# Issue reading the individual bits within a 16 bit Word

**URL:** <https://forum.inductiveautomation.com/t/issue-reading-the-individual-bits-within-a-16-bit-word/16599>\
**Category:** Ignition\
**Created:** [January 15, 2018, 8:13pm UTC](https://forum.inductiveautomation.com/t/issue-reading-the-individual-bits-within-a-16-bit-word/16599 "2018-01-15T20:13:05Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![SMortensen](https://avatars.discourse-cdn.com/v4/letter/s/a183cd/32.png) [@SMortensen](https://forum.inductiveautomation.com/u/SMortensen)\
**Post date:** [January 15, 2018, 8:13pm UTC](https://forum.inductiveautomation.com/t/issue-reading-the-individual-bits-within-a-16-bit-word/16599/1 "2018-01-15T20:13:05Z")

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Can someone tell me what I am doing wrong? I am trying to read the individual bits within a 16 bit Word and assign each bit to a Tag. Each time I try, I end up with a “Config Error” in the Tag Diagnostics. Below is my setup:

* * *

OPC-UA Device/  
Name: AAA  
Type: Modbus TCP  
Description: Schneider Modicon Momentum PLC  
Enabled: True

Addresses/  
Prefix: 400  
Start: 401  
End: 402  
Step: False  
Unit ID: 0  
Modbus Type: Holding Resister (int16)  
Modbus Address: 401  
Radix: 10

* * *

## In Designer, I drag the desired tags from the OPC Browser to the Tag Browser. Then, open one of the created tags in the Tag Editor and edit it as shown below.

Tag Browser/  
Name: 400401 Bit 0  
Data Type: Boolean  
Enabled: Yes  
Access Rights: Read Only  
OPC Server: Ignition OPC-UA Server  
OPC Item Path: ns=1;s=[AAA]400401.0  
Source Data Type: Auto

Tag Diagnostics/  
Quality: Config Error

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<div class="post-metadata">

**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:** [January 15, 2018, 9:43pm UTC](https://forum.inductiveautomation.com/t/issue-reading-the-individual-bits-within-a-16-bit-word/16599/2 "2018-01-15T21:43:13Z")

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You are making one or two mistakes:

- Not all Modbus devices support bit-level accesses to holding registers. If so, you’ll have to bring in the whole word and fan it out into bits within Ignition.
- You cannot use the ‘4’ prefix. You need to use the ‘HR’ prefix instead.

See the [Modbus Addressing](https://docs.inductiveautomation.com/display/DOC79/Modbus+Addressing) page for the details.