2. Data link layer

2.1 Track access method

The channel access method implemented in Profibus is designed to meet the requirements of industrial applications in terms of communication determinism and exchange speed, and is based on the IEEE 8802.4 bus token standard. The token circulates in a logical ring, between active stations in the direction of increasing addresses from 1 to 126 (address 0 forbidden), in the form of a frame illustrated in figure 4 . The station with the highest address (HSA: Highest Station Address) gives the token back to the station with the lowest address, thus completing a logical...