Guardlogix Variables

I'm not experience with Allen-Bradley so I am struggling with something I can do very easily with Siemens.

I wonder if anyone could shed some light.

I am trying to read normal Controller or Main Program tags inside the safety program, for example, having a safety reset on the HMI instead of a physical PB

This is proving to be difficult to do, so firstly, is it possible?

The opposite is also proving difficult, for example writing to a normal tag inside the safety program. eg a normal tag of g_xMachineSafe to use for general logic throughout the program.

Thanks in advance.

It is possible using the Safety Tag Mapping. Go to the "Logic" menu at the top and there should be "Map Safety Tags".

Page 12 of this guy: https://www.rockwellautomation.com/...10_IntegratingSafetyUsingLogixControllers.pdf

Out of four possible combinations of read/write and safety/non-safety, you can only do one:

1. You can't write safety tags outside the safety task
2. You can't write non-safety tags in a safety task
3. You can't read a non-safety tag inside the safety task
4. You can read a safety tag in a non-safety task

As to the first two: that's just how it is. It's good practice anyhow to clearly separate safety control from non-safety control, which means you should never be be trying to write to anything safety-related except in the securable safety routine, and likewise with the non-safety controls.

As to the third: as Jeev has mentioned above, you have to map the safety tags. Let's say your reset tag from your HMI is "HMI_Reset". Create a new safety-scoped tag called "Safety_HMI_Reset", and then map the two tags together as Jeev described. The safety tag will match the state of the non-safety tag, and a standard cross reference will pick up that they have been mapped and show references to both tags.

Thanks chaps for the replies. Very helpful.

Its a bit of a clunky system, but got it working today. Thanks again for the replies, great help.

You're welcome, glad we could help!

Just wanted to post another thanks on here. I am working through a similar issue where I need to read some standard tags and control a safety scanner through the safety task. Didn't know about the safety tag mapping until this thread. Thanks so much!