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[avr-gcc-list] Re: Troubles uploading to a Mega103

From: Ludovic COURTES
Subject: [avr-gcc-list] Re: Troubles uploading to a Mega103
Date: Fri, 30 Mar 2001 12:33:01 +0200

Hi !

> We had the same problem with both the signature bytes being 1)FF FF FF and
> being 2)00 01 02:
> 1)The ATMega103 loses its signature bytes for some reason after a few
> erase/program cycles.  The workaround is to change the UISP code.  I made a
> couple of changes already to the software already to accomodate these 
> defects (also to read/write fuse bits, correcting srec format downloads,
> etc.).  I can give you or anyone else this code if you so wish.

Ok, but why would it lose its signature bytes ? I modified Uisp to force upload/
download even if signature bytes are wrong but the flash remains filled with

Anyway, I am interested in your changes to uisp (i agree, there are some defects
to fix) and i think you should send a patch to add your changes to the official

> 2)Are you holding in the reset line using an external reset while you are
> talking to the ATMega103?  If the external reset is kept LOW the signature
> bytes will be FF FF FF when a
> "uisp -dapa" command is performed but after that the signature bytes will be
> 00 01 02 when a
> "uisp -dapa" command is performed.  Make sure the reset line is not
> externally made LOW when the UISP talks to it.

No reset is not held down. But we had /PEN (Programming Enable) connected to
the GND instead of VCC (MCU was always in programming mode)... ;) And now we
have changed it, signature bytes are always 0xffffff (except if we lock it).


Ludovic Courtès
  Université de Technologie de Belfort-Montbéliard
  Unitec (Club de Robotique de l'UTBM)

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