The SERCOS network uses which topology?

• A. Ring
• B. Star
• C. Bus
• D. Mesh

Answer: (A)

Ring topology enables deterministic, cyclic data exchange in SERCOS. In the traditional SERCOS I setup, a master initiates a fixed-cycle frame that travels around a closed loop through each device in sequence. Each device has a reserved slot to write its output and read input data as the frame passes, and the frame returns to the master to start the next cycle. This single circulating frame eliminates data contention and gives a guaranteed update rate and fixed latency, which is essential for real-time control of multiple drives and I/O.

Star, bus, or mesh topologies would introduce unpredictable delays or require complex arbitration and switching, which undermines the precise timing SERCOS aims to provide. (Note: SERCOS III uses real-time Ethernet, which can use switched Ethernet topologies, but the classic SERCOS I network is ring.)