# Ignition Tags form a modbus device in Uncertain\_LastKnownValue **URL:** \ **Category:** Ignition\ **Created:** [July 11, 2023, 11:35am UTC](https://forum.inductiveautomation.com/t/ignition-tags-form-a-modbus-device-in-uncertain-lastknownvalue/76184 "2023-07-11T11:35:49Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![Emile\_Laplante](https://avatars.discourse-cdn.com/v4/letter/e/c57346/32.png) [@Emile\_Laplante](https://forum.inductiveautomation.com/u/Emile_Laplante)\ **Post date:** [July 11, 2023, 11:35am UTC](https://forum.inductiveautomation.com/t/ignition-tags-form-a-modbus-device-in-uncertain-lastknownvalue/76184/1 "2023-07-11T11:35:49Z")
Hi, I created a modbus device. I filled the adresses. I Can read and write to the adresses through OPC quick client : ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/1/e/1e0044fdec3140f5903429ab808fb1e423fcedfe.png) But I keep getting the Uncertain\_LastKnownValue overlay on the designer : ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/3/9/39ab9b7581764edaa5a9b64797cfb8105c11bf00.png) ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/c/c/ccbeb4c7fbb539247b6a3442083e32b50b22bb2b.png) What can be the issue? ---
**Author:** ![Joe\_Seph](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/joe_seph/32/40277_2.png) [@Joe\_Seph](https://forum.inductiveautomation.com/u/Joe_Seph)\ **Post date:** [July 17, 2023, 10:37pm UTC](https://forum.inductiveautomation.com/t/ignition-tags-form-a-modbus-device-in-uncertain-lastknownvalue/76184/2 "2023-07-17T22:37:33Z")
Hi Emile, If you could provide some more details this will help the community better assist you; What version of Ignition are you currently using? Do you ever see values in the designer or are they always uncertain? Do you see any errors in your logs regarding Modbus or the OPC server? Have you tried restarting the OPC module?