LIN is a broadcast serial network comprising one master and many (up to 16) slaves. No collision detection exists, therefore all messages are initiated by the master with at most one slave replying for a given message identifier.
The master is typically a moderately powerful microcontroller, whereas the slaves can be less powerful, cheaper microcontrollers or dedicated ASICs.
Current uses of LIN combine several such networks — usually with 16 nodes — all linked to a CAN upper layer...
