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7.8

Have anyone used the M41T93 RTC from ST?

Asked by BeckerTech in Embedded Hardware, Miscellaneous Hardware, Peripherals

Tags: M41T93 RTC Battery backup ST

Hi

I have a technical question regarding the M41T93 Real time clock from ST Microelectronics.  Let me describe the problem.
After setting up the chip, it keeps time, all is well.  It is supposed to keep time when you remove the power unexpectedly, but it does not.  If I probe on the crystal while there is battery backup, then the crystal keeps on oscillating, but it does not keep time.  After the power comes back again, the flags register does not indicate a oscillator fail, thus the crystal did in fact keep on oscillating.  But, even after clearing the Halt bit on start up, the time read is the time of power down.

In short, with battery backup, when power is removed unexpectedly, the oscillator keeps oscillating, but it does not keep time.

Note, I am not confusing this with the timestamp function.  Even after I have cleared the Halt bit, the time which is actually supposed to run in the background of the chip, does not keep running.

What could be the problem?  What am I missing?

Regards
Attachments:
 
The datasheet of the M41T93
 
 
Application note regarding timestamp function
 
[+][-]09/28/09 05:45 PM, ID: 25445039Accepted Solution

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Zones: Embedded Hardware, Miscellaneous Hardware, Peripherals
Tags: M41T93 RTC Battery backup ST
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Solution Grade: A
 
[+][-]08/18/09 04:00 AM, ID: 25121795Author Comment

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