(AB,Siemens) Going online with a different project on PC

I went online with a Micrologix 1500.
The thing is that when i was trying to go online I used the "Browse" fuction and then i selected the folder where the project was in, but the window said that no project matched so I selected one file and used the "Use user file" function.
I went online but now the online project had more lines than the offline project.So what I understood is that the project was updated with the
differences.
am I wrong?
can you do the same in STEP7 using the Compare Blocks online/offline fuction.

Yepp in Siemens you can use Compare Blocks. That will also point out where the difference is/are in the code. If you are online of course.

Good Luck

Greetings plc-friend,



and welcome to the forum ...



first things first ... it doesn’t matter which file stored on your computer you open first ... when you go ONLINE with an Allen-Bradley processor, the ladder program that you see on your screen will always be the program that is currently inside the PLC processor ... specifically, all of the rungs and program instructions that you see on your “ONLINE” screen, will be exactly the same as the rungs and program instructions that are presently stored inside the PLC processor ... going further, if the “OFFLINE” file that you opened BEFORE you went ONLINE with the processor had a different set of rungs and instructions, then the offline program file on your screen will be replaced by the PLC processor’s program as soon as you go online ...



now as for the comments and other documentation ... (things like: Limit Switch 14, Pump A, etc.) ... Allen-Bradley refers to this documentation as the “database” ... note that this is different from the “data tables” ... these database comments are typed in to help us humans understand what is going on inside the processor ... but a PLC-5 or SLC-500 type processor NEVER sees these comments ... specifically, the comment database is never downloaded to the PLC processor ... the database is contained only in the OFFLINE program file on your computer ...



now then ... IF you have your RSLogix system properly configured, when you simply go online with a processor, the RSLogix software will query the processor for its name and its program checksum ... if those two items match the name and the program checksum of a file stored on your computer, then the software should go online without any problem ... you’ll see the ladders inside the processor ... and the database comments from the offline file ...



but let’s just say that someone has made a change to the program inside the processor ... so the online and offline processor names match ... but the program checksum does not match the checksum stored in any of the offline files stored on your computer ... in that case, RSLogix will usually provide you with a list of offline files that MIGHT be suitable for documentation for your PLC’s online program ... you choose the one you think is best, and then click the “upload and use file” button ... basically this means “UPLOAD the program ladders from the PLC processor - and USE THIS FILE (which is highlighted) for the documentation” ...



but then ... sometimes people defy prevailing wisdom and store their offline files in different folders all over their computer hard drives ... why? ... maybe for the same reason they wear their shoes too tight ... who knows why? ... but in those cases where the RSLogix software does not know exactly where to look for the offline program files, then you’ll have to browse around manually until the proper offline file has been found ...


as for Siemens ... sorry but I don't go there ...

I hope this helps ...

RSLogix Compare

RSLogix 500 has a good compare utility. You can use it to compare two files on your PC or to compare a file on your PC to the program running in the PLC (assuming you can go online). From the Tools menu select Compare. I personally prefer uploading the PLC program and then 'Saving As' to a new file name and then using the compare utility offline. But you can do it however you want.

One more thing, I think there was a version of RSLogix that did not have the compare utility.

Another question

Thank you for your help Guys.
my new question is:
In STEP7,when you compare blocks and see the differences between the offline and online projects. Could I use the diffenret offline project to monitor?
are the new rungs added to the offline project?


Thank you alot

In STEP7, if you use the "Block Comparison" and click the "Details" button, you should see the offline block next to the online block in the Program Editor. At this point you can make changes to the offline block and save those changes.

As for monitoring, if you open an offline block from your PC in the Program Editor and then try to monitor the PLC but the offline block does not match the online block in the PLC you will get an error message. The message about being unable to monitor the block because the online block does not match the offline block. You are given the choice of downloading the displayed block to the PLC and then monitoring. If you choose not to do this, you just see the original block from your PC (offline) but you are not monitoring the PLC.

On the other hand, if you choose to download and monitor, then the offline version is downloaded to the PLC and you are put in monitor mode. This may be a bad thing if the version on the PLC (online) is the current or good version because it will be overwritten by what is on you PC.

Perhaps what you should do is either open the Online view (View -> Online) and copy the newer blocks from the Online to your Offline project. Or just upload the project from the PLC to your PC (PLC -> Upload to PG). Your offline project on your PC should match the online project on the PLC.

I am not sure if this answers you question.

Thank you so much, now everything is clear