What is the purpose of the external battery of the M221?
1) The help content give us the information the battery of the M221 allow:
-to save the content of the whole %MW area ( %MWi with i>50; note: %MW0-%MW49 are also save without battery)
- to save the RTC clock
2) But in reality the battery is always needed/mandatory because without battery the PLC can’t start in RUN after a PowerOFF, PowerON of the PLC
Within %S75 the PLC program can check when the battery has the be replaced before it become out of order (in average every 4/5 years):
When this bit is Set to 1, it means external battery power is low, so has to be replaced soon
-to save the content of the whole %MW area ( %MWi with i>50; note: %MW0-%MW49 are also save without battery)
- to save the RTC clock
2) But in reality the battery is always needed/mandatory because without battery the PLC can’t start in RUN after a PowerOFF, PowerON of the PLC
Within %S75 the PLC program can check when the battery has the be replaced before it become out of order (in average every 4/5 years):
When this bit is Set to 1, it means external battery power is low, so has to be replaced soon