Reply by ratemonotonic July 15, 20082008-07-15
On Jul 10, 1:43 pm, "Ignacio G.T." <igtorque.rem...@evomer.yahoo.es>
wrote:
> ratemonotonic escribi=F3: > > > Hi All , > > > I am implementing RTC code on an AVR Atmega2560 I have a 32Khz clock > > crystal to TSOSC1 which is used by timer2 in async mode. I have > > configured the clock divide to 8 so the clock to the timer is 32768/8 > > =3D 4096. It is a 8bit so a interrupt should be generated every 16hz > > (4096/256). > > > So on 16 ticks make one second. If I add up second to make 5 minutes > > and light an LED on this event , it is happening within 2minutes. Why > > is this. I have checked the crystal is oscillation at 32Khz. > > =BFExactly 2 minutes, or perhaps 1 minute and 40 seconds?
Investigating further I have varified the it is seeing a clock of exactly 200Khz. Just as an experiment I freeze sprayed the chip and it stopped seeing the 200khz clock. It looks like it is some kind of switching noise it was picking up.
Reply by Ignacio G.T. July 10, 20082008-07-10
ratemonotonic escribi&#2013265923;:
> Hi All , > > I am implementing RTC code on an AVR Atmega2560 I have a 32Khz clock > crystal to TSOSC1 which is used by timer2 in async mode. I have > configured the clock divide to 8 so the clock to the timer is 32768/8 > = 4096. It is a 8bit so a interrupt should be generated every 16hz > (4096/256). > > So on 16 ticks make one second. If I add up second to make 5 minutes > and light an LED on this event , it is happening within 2minutes. Why > is this. I have checked the crystal is oscillation at 32Khz.
&#2013266111;Exactly 2 minutes, or perhaps 1 minute and 40 seconds?
Reply by ratemonotonic July 9, 20082008-07-09
Hi All ,

I am implementing RTC code on an AVR Atmega2560  I have a 32Khz clock
crystal to TSOSC1 which is used by timer2 in async mode. I have
configured the clock divide to 8 so the clock to the timer is 32768/8
= 4096. It is a 8bit so a interrupt should be generated every 16hz
(4096/256).

So on 16 ticks make one second. If I add up second to make 5 minutes
and light an LED on this event , it is happening within 2minutes. Why
is this. I have checked the crystal is oscillation at 32Khz.

Has any on encountered this?


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