Retaining Tags Values in Rockwell(Compact Logix) PLC?

Santosh89 · Apr 2, 2020

Hi All,

I am using a Compact Logix CPU and PanelView 5510 HMI, and i am using Studio 5000 (V32.02) platform for developing the program for both PLC (Logix Designer) & HMI (View Designer).
I am familiar with Siemens products, this is my first project experience with Rockwell as well, my question is how to retain the tag value which is provided from the HMI to PLC, because after power cylce/during downloading the program backup to PLC the values entered from HMI to PLC tags are getting reset. I need to retain those tags values after power cycle also.

Note: I am using Program Based tags for Parameters entry in HMI.

Can anybody help me with this please and also if you can provide me any document or links related to the preliminary settings (mandatory) or programming methodology i need to follow in both PLC & HMI products mentioned above.

Regards,
Santosh

rupej · Apr 2, 2020

So after a power cycle, any data inside the PLC is inherently retained unless some logic or some external device overwrites it. If you're having problems with data changing after a power cycle, I think you need to look at those possible causes.

For downloads, Rockwell has an application called "Data Preserve Download Tool" which allows you to download the logic without changing the data. I think that's what you're looking for.

diat150 · Apr 2, 2020

do you have the logic set to load from a memory card or something?

Santosh89 · Apr 2, 2020

Tags Retaining during Program Download Rockwell(Compact Logix) PLC

Hi Rupej & diat150,

Sorrry for the misleading question, just checked & reconfirmed now that the tags are not reseting during the power cycle, its happening during the program downloading to PLC (Currently i have kept the CPU keyswitch in 'REMOTE POSITION' i.e. Remote Run Mode.
Whenever i am downloading the program to PLC the CPU is going to Remote Program mode once after the CPU comes back to Remote Run Mode then if check the Tags values those are reseted.

I have directly linked the 'Program Scope Tags' to HMI, then from that tags i am moving those values local internal tags for the logic.

Regards,
Santosh

AustralIan · Apr 2, 2020

Yeah, you need to find a workflow that works for you, because the download always downloads the tag values.

1. Data preserved download tool.
This is/was an optional install. Sometimes works, sometimes doesn't. I don't trust it, because if it doesn't work, you lose the settings forever.
2. Use online change to copy and paste the changes.
a) project compare.
b) Copy some logic across.
c) project compare again.
d) copy some more logic across.
e) project compare until all equal.
Works well for small changes, but even then has some human error.
3. Stop the machine so all the tags aren't changing. Upload from plc. Merge changes into the uploaded project. Download. Start machine.
4. Stop the machine so all the tags aren't changing. Upload from plc. Merge all tag values into the modified project. Download. Start machine.
5. Use recipes to save all the values that should be RETAIN PERSITENT. Download. Download recipe. This is similar to what option 1 does but for specific tags.
6. Get it right first time and never change the code for the next 25 years.

My go to is option 2.
Does anyone have a better way? Anyone had more luck with the DPDTool?

Holmux · Apr 2, 2020

AustralIan said:
Yeah, you need to find a workflow that works for you, because the download always downloads the tag values.

1. Data preserved download tool.
This is/was an optional install. Sometimes works, sometimes doesn't. I don't trust it, because if it doesn't work, you lose the settings forever.
2. Use online change to copy and paste the changes.
a) project compare.
b) Copy some logic across.
c) project compare again.
d) copy some more logic across.
e) project compare until all equal.
Works well for small changes, but even then has some human error.
3. Stop the machine so all the tags aren't changing. Upload from plc. Merge changes into the uploaded project. Download. Start machine.
4. Stop the machine so all the tags aren't changing. Upload from plc. Merge all tag values into the modified project. Download. Start machine.
5. Use recipes to save all the values that should be RETAIN PERSITENT. Download. Download recipe. This is similar to what option 1 does but for specific tags.
6. Get it right first time and never change the code for the next 25 years.

My go to is option 2.
Does anyone have a better way? Anyone had more luck with the DPDTool?

This is right on the money

There is a slight difference in how you work i a Siemens PLC compared to AB, unless you are making dramatic changes in the program there are normally no reason to download the program to the PLC, once your started the plc the first time.

I do 99% of my AB work online, this way you will never have a problem, I have never been in a position where I needed DPDTool, if I have to expand something in the PLC that requires a download, I will use option 3 in AustralIan's list

daba · Apr 2, 2020

Most times your PLC program edits can be done online, and do not require a download. Under this circumstance your tag values are not affected.

Sometimes your program edits may have to be done offline, and this will mean that a download will be required after your edits.

This is how I manage preserving data values....

1. Go online to the controller. This will ensure you have identical logic code.

2. Put your processes into a "safe state", so that tag values will not change.

3. Save the project, you will be prompted to save the current tag values, say Yes to that. Tag values will be uploaded from the controller and saved.

4. Go offline.

5. Make the program changes you couldn't do Online.

6. Download the project. The download will include the tag values saved in step 3.

7. Restore your controller to Run mode.

Follow this method to ensure you have new running code, with the latest tag values.

I've never used the DPDTool, or had the need to.

Santosh89 · Apr 3, 2020

Hi All,

Thanks for the valuable suggestions and feedbacks.

Coming from Siemens background i found it bit strange to understand few programming things with Rockwell, but anyways we need to deal with it.!

As i sometimes need to give remote support by accesing the PC which is connected to the controller, it will be difficult to follow the Online edit everytime, so i need to rely on Offline modification/updates of the program. On this time it will be very difficult to spend more time just for downloading the backup itself..!
So in this case i am think of using/testing the 'daba' suggestion to overcome my issue and hoping it will work well for me..? But what is the 'Safe state' in the processor..?

And another query where t oprovide the default value for those tags which is assigned with HMI from PLC, i am using AOI and i am defining the default values over ther in those tags, but i couldn't able to figure out where to provide the same default values for tags assigned with HMI..? can you guys help me this please..?

Regards,
Santosh

Holmux · Apr 3, 2020

I don't fully understand why you dont do your edits online, if speed is an issue, this is by far the fastest way to make changes in the PLC.

But if you choose to make a download and you have some default values that would work, you can make a routine that fires whit the first scan, moving the default values into your tags.

Retaining Tags Values in Rockwell(Compact Logix) PLC?

Santosh89

Member

rupej

Member

diat150

Lifetime Supporting Member

Santosh89

Member

AustralIan

Member

Holmux

Lifetime Supporting Member

daba

Lifetime Supporting Member

Santosh89

Member

Holmux

Lifetime Supporting Member

Similar Topics