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mjisaacs

Is this possible?

5 posts in this topic

I have a situation where I need to be able to go in and download a program into a SLC5/05 PLC without modifying 1 particular data table. This table is constantly modded by the program, and I want to know if there is anywhere I can copy the data (during the regular scanning) that will not be affected or overwritten when someone plugs in and downloads a modification to the PLC thru the ethernet line?

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You have to store the data externally. An upload/download is all or nothing. Online edits make incremental changes to the code/data. You could also say attach a Micrologix PLC (low cost) and MSG the data back and forth across either Ethernet or via serial link. The Micrologix wouldn't normally be changed...it's just used as a data storage/backup device in this scenario. Usually the only reason to preserve data is if it represents totalizers or recipes. There are much better ways of implementing this than directly in the PLC.

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In a SLC, if you apply static protection to a data table, it can only be modified by a download, or via ladder logic. That would keep folks from accidentally editing it via RSLogix or any communication channel. It would also require that you re-map any data that needs to be updated by a communication channel to non-protected data area and then, in ladder logic, move it into the protected data file. RSLogix5 for the PLC5 did have a handy feature called partial download which would allow you to pick and choose which files and data tables to download, but the SLC family does not offer this.

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This is a slc500 5/05, not a plc5. The partial dl thing would be perfect, but it is rslogix 500 I am using.

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Yes, I understand that, my comment about the PLC5 was simply anecdotal. In the SLC you can apply static protection to the data table. For downloading changes: Open the new file in one instance of RSLogix500. Then open a 2nd instance of RSLogix500 and upload the program from the running machine. (Only you will know whether you need to stop the process or if it is okay to upload while this data table might be changing. That will be application dependent.) Next, you can right click on the data table you want to preserve, and click Copy. Then go to the other instance of RSLogix5000, and right click on the same file number and select paste. Confirm. Voila! The online data is now in the new offline file... This is the best help I can give in your case, and you will just have to make sure all the people who work on this system follow that process in order to preserve the values, unless you want to do something like the other Paul suggests and add hardware/software to backup the data. Hope this helps, Paul

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