Timer ticks occurring much more faster

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- ratemonotonic
  
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posted
15 years ago

Wed, Jul 9, 2008 4:04 PM

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?

BR Rate

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- Ignacio G.T.
  
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posted
15 years ago

Thu, Jul 10, 2008 12:43 PM

ratemonotonic escribió:

¿Exactly 2 minutes, or perhaps 1 minute and 40 seconds?

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- ratemonotonic
  
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posted
15 years ago

Tue, Jul 15, 2008 9:01 AM

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.