the rtc m41t62 works normaly after powon(with a battery cr1220 3V).but sometimes after a few days works wrong.

[ahome.7]

the date and time both go wrong ,like:18-12-24 16:48:01(a right time),turns to 55-04-102 35:18:01(a wrong time)

[Sedric]

Hello

I am seeking a solution too. After poweron m41t62 registers seems to be corrupted. The bcd digits are out of range, also other bits are set.

calculated time hex display

01.03.19 10:42:56     01.03.19 10:42:56.77 CB:01 Weekday:05 RSB:01

->

25.12.33 39:55:30     1f.0c.2d 39:4F:30.17 CB:02 Weekday:06 RSB:01

Reasons for osczillator fail can be

• voltage too low
• interference with quarz (not really - its internal)
• Stop bit

Reasons for wrong data

• Handling stop flag wrong (Mixing reading off-time / current time).
• Not reading registers before writing parts (all time read the register, mask it and combine new data to it)
• Negative undershoot NV Ram corruption AN1009: https://www.st.com/content/ccc/resource/technical/document/application_note/c3/e0/56/c6/d5/12/41/84/CD00004076.pdf/files/CD00004076.pdf/jcr:content/translations/en.CD00004076.pdf

If someone has a better idea... i am looking forward... :D

Greetings,

Richard