I have already said I will probably adopt the idea of using low voltage
AC source for debugging - this alone may be enough.

On reason is from a past experience were I accidentally put a TRAIC in
the wrong way around and the 5v supply that was direct of the phase
suddenly presented 230v AC to my PIC when the TRIAC burnt out (I was
using a PIC at the time), this failed then my programmer died and
finally my RS232 interface on my computer died also.

I was using a 1:1 isolating transformer in this case but phase to
neutral still present 230v when things Mr Murphy calls in to take a
look. :-(

I was worth it to see my twenty year old son jump when there was the
flash and bang lol.

But there are lots of reasons mainly to do with debugging for designs
with different power supply systems than the programmer.  

_______________________________________

Feel the power of the dark side!  
Atmel AVR

Roy Hopkins
Tauranga
New Zealand
_______________________________________


> 
> Explain me at least one good reason why you need an optoisolated
> programmer interface.
> 
> Remember you'll never need to program a microcontroller directly
> connected to power supply phase -or just to the earth- (for this job
> you could disconnect the main connection while programming and pay a
> little attention to the target design and supply )
> 
> The AN2432 from Fresscale it's a little silly one. What is more
> expensive: building a bidirectional optoisolated debugger or to use an
> 1:1 isolator transformator for the target board  while
> debugging/programming ?
> 
> Vasile

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