Help with Micro820 RTO ET and power cycling

JZerb

Member
Join Date
Oct 2016
Location
Here
Posts
421
so i have a micro 820 for a small project im working on and im having a **** of a time figuring out how im going to get a retentive timer to pick up where it left off on the power cycle since the controller looses all of its ET data.

-user enters timer MIN and SEC on panelview 800, easy using a UDFB that executes DINT to TIME
-display on HMI shows timer elapsed time, easy using a UDFB that executes TIME to DINT

issue becomes how to get this all to work on a power cycle properly, since as ive stated the RTO looses its TIMER ET value. so i have to not only diplay the prpoer elapsed time on the HMI still, but have the RTO continue its ET where it left off, which seems to not be working because im unable to just MOV a value into the timers ET on the first PLC scan like i thought i could and be on my way. been having a go at it for a few hours and im totally stumped, any suggestions would be greatly appreciated.
 
In the parameters of the RTO make sure you have checked the "Retained" checkbox, this will keep current values even if there is a power cycle.
 
In the parameters of the RTO make sure you have checked the "Retained" checkbox, this will keep current values even if there is a power cycle.

that i have, the issue becomes that the ET on the RTO is not retained, and cannot be retained according to AB Tech Support after i read in the manual it wasnt doable i wanted to confirm.

so where i get jammed up is that if i have a timer for say 1min 30sec, i use a UDFB to take those two DINT and put them into a TIME Global Variable. Then that TIME Global Variable is the PT of the RTO. say 40 seconds expires off the timer, I use that ET, which is a TIME Global Variable, and then use a UDFB for TIME to DINT and display on the HMI those two DINTs to view cycle time elapsed. once i power cycle the machine that ET from the RTO goes to 0. so now i have no way to make the calculation to properly show on the HMI what time has elapsed. it just goes to 0 since now the ET on the RTO doesnt retain and therefore resorts back to zero.

edit:first time using a Micro 800 series processor, loved that i could control a drive with the 0-10v outpt oboard stock for that the Micro820 costs, but cannot believe that im having such an issue with this timer logic.
 
that seems right, if you set the values you wanted to retained they do retain through a power cycle, its just the ET does not, regardless if i set that value to be retained or not

micro800retention.jpg
 
Last edited:
Thanks for the information, I will make a note of that. I use the RTO for several different timing function but all of our units are on "Battery Backup" so this is probably why I have not had any problems.

Something I will look out for.
 
unfortunately i have to account for all scenarios, like for this unit if someone decides to just turn the thing off while its running, it needs to recover. the micrologixs this is no issue, with these Micro800s apparently it is, and thats regardless of what Micro800 you use i was told its from the 800 to the 870 they all behave in the same way.
 
so for anyone who may stumble upon this. you have to go into the Local Variables and find the RTO instruction, click on the + sign to see the drop down of all the tags within that RTO and then ALSO check the box in the retain column for the .ET on said timer. THEN, everything works as it should
 

Similar Topics

Hello all! I come asking if anyone has had this situation. I have a Micro820 controller that sits idle for some long periods (I use it to count...
Replies
5
Views
1,276
Hey everyone, I'm pretty new here, but have been working lightly with AB PLCs for a while now. I've recently hit a stumbling block that I'm hoping...
Replies
4
Views
1,326
I have a Micro820 here that will eventually be used as a slave device and will have information pulled from it serially. I need to test the...
Replies
14
Views
4,412
Hello I am programming AB micro820 with CCW. I need to connect a bander to an output and the bander can only work once even if the output stays...
Replies
0
Views
1,878
Hello. I am beginner plc programmer working in a project at work using micro820 and CCW. Every time a modify the program I have to download the...
Replies
6
Views
3,481
Back
Top Bottom