# Connecting with Modbus, Tag Issues

**URL:** <https://forum.inductiveautomation.com/t/connecting-with-modbus-tag-issues/18393>\
**Category:** Ignition\
**Created:** [June 11, 2018, 1:47pm UTC](https://forum.inductiveautomation.com/t/connecting-with-modbus-tag-issues/18393 "2018-06-11T13:47:58Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![harryzhou4498](https://avatars.discourse-cdn.com/v4/letter/h/71c47a/32.png) [@harryzhou4498](https://forum.inductiveautomation.com/u/harryzhou4498)\
**Post date:** [June 11, 2018, 1:47pm UTC](https://forum.inductiveautomation.com/t/connecting-with-modbus-tag-issues/18393/1 "2018-06-11T13:47:58Z")

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I’m having issues connecting Modbus properly to the Ignition server. My tags either display unknown quality or not connected and NULL for value in the Tag Diagnostics tab, but on Ignition, it states that my Modbus device connection should be fine. I’m not sure if its an issue with my tag path or with my registry values or with my connection.

 ![](https://us1.discourse-cdn.com/inductiveautomation/original/2X/4/4639b78a5e150f9751435f666e72a11dab82215d.PNG) ![](https://us1.discourse-cdn.com/inductiveautomation/original/2X/6/6d195680e6fe832bffa72292e0a96ea64fb99005.PNG) ![](https://us1.discourse-cdn.com/inductiveautomation/original/2X/7/7d5f2c283703c7cf1847923c2dca39e5ed9ac634.PNG)  
I’m also getting this error in my logs: ![](https://us1.discourse-cdn.com/inductiveautomation/original/2X/4/48c19e7cf3708c4d9be506b06d99f7b48e65f7ac.PNG) ![](https://us1.discourse-cdn.com/inductiveautomation/original/2X/1/15714e46580f8fd7e54870b930986daf68320082.PNG)  
A device manual is here: [Modbus Connection And Control - Ingersoll-Rand Xe-145M Instruction Manual [Page 53] | ManualsLib](https://www.manualslib.com/manual/1239850/Ingersoll-Rand-Xe-145m.html?page=53)

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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:** [June 11, 2018, 2:27pm UTC](https://forum.inductiveautomation.com/t/connecting-with-modbus-tag-issues/18393/2 "2018-06-11T14:27:53Z")

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Why do you have a period before the rest of your address? That’s only necessary when specifying the unit/slave ID along with it: `[Modbus]0.HR0`, etc…

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<div class="post-metadata">

**Author:** ![harryzhou4498](https://avatars.discourse-cdn.com/v4/letter/h/71c47a/32.png) [@harryzhou4498](https://forum.inductiveautomation.com/u/harryzhou4498)\
**Post date:** [June 11, 2018, 2:39pm UTC](https://forum.inductiveautomation.com/t/connecting-with-modbus-tag-issues/18393/3 "2018-06-11T14:39:04Z")

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Sorry about that, I tried experimenting with 1.HR0, 2.HR0 since I wasn’t sure if I had a specified unit ID but I forgot to get rid of the period. I’m still getting a similar issue though.

 ![](https://us1.discourse-cdn.com/inductiveautomation/original/2X/e/e4d67c593647e2ba07ba68a24ef167e3828be774.PNG)

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<div class="post-metadata">

**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 11, 2018, 2:50pm UTC](https://forum.inductiveautomation.com/t/connecting-with-modbus-tag-issues/18393/4 "2018-06-11T14:50:40Z")

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It seems from the error you posted the device simply isn’t responding. After 3 consecutive timeouts the driver reconnects (this is a setting you can enable/disable).

People usually see this when the device they’re connected to isn’t configured correctly or doesn’t have the registers mapped, or has the registers mapped to different addresses than they think.