A bus is a Common communication system for data transmission between several devices or participants via a common transmission path. Several devices can be connected to this transmission path - for example a line or a cable system - which exchange data via defined communication rules.
Since all participants share the same transmission path, the only one device is actively transmitting at any one time, while the other participants listen. To avoid conflicts and enable orderly data exchange, access to the bus is restricted by defined Bus access procedure regulated.
Typical procedures include, for example
- Master-slave principle: A central device (master) controls the communication and queries the connected participants (slaves) one after the other.
- Multi-master principle: Several devices can start communication processes independently; a collision avoidance mechanism regulates access to the bus.
- Token passing procedure: A virtual „token“ is passed on from participant to participant; only the participant who has the token may send.
During communication, other subscribers can view the data traffic read along passively, without actively participating in it themselves. This form of eavesdropping is often referred to as Sniffing and is used, for example, for Diagnosis, analysis or troubleshooting used.
In the industrial automation and measurement technology bus systems are often used to efficiently network sensors, actuators, controllers and measurement data acquisition systems. Typical examples are fieldbus and industrial communication systems that enable structured and reliable data transmission between many devices.