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RE: [avr-chat] Newbie fuse selection..attempt 2

From: Ben Mann
Subject: RE: [avr-chat] Newbie fuse selection..attempt 2
Date: Fri, 22 Jul 2005 09:05:14 +0800

Some further thoughts –


* How do you know it’s dead?


* Have you another mcu to test with?


* What capacitors are you using? 22pf should be fine.


* Is it a parallel cut crystal? A “series cut” crystal would not work, but these are rarer.


* Are you trying this on a breadboard? It should still work but leads need to be kept as short as possible. Try running without any peripherals connected (ie, just connect VCC, GND, the XTAL pins and your programmer – you’ll know the crystal works if you’re able to read the fuses from AVR Studio or program the device – if this solves it then start looking at the rest of your circuit for problems).


* If changing the setting worked properly, you can still use a lower value crystal such as an 8MHz, which you can use to test the chip (and your 16mhz crystal, which may be defective).




Its an AtmegaGA8535 16PU 0512A. How does this fair with your speed theory - and how do you know?



----- Original Message -----

Just a thought, does your part have ATMEGA8535-16PC (or -16AI) marked on it? If you are using an -8xx mcu then I could imagine it becoming unhappy with the high speed crystal.



Hi everyone,

OK, I've put this off far to long now, but I have to up my frequency. I have ticked the (CKOPT) and (CKSEL=1111 SUT=11) and my Atmega8535 has died just as it did last time. It has a new crystal and caps but something is wrong. Any help most apreciated, what can it be?


Thanks Peeps

----- Original Message -----
> Tick CKOPT, you need this for oscillators > 8MHz or no oscillations will be
> seen.
> Tick one of the "Ext Crystal/Resonator High Freq" options such as the last
> one (CKSEL=1111 SUT=11).
> Ben
> ________________________________________
> I am trying to run an Atmel8535 off of a 16MHz crystal (and recomended caps)
> but have found out it is only running from an internal source - my scope
> shows no oscillations from the Xtal.
> After previously disabling a chip, I have sought advice and have been told
> the fuse settings to use. Although I'm not sure yet how this relates to the
> data sheets advice, despite people trying to tell me, it is the programmed
> and unprogrammed remarks that are throwing me off. Could someone please
> confirm than in AVR Studio4 I should tick the three relevant boxes, despite
> the (prog) remarks here...
> CKSEL3..0 = 1111 (unprogrammed)
> CKOPT = 0 (programmed)
> SUT1.0 = 11 (unprogrammed)
> Thanks People

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