SLC 504 issue with TON

Jmeadows7676

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J
Join Date
Oct 2013
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Alabama
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Has anyone ever seen this before. I have a SLC 504 running a very small program and it would seem the TON wouldn't start counting using the orignal 0.01 sec resolution. When changed it to 1sec res it works. I tried a bunch of things before changing resolution like: deleting rung, changing EN state. toggling DN bit. Nothing worked until changing resolution. Also it quits working if i change it back to 0.01.
See images.

Timer 01sec res.jpg Timer 1sec res.jpg
 
Just a WAG... but any chance your online and its not updating fast enough? its really changing but you just cant see it, what is your baud rate? DH+ or serial?
 
geniusintraining said:
Just a WAG... but any chance your online and its not updating fast enough? its really changing but you just cant see it, what is your baud rate? DH+ or serial?
Click to expand...

Its DH+ at 115k but changing the Time base allows the Timer to Complete. 0.01 @ 200 is the same as 1.0 @ 2 right.
 
Last edited:
As a test - just make sure it's safe - with the timer set to 1.0 sec set the preset to 200 (200 seconds) and see if it times past 2 seconds. To see if the ACC goes past 2, or up to 200


Also add a couple branches around the TON and add 2 more TON's just to see what they do. Use unused timer numbers.



One TON T4:100 at 1.0 sec, preset =2
One TON T4:101 at 0.01 sec, preset = 200
EDIT: If they do a third timer TON T4:102 0.01 sec, preset = 32766 to see if it goes past 200

This will let you know if it's something with T4:0 or the way the PLC is running the rung.
 
Last edited:
I_Automation said:
As a test - just make sure it's safe - with the timer set to 1.0 sec set the preset to 200 (200 seconds) and see if it times past 2 seconds.


Also add a couple branches around the TON and add 2 more TON's just to see what they do. Use unused timer numbers.



One TON T4:100 at 1.0 sec, preset =2
One TON T4:101 at 0.01 sec, preset = 200


This will let you know if it's something with T4:0 or the way the PLC is running the rung.
Click to expand...

I was going to try this but would have to do a download because all timers are being used. Is this a possible Hardware issue? I don't know enough about the inter-workings of SLC to know.

Also, when putting preset at 30 seconds timer functioned correctly.
 
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wow.

Does T4:0.ACC ever display anything other than zero, even for a brief moment?

It does appear that T4:0/EN does become 1; could you run that into a CTU e.g. [XIC T4:0/EN CTU C5:99 32767 0], or [XIC T4:0/EN ADD F8:99 1.0 F8:99], or even [NEQ T4:0.ACC 0 ADD F8:99 1.0 F8:99], to see if that bit is perhaps cycling? Although why its reset would have an effect when the Time Base is 0.01, but not 1.0, is beyond me.

Can you print the entire program, along with all the bells and whistles, to a PDF and attach it to a post here?
 
Jmeadows7676 said:
I was going to try this but would have to do a download because all timers are being used. Is this a possible Hardware issue?
Click to expand...

Doubtful. Either what you are seeing is a Windoze artifact or some weird indirect addressing might be stomping on the bits of that timer address.

Hit CTRL +F and put a single opening square bracket for the search field and click Find All.
 
Jmeadows7676 said:
.....because all timers are being used. Is this a possible Hardware issue? ...
Click to expand...


A - Never a good idea. I ALWAYS make sure there are bits, timers, counters, registers (at least 2), and Floats available in EVERY program I write and get the chance to offline edit. I also make sure there are at least 3 unused ladders for future use, as they can be used in online edits. memory in a PLC is free and the only change by blowing up the data files is slightly longer download times, it doesn't change the scan time or operation at all.



B - I have seen some SLC's, and other PLC's, do weird things like, but not exactly, this. It might be something in the firmware won't let T4:0.ACC go over a certain value (say 5 in this case), or T4:0 won't use 0.01 sec timebase. And it might not just be T4:0 - just you haven't found the rest yet.




Another test - replace T4:0 with an unused one and program in T4:0 somewhere else as a test just to see what it does.
 
drbitboy said:
What to the S:35 values look like (they will flash and change quickly, just give your best guess)?
Click to expand...

Going between 1 and 2.

Also, This program has been running without change for 15 years. A vender wrote it and i guess decided not to leave extra Data files. I manage the AssetCentre and have verified there hasn't been any changes to the program.
Crazy how it just stopped working. If i get a chance I will do a download and add some extra Data files.

Also someone asked about putting a rung in. If T4:0.ACC not = 0 then Add 1 to i = i. I did this and it stayed at 0.

🔨🔨🔨
 

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