CompactLogix tag reset on powerup

lukesnhoj

Member
Join Date
Sep 2012
Location
Perth
Posts
4
Hi

I'm having an issue with a compactlogix that is retaining the controller and program tag data from the last power down and not resetting the values to default/0 on the next power up.
This is causing some issues and I would like everything to reset.

Is there an instruction I need to run or setting I can change that will do this ?
 
You can use a XIC (normally open) S:FS instruction, then use the CLR, MOV, or FLL instructions to reset the tag values as you see fit.

The XIC S:FS instruction will be true only for the first scan after power-up and will do what you require.

You might want to put this in a main routine at the start of your program before executing any of your other program logic.
 
just keep in mind that if you have more than one program in your application you'll have a SEPARATE S:FS bit for each program ...

this might make a difference in operation if you're trying to "reset" tags which are "Scoped" in various programs ...
 
Hi

I'm having an issue with a compactlogix that is retaining the controller and program tag data from the last power down and not resetting the values to default/0 on the next power up.
This is causing some issues and I would like everything to reset.

Is there an instruction I need to run or setting I can change that will do this ?

I don't know what "issues" this is causing you, but generally you most definitely want the controller to restart where it was when the power went down, that is fundamental in most control systems, especially in the process control industries that will have product "in process".

However, if you really want everything reset to default values, you will have to write code to do it. You can either put this as a conditional call to an "initialisation" routine (the condition will be XIC S:FS), you'll need to do this for each "Program" you have. Or you can create a Program and Routine in the controller's "Power Up Handler". This will only be able to address "controller-scoped" tags, so may not be relevant in your application.

Another way to achieve this is to save the project onto an on-board SD card, and configure the controller to always load the program from the card on power-on. Reloading the program from the card will also reload the data stored on it.

You have 3 choices, you must decide which is best for you...
 
Last edited:
Ha, AB makes all variables remnant, you have to manually reset them with the mentioned S:FS tag. It's completely crazy if you're used to selectively making variables remnant or permanent like most other platforms.
 

Similar Topics

I have string array, that after powerup all the data at this array is reset to 0 I need it to save the value it was before the powerup is it...
Replies
3
Views
1,531
My PLC has a Boolean consume tag that gets data from another PLC via ethernet. Is there a way to make the consume tag fail to 0 when the ethernet...
Replies
6
Views
2,741
We manufacture machines with lots of variable parameter set points, mostly DINT's but some BOOL. The issue we have is if a software/project...
Replies
9
Views
2,042
Good Morning , We have a HMI application that has not saved recipes since it was put in a few years ago. Just briefly I looked at the...
Replies
4
Views
2,840
Good Evening , I have 2 CompactLogix PLC's , that I am going to use Produced / Consumed Tags . I would like to tell if both are...
Replies
11
Views
4,038
Back
Top Bottom