|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 its 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 youll know the crystal works if youre 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.
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?
----- Original Message -----
> Tick CKOPT, you need this for oscillators > 8MHz or no oscillations will be
> Tick one of the "Ext Crystal/Resonator High Freq" options such as the last
> one (CKSEL=1111 SUT=11).
> 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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