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

From: gecko gecko
Subject: RE: [avr-chat] Newbie fuse selection..attempt 2
Date: Fri, 22 Jul 2005 03:15:01 -0500

Some further answers –


* How do you know it’s dead? - The fuses will not read in AVRstudio, the program on it doesn't run(serial output (what i am trying to fix by using a stable crystal))


* Have you another mcu to test with? - A new MCU works just fine (i've no more to ruin though!)


* What capacitors are you using? 22pf should be fine. - 22pf is what I am using


* Is it a parallel cut crystal? A “series cut” crystal would not work, but these are rarer. - I have no idea, it was just a cheap 16MHz crystal from farnell, i'll look out next time though, and change as soon as I can


* 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). - It is on a breadboard, with short leads too! but I'll play as you sugest and post if it works!


* 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). - The 16MHz crystal is new, as this is the first thing I changed on the last attempt where i believe i changed to the CKSEL=1111 SUT=11 fuse only, leaving the rest un altered.


Thanks for such a comprehensive reply!


Any further help  welcome







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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