Programming Fuse Bits in ATmega8

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knut_
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Posted by knut_: Fri. Dec 30, 2005 - 01:14 AM
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Hi
I have a broblem with programming fusebits... when I program fusebits on chip I cant't anymore re-program chip.

command line is;
avrdude -pm8 -Plpt2 -cstk200 -u -U lfuse:w:0xEF:m

only low fuse byte chanced (0xEF)
so there is no chance to program SPIEN (Enable Serial Program and Data Downloading), because it is in high fuse byte bit, 5.

Everything works fine, but re-programming flash is not possible.

msg is:

avrdude: AVR device not responding
avrdude: initialization failed, rc=-1
Double check connections and try again, or use -F to override
this check.

How I can re-program flash??

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Tools, Compilers and General Programming
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dl8dtl
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Posted by dl8dtl: Fri. Dec 30, 2005 - 07:09 AM
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You could not change the SPIEN bit from within ISP anyway.

You're running on an external crystal. What's the frequency? Did
you measure it really runs at the designed frequency?

Jörg Wunsch

Please don't send me PMs, use email if you want to approach me personally.

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knut_
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Posted by knut_: Fri. Dec 30, 2005 - 10:59 AM
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Crystal is 2.457600Mhz, but it works much slower!

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dl8dtl
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Posted by dl8dtl: Fri. Dec 30, 2005 - 11:13 AM
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That's what I was afraid of.

If your clock is too slow, the rather fast SPI clock from
avrdude doesn't work anymore. Try feeding an external
clock into the ATmega.

Of course, you have to analyze why the crystal doesn't
work as expected.

Jörg Wunsch

Please don't send me PMs, use email if you want to approach me personally.

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knut_
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Posted by knut_: Fri. Dec 30, 2005 - 12:31 PM
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Thanks Jörg problem solved !

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