AVR-Chat

Don't some of them have to be cleared by erasing the chip and eeprom?
Are there some that can only be cleared using high-voltage parallel 
programming?

Regards,
   JJ

On Friday, Apr 16, 2004, at 13:24 US/Eastern, Mike Bronosky wrote:

> Can be set and cleared at will!
>
> ----- Original Message -----
> From: erikc <firewevr@airmail.net>
> To: <AVR-Chat@yahoogroups.com>
> Sent: Friday, April 16, 2004 11:53 AM
> Subject: Re: [AVR-Chat] Re: keypad and mega64
>
>
>> A rank newbie has a question.  These "fuses" that you
>> mention, are they one-time programmable (like a real fuse)
>> or are they really something like an EEPROM cell that can be
>> set and cleared at will?
>>
>> Erikc  - firewevr@airmail.net
>> ///
>> "An Fhirinne in aghaidh an tSaoil."
>> "The Truth against the World."
>>         -- Bardic Motto
>>
>>
>> ----- Original Message -----
>> From: "chris atwan" <chrisatwan2000@yahoo.com>
>> To: <AVR-Chat@yahoogroups.com>
>> Sent: Friday, April 16, 2004 14:48
>> Subject: Re: [AVR-Chat] Re: keypad and mega64
>>
>>
>>> Brian,
>>>
>>> I verified that the JTAGEN fuse is "1".  Any ideas??
>>>
>>> Chris Atwan
>>>
>>>
>>> Brian Dean <bsd@bdmicro.com> wrote:
>>> Hi Chris,
>>>
>>> On Fri, Apr 16, 2004 at 01:56:39AM -0000, chrisatwan2000
>> wrote:
>>>
>>>> I checked my fuses with AVR Studio and the following
>> fuses are set:
>>>>
>>>> BOOTSZ=11
>>>> BODLEVEL=1
>>>> CKSEL=1111 SUT=11
>>>>
>>>> Any ideas??
>>>
>>> The above fuses are in the low fuse byte.  You want to
>> look at the
>>> "high" fuse byte - the JTAGEN bit is bit number 6.
>>>
>>> In Atmel terminalogy, a fuse is "set" or "programmed" if
>> it is '0'.
>>> It is "unset" or "unprogrammed" if it is a "1".  However,
>> I think in
>>> AVR Studio, a check mark on the fuse setting sets it to a
>> "0", i.e.,
>>> programs the fuse.
>>>
>>> Look at the high fuse byte, specifically bit number 6.  If
>> it is a
>>> zero, then the JTAG debugging interface is enabled.  If it
>> is a one,
>>> then it is disabled.  It is enabled by default, so unless
>> you disabled
>>> it, it is most likely still enabled.  If it is enabled,
>> then that
>>> would most likely explain the problems with your program
>> not getting
>>> the expected results when using PORTF.
>>>
>>> For more info, the "Memory Programming" section of the
>> ATmega128
>>> datasheet.  The high fuse byte is described on page 292 in
>> the version
>>> I have.
>>>
>>> -Brian
>>> --
>>> Brian Dean
>>> http://www.bdmicro.com/
>>>
>>>
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