I have a problem with PLC at work. I am working on historical code with a view to upgrading it for a roll out program to all site based PLCs. The code is to be downloaded using memory cassettes, and there is data on the PLC's which needs to be retained. I have re-worked the code and it performs as I would expect as per the following:
1) I download original code (V2.01) to PLC using CX1
2) The PLC simulates a cycle and various values are stored (the key variables are Installation Date and Service Due date).
3) I then download my code to the PLC and the variables have been retained. All so good so far.
The problem is that the factory production line uses PLC code saved using the PLC Backup Tool. When I download the original code to the PLC using this tool, I encounter various issues, but the main one is to do with real time PLC clock values. When I download the code direct from CX one developer, I use the MOVD(083) instruction on A352 through four to give me a variable with the date, month and year. This morning (29/01/2019) the BCD values read as 41, 1 and 25, which translates to 29 (0010 1001), 1 and 19 (0001 1001).
When I download the backed up code using the PLC Backup tool, the values are totally different. I have run the backup files for both codes through a comparison program and there are no differences between them at all.......
Can any one advise if they have experienced this before??