Salutations de Hong Kong Alain!

I'll continue in English so that this may eventually help others...

1) The hardware side : system must be in a stable safety state if Processor is out of its socket ( ! ) - @ poweron all pins are inputs ( floating ...)

Got it!, Yep! the system would be stable even without a processor in socket. I've got pull down on all lines that I want to power up in low state.

2) The software side : processor outputs must meet 1) ( no change !!! ) and inputs must be set to the state the sensors and buttons are in 1) situation, so no uncontrolled change could occur.

PORT or LAT Registers have to be set first, THEN TRIS registers ...

Oups... I'm doing the opposite. I first set Tris, then assign them low or high... Could that really cause the problem?

That's enough to be perfect !!!

Thanks for your help!

Patrice