the issue tracker like this: > If you have at least one tag that uses an address mapping prefix, and remove that address mapping, then all other OPC tags pointing to the device receive Uncertain\_LastKnownValue quality. not sure if that is what you saw or not.