ryangriggs
Lifetime Supporting Member
Hello, I am tasked to update a CompactLogix PLC program on a live system. The updates I need to make involve changing a user-defined data structure (UDT) within the program.
This apparently can't be done online, and requires me to edit the program offline, then re-download it to the controller.
The controller has a lot of counters, configuration settings, etc which should not be modified.
How can I ensure the tag values won't be changed when downloading the new program? I can't see any way to download only the program without downloading the tag values also.
The only way I can see to do this is to:
1. Upload the current program while online. (copies all tag values as they currently are)
2. Go offline
3. Modify the UDT
4. Download the program to the controller
At this point all tag values will be copied from what they were in step 1.
Is there a better way to achieve this without needing to download tag values and set them back to whatever they were in step #1? For example, if a counter continues to run after I upload in step #1, then when I download in step 4, the counter will be reset back to the previous value, thus losing any change since step #1.
Thanks for any pointers.
EDIT: I think this thread basically answers the question: http://www.plctalk.net/qanda/showthread.php?t=26302
This apparently can't be done online, and requires me to edit the program offline, then re-download it to the controller.
The controller has a lot of counters, configuration settings, etc which should not be modified.
How can I ensure the tag values won't be changed when downloading the new program? I can't see any way to download only the program without downloading the tag values also.
The only way I can see to do this is to:
1. Upload the current program while online. (copies all tag values as they currently are)
2. Go offline
3. Modify the UDT
4. Download the program to the controller
At this point all tag values will be copied from what they were in step 1.
Is there a better way to achieve this without needing to download tag values and set them back to whatever they were in step #1? For example, if a counter continues to run after I upload in step #1, then when I download in step 4, the counter will be reset back to the previous value, thus losing any change since step #1.
Thanks for any pointers.
EDIT: I think this thread basically answers the question: http://www.plctalk.net/qanda/showthread.php?t=26302
Last edited: