RTC cleared after reset

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wBoellmann
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Posted by wBoellmann: Sat. Aug 11, 2007 - 04:09 PM
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Hello everyone,

i found the Real Time Clock to be reset to zero after pressing the reset button of the NGW100. Doing a "reboot" in Linux the content is not touched.

Did anybody know if this is a software bug in "Das U-Boot" or a hardware "feature"?

Werner

... the only thing you cannot unscramble is eggs...

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Tools, Evaluation and Development Kits (AVR-related)
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KaiBen
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Posted by KaiBen: Sat. Aug 11, 2007 - 04:55 PM
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Hi Werner,

I think this is a hardware feature. Indeed, pressing the reset button of the NGW100 asserts the RESET_N pin, what generates a hard reset, while the `reboot' in Linux uses the Watchdog Timer to generate a soft reset. Only a hard reset will reset the RTC.

Take a look at the PM RCAUSE register. You should read in the complete MCU datasheet the chapter Power Manager \ Functional Description \ Reset Controller for further details.

++
Ben

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how
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Posted by how: Sat. Aug 11, 2007 - 07:26 PM
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Actually, Linux uses the OCD system to trigger a reset, not the watchdog, but the rest of your comment makes sense.

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squidgit
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Posted by squidgit: Sun. Aug 12, 2007 - 06:18 AM
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wBoellmann wrote:
Did anybody know if this is a software bug in "Das U-Boot" or a hardware "feature"?
It's more a hardware restriction ;). The RTC is volatile, it gets reset on hard reset. You can put a non-volatile external rtc on the board if you need.

-S.

Blag: http://www.niasdigital.com/blag

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