Demon,

Thank you for your advice.

Of course I did what you suggest : write a very small program and test it and that's how I found that the problem was coming from ReadCode and its execution time.
After 40 years spent in the lab I know the methodology, thanks !

I am just asking for a precise advice/recommandation to the issue I raised. In relation with ReadCode and the interrupts. Nothing else

MikeBZH