Allen-Bradley PLC/SLC syntax for Boolean tags

This is probably a foolishly simple question but I’m an absolute beginner with Ignition so I’ll go ahead and ask. I did what I thought was due diligence in the User Manual and Online Help.

What is the proper syntax in the Ignition SQLTags editor and OPC-UA driver for reading a single Bit from a Word-type register in a PLC-5, SLC, or MicroLogix controller ?

In RSLogix, this would be “B3:1/2” or “N7:3/4”, where the colon prefaces the Word number and the slash prefaces the Bit number.

I’m just starting with Ignition so I am connected to the SLC-500 Emulator with the OPC-UA driver with Ignition 7.2.5 (b26) running on Ubuntu 10.04.

The SQLTags browser lets me browse as far as the “B3:0” word but doesn’t browse for bits. I can manually add “/1” or “.1” to the tag address but this causes Bad Quality so it’s obviously not right.

I’ve also had a lot of timeouts in the OPC Tag Browser during my evaluation, so I’m certainly willing to chalk this up to the SLC500 OPC emulator data source, but I’m going to be using both SLC/MicroLogix and ControlLogix as my data sources in real life.

Thanks in advance for any advice (and especially any pointers to this sort of beginner info in the literature).


An example of The syntax for a SLC Binary file would be B3:1.2 which would read/write to file 3, word 1, bit 2.
A Logix processor would be something similar such as MainProgram.IA.10 which would read/write to bit 10 of DINT IA which is in the MainProgram Tags. A controller scoped tag would have global in place of MainProgram. I have not used the SLC 500 emulator so I am not sure if that is where the problem is but the above is the syntax that I use to connect to SLC and Logix devices

Hope this helps



This syntax should work on the real drivers but I don’t think the sim driver supports bits.

Thank you, Kevin and Aidan, for your quick responses.

It certainly makes sense that the Simulator might not support every command or datatype. I switched to the Generic Simulator and was able to happily use those BOOLEAN tags over OPC.