Issue reading the individual bits within a 16 bit Word

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

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

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 page for the details.