There are three distinct types of controller components that can be used to model controller topology:
- Terminals offer one or more connection points for sensors and/or actuators.
- Bus couplers can have terminals or other bus couplers connected to them. Like terminals, bus couplers can also have connection points (e.g. diagnostic inputs).
- Controllers have the same properties as bus couplers, i.e. they can have connection points (e.g. fast on-board IOs) and connected bus couplers. In addition, however, they have a CPU that runs control programs.
Regardless of the actual structure of the subnetwork topologies (e.g. ASI-line or SERCOS ring structure), all bus structures are modeled hierarchically during the functional configuration process (bus hierarchy).