Moving from Rockwell to Siemens Tips

Hello Guys,

I have worked all my experience with AB PLC and now starting to work with Siemens S7-1500. Can someone tell me If I add a tag to an existing DB I need to make a snapshot and copy snapshot to start values? Otherwise the values will be lost? Why do we do this? In AB there is no such concept? Please share your tips

The DB is a container of values. If you change the container and download, the values in that offline container will overwrite the container (and its values) in the PLC. A snapshot captures the values from the PLC and put them in the container in the project, so that when you add values to the container and download, you can restore the values again to the PLC.

When you download a DB from your project in Siemens, a similar thing happens with AB when you do a download of the program. All your offline values replace the values in the PLC.

sigmadelta said:

The DB is a container of values. If you change the container and download, the values in that offline container will overwrite the container (and its values) in the PLC. A snapshot captures the values from the PLC and put them in the container in the project, so that when you add values to the container and download, you can restore the values again to the PLC.

When you download a DB from your project in Siemens, a similar thing happens with AB when you do a download of the program. All your offline values replace the values in the PLC.

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In AB once I upload the plc project and can makes the changes and download and the values are retain.

In siemens I need to check what my initial values are. If my initial value is 0 and the actual value is 999 . What happens when you download. Will your actual value now be 999 or 0??

In AB once I upload the plc project and can makes the changes and download and the values are retain.

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Yes, if you STOP the CPU when you download. With Siemens S7, you can do this in RUN.

In Siemens I need to check what my initial values are. If my initial value is 0 and the actual value is 999 . What happens when you download. Will your actual value now be 999 or 0??

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0 (because of "re-initialize" after you modify a data block)

...until you transfer your snapshot to the PLC.

My screenshot is from V16. There is an option called "Keep actual values", when I activated this, made changes to the DB and downloaded, the value in the PLC was kept. Without this option, I had to download the DB (which re-initializes it), then transfer my snapshot to the PLC to have the values I had captured before. You can also copy snapshot to the start values, which means if you download and it re-initializes, it will go to values you had "snapshotted" into the start values.

bornwild said:

In AB once I upload the plc project and can makes the changes and download and the values are retain.

In siemens I need to check what my initial values are. If my initial value is 0 and the actual value is 999 . What happens when you download. Will your actual value now be 999 or 0??

Click to expand...

Notice how you are applying double standards between platforms... if I write your first sentence and simply replace the brand, it's also true.

In Siemens once I upload the plc project and can makes the changes and download and the values are retain.

Click to expand...

cardosocea said:

Notice how you are applying double standards between platforms... if I write your first sentence and simply replace the brand, it's also true.

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Sorry but in Siemens you need to upload each DB block and make a snapshot. Correct me if I am wrong.

sigmadelta said:

Yes, if you STOP the CPU when you download. With Siemens S7, you can do this in RUN.



0 (because of "re-initialize" after you modify a data block)

...until you transfer your snapshot to the PLC.

My screenshot is from V16. There is an option called "Keep actual values", when I activated this, made changes to the DB and downloaded, the value in the PLC was kept. Without this option, I had to download the DB (which re-initializes it), then transfer my snapshot to the PLC to have the values I had captured before. You can also copy snapshot to the start values, which means if you download and it re-initializes, it will go to values you had "snapshotted" into the start values.

Click to expand...

So is keep actual values only available in TIA V 16

Sorry but in Siemens you need to upload each DB block and make a snapshot. Correct me if I am wrong.

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You should be able to right-click either the Program Blocks folder or PLC object, and do "Snapshot of the actual values" and this will do it for all DBs.

So is keep actual values only available in TIA V 16

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No, it's available from at least V13. The icon looks like this:

sigmadelta said:

You should be able to right-click either the Program Blocks folder or PLC object, and do "Snapshot of the actual values" and this will do it for all DBs.

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Ah ok got it. Thanks. This is required only I make a change to a DB right? what about When you add new hardware do we still need to do this. Sorry, I am trying to get the hang of siemens

This is required only I make a change to a DB right?

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Yes.

When you add new hardware do we still need to do this.

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No.

bornwild said:

Ah ok got it. Thanks. This is required only I make a change to a DB right? what about When you add new hardware do we still need to do this. Sorry, I am trying to get the hang of siemens

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Every time the PLC goes from STOP to RUN, all data not marked as "Retentive" gets set back to its start value. I/M/Q memory all goes to 0. All tags in a DB go to whatever value is assigned as the start value. You can set the start values to be equal to the snapshot values, which is the easiest way to ensure that your start values are useful.



HW downloads do stop the PLC, so if you want the data to stay 100% the same, you either mark it as retentive, or make sure your start values are what you want the data to return to.

Originally posted by sigmadelta:

No, it's available from at least V13. The icon looks like this:

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WOOHOO!!! It's been a while since a customer has asked us for a Siemens control system on a machine so my Siemens experience is fairly dated. This is a big deal. The right-click snapshot is even better. This definitely makes it easier to keep your offline data up to date.

bornwild, as long as you approach things with an open mind I don't think you will have much trouble with the application software structure or concept. It isn't as bad or as different as some make it out to be and there are things you will find that you like. I think you are right now running into the kinds of things that will drive you nutty. How do you do what was a seemingly simple thing in a Rockwell product using the Siemens platform. It really comes down to familiarity. If you have a local Siemens rep that can give you some upper level training on Portal I would recommend it. Just knowing where functions are located (like the data snapshot) will make your experience much more enjoyable.

Keith

Every time the PLC goes from STOP to RUN, all data not marked as "Retentive" gets set back to its start value.

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Thanks for that addition. After over 2 decades of DBs being retentive by default in STEP 7 V5.x (you had to go and make them non-retentive if you wanted!), now you have to do the opposite.

I just kind of skimmed over that. I need to remember that one. As sigmadelta said, I'm more used to the old Step 7 stuff. I wouldn't normally think about this.

Keith