I get what you say ! I'll try to change this especially that I don't want to paralyse the bus when I will be working on many arduino slaves.
What's the purpose of this project?
Actually, it's for simulation purpose. I have log files containing simulation data. I need that data in my arduinos.
I would use SD cards to store each data type on an arduino however, since they cannot be synchronized, they don't have the same clock : this can't be done because the diffrent arduinos data are semantically dependent.
So I'm trying to make the PC pilot the simulation using its own clock and each time an arduino needs data it asks for it from the PC.
That's the origin of the idea.
I would give up this solution if found a way to make different arduinos synchronised : start exactly at the same time and have the same clock, or parse files at the same speed with no shift between them.