1. Interfered by program.
2. Communication partner modified data touch screen, plc.
3. EMC interference, CPU can not work properly.
4. MMC card or CPU failure.
5. But also to determine whether the work is not an abnormal operation to do Memory Reset operation (with power to plug and unplug the card).
6. Confirm the properties of the DB block: Un-Linked Non-Retain.
The main reasons for data loss include these three situations:
1. The actual value of the DB block is suddenly changed to the initial value during operation.
2. Inconsistency between FB, FC and backup program consistency check in PLC.
3. Loss of code, configuration and other information in the program.
The first case may be due to the fact that the current value in the load store was overwritten by the value in the main store due to the previous execution of Copy Ram to Rom, after which the value in the load store was returned to the main store due to the execution of a storage reset and other similar operations;
The second possible cause should be the presence of inconsistent data in the card caused by pulling out the MMC card during the run;