Posted on February 20, 2004 at 17:39Hello:
We are using an ST real-time clock M41ST85VMH6 in an embedded system design. This model uses the I2C bus interface. We are experiencing some mysterious behaviour of the clock after we let the sytem run for weeks. The clock's time is off quite a bit, and the year register which sould return a value only between 00h ot 99h actually returns the value B7h (in other words, the year reads 2000 + 117 = 2117 instead of 2004). Clearly this year register (at offset 07h in the register map) returns a value out of the bounds indicated in the datasheet:
1) Under what circumstances can this register return a value outside of 00-99h?
2) Are there any know problems with the M41ST85?
P.S. we are using a M4T28-BR12SH snaphat battery. The snaphat battery voltage is ok (3.12V). The clock is running (increments in real-time). Everything works fine except after the unit is powered for weeks...then the time is wrong. If we reset the time, then it works ok (until next time it fails).
I would appreciate any help, insights, opinions...
Regards,
Eric
