Quote Originally Posted by Ioannis View Post
What drives the MCLR pin of the slaves? A PIC output? ...
A tri-state general I/O pin on the master.

Output low = reset
Input = do nothing


Quote Originally Posted by Ioannis View Post
...

I am asking, because the MCLR pin needs a level of 0,2*Vdd to see LOW (for the 16F177x series, but I guess it is the same for others).

It depends on output characteristics if you are within limits of the MCLR. So be sure that what you think as low is actually sensed as low on the MCLR pins.

Ioannis
I can't say. This is all theory for now, but is supported by posts on google and a forum elder, Mr E.

So I blame him if my house burns down.