AVR-Chat

Oh!  Of course.  That kinda went without saying I thought.  So, you
basically need the clock whether it's internal, external crystal, or
external clock and it must be running.  Gotcha :)



-----Original Message-----
From: John Johnson [mailto:johnatl@mac.com] 
Sent: Sunday, March 28, 2004 12:20 PM
Subject: Re: [AVR-Chat] Re: start AVR

The chip must have a clock source to be programmed. Either internal or
external. When you receive the chip, it is configured to use the 
internal oscillator.
If you program it to use an external oscillator, you must have the 
external
oscillator running to reprogram the chip.

Regards,
   JJ

On Sunday, Mar 28, 2004, at 15:12 US/Eastern, LightYearCS wrote:

> Wait.... What?
>
> "There are fuse settings, however, to run with an external clock 
> signal,
> in which case, unless you have an external clock attached you will
lose
> the ability to reprogram the chip after you make that change."
>
> Are you saying that if I use an external clock I can't upload the
flash
> anymore?  I hope not.
>
> I'll be using an external crystal and perhaps an external clock chip.
> I'll need some accuracy because this device is used for timing
> applications up to about 80 seconds.
>
> Barry
>
>
> -----Original Message-----
> From: Brian Dean [mailto:bsd@bdmicro.com]
> Sent: Sunday, March 28, 2004 6:57 AM
> Subject: Re: [AVR-Chat] Re: start AVR
>
> On Sun, Mar 28, 2004 at 12:38:03AM -0800, LightYearCS wrote:
>
>> So, really SPI is it right? :)
>
> Yep.  Like Larry said, though, be careful setting fuse bits.  By
> default, the chips come set to run with the internal oscillator at 1
> MHz.  You'll normally reprogram the fuses to run at a higher
> frequency, and/or to use an external crystal.  There are fuse
> settings, however, to run with an external clock signal, in which
> case, unless you have an external clock attached you will lose the
> ability to reprogram the chip after you make that change.  You can
> recover by feeding in the external clock that the chip is expecting in
> that configuration, reenter programming mode, then reset the fuse bits
> as needed.
>
> Just a little something to be aware of - this is probably one of the
> more common problems when you had programming communication
> established at one point, but for "some reason" it doesn't work now.
>
> Also, for ISP programming purposes, which uses an SPI protocol, the
> ATmega64 DOES NOT use the MISO/MOSI pins as labeled on the chip
> pinout.  Look for PDO and PDI instead.  It does use the SPI SCK pin
> for clock, though.  Be sure you double check your programming header
> is connected to PDO and PDI instead of MISO and MOSI before ordering
> your boards :-) See the "memory programming" section of the datasheet
> to double check the pin mapping for ISP programming.
>
> -Brian
> -- 
> Brian Dean
> http://www.bdmicro.com/
>
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