Re[2]: [avr-gcc-list] Lock bits

[interia]

Hello,

Tuesday, January 4, 2005, 9:26:23 PM, you wrote:

GD> "Larry Barello" wrote:

>> More likely, however, is that you accidentally selected an external clock
>> option which effectively kills the chip.

GD> The OP said "[I] can also use JTAG".  Messing up the clock fuses does not
GD> prevent the JTAG interface from working.  You can set another clock mode
GD> with a JTAG interface and recover.  This is because it uses its own clock
GD> and does not need the main MCU clock to run.  This is not documented, but
GD> Atmel have confirmed that it is so.

GD> However, the OP also talks explicitly about lock bits and not fuses.  He
GD> does not say whether or not the fuses are messed up as well.  It should be
GD> possible to erase the chip and clear the lock bits with either the SPI or
GD> JTAG interfaces.  I have certainly done this, though not specifically with
GD> an ATmega128.  He reports that this does not work.  This could be explained
GD> by both the SPI and JTAG interfaces being disabled, in which case, yes,
GD> parallel programming seems the only way out.

GD> Graham.

 I looked into datasheet and found that the only way to clear lock
 bits is "chip erase" command in parallel programming mode with +12V
 supply applied to /RESET pin. There's been no problem with clocking because I 
had to use external clock
 when I was checking Configuration and Security bits. Thanks Larry.

 Daniel Kica                           mailto:address@hidden



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