Principle of Operation: K-Bus
The K-Bus system is primarily an event-driven system. Messages are sent after a request has been made for component operation or status change.
Each of the K-Bus users are continually monitoring messages on the system. When a user needs to transmit, it waits until there is no activity and then transmits its message. The sender then listens to the system for its own message to be returned by the receiver. If it doesn't receive its own message, a user with higher priority has also transmitted and its message was ignored. The lower priority user then has to wait until the bus becomes inactive and retransmits. When it receives its own message back (correctly) successful transmission is confirmed.
All control units on the K-Bus receive all messages, but only the module addressed in the message will accept and react to the data.
The K-Bus remains operational in the event of a disconnected or failed control unit. This parallel circuit is referred to as a "Tree" structure with each control unit occupying a branch.
The K-Bus provides the diagnostic connection to the control units located on the bus (except for the IKE).
Rules for operation:
- Only one module speaks at a time (serial communication).
- Everybody speaks at the same speed.
- Messages are acknowledged by the recipient.
- The message is repeated if the addressed module fails to respond.
- The BC1 has priority.
- Quit sending message after 5 failed attempts.