When starting up for the first time, or replacing a module, or when a battery
fails, or the PLC requests a MRES, or the PLC operating system is upgraded,
the complete memory reset is absolutely necessary:
1. Set PLC start-up switch S4 to position “3”.
2. Turn NCK start-up switch S3 to position 1 (which will clear the DRAM
between the NCK and PLC).
3. Perform POWER ON and hardware RESET.
4. PLC general reset:
上述应该是一些特殊情况，请参考。