Unless you are 100% orchestrated by a master station, then you need a contention protocol... (for peer to peer structures).

Its what to do when transmitters take the line at the same time and attempt to reserve the channel for a slot. Usually assigned or random delays before re-attempting channel grab is used.

It depends upon the information flow whether peer-to-peer is worth bothering with. It can be very good for nets doing exception reporting.

But I think all would agree a channel master approach is easier for beginners. Usually a token sharing approach is used wherein the master polls each slave device in order to inquire if they have any news to report or to deliver commands from the master to the slave. The polling does make for constant chatter on the line, but if you require slaves to respond to polling then you'll know quickly when one goes down.

aka j