AVR-Chat

Brian Dean wrote:

> On Fri, Nov 05, 2004 at 02:43:54PM +1100, David Jones wrote:
> 
> 
>>That's beside the point. It can and does happen.  What happens if
>>you have a soldered an AVR part on a board and lock up the ISP mode?
>>- bad news.
> 
> 
> Are you sure it is the SPIEN fuse?  According to the datasheet you
> cannot change the SPI enable fuse when actually using the ISP
> interface.  I've tried to purposefully disable it using ISP
> programming mode to no avail - it remains enabled.  I think one must
> use JTAG or high voltage parallel programming to disable the SPIEN
> fuse.
> 
> However, sometimes folks are guilty if changing the on-chip clock
> source options which can leave the chip without a working clock.  For
> example, can can set the fuse bits to select an external clock source
> when there is none.  Not as deadly as clearing the SPIEN fuse as you
> can generally feed in the needed clock and get back up and running.
> 
> It does sort've beg the question though - whey even have the option of
> disabling the SPI programming interface?
> 
> -Brian
Added Security ? IE no chance of jumping into bootloader mode etc.

Regards,

Kat.

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