Re: [uCsimm] For exact date

From: 권석근 (kwonsk@mutech.co.kr)
Date: Thu Mar 09 2000 - 21:33:02 EST


Hi, Larry

>It is whatever the crystal is. You can buy both 32.768 and 32.000 kHz
>crystals, and the DragonBall can't tell the difference. Of course,
>whichever crystal you buy has about a 100 ppm error budget (initial set,
>temperature coefficient, aging).
>
>Real Linux kernels can phase slip their internal UTC clock to the
>external timebase at an arbitrary rate, settable to a fraction of a ppm.
>I hope RTLinux can do that too.
>

You mean time correction code (11 minite interval) of linux kernel? or NTP?
Real Linux kernel means Normal Linux kernel?

I've heard that normal destop has seperated RTC chip and they say it uses
cheap crystal. Therefore linux kernel has correction code for this RTC using
system clock (they say it more accurate than RTC crystal).
If what you mentioned was about this, then we do not need this support,
in my thought. Because EZ328 shares same cystal for RTC and system
clock, this correction code could be meaningless.
BTW, david william's idea about reverse(?) correction code from RTC to
system clock was great. In sleep/doze mode (for battery operation),
the only clock running would be CLK32. another idea?
My uCsimm shows correct time after 12 hours, and system date
might be considered as having crystal resolution.

Thanks.
kwonsk.

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