Question
What is the maximum segment length allowed for PROFIBUS DP at the top bit rate of 12 Mbps?
PROFIBUSMock examPhysical layerHard
Answer
D — 100 m
At 12 Mbps the very short bit time and signal-integrity constraints cap a Type A segment at 100 m, which is the correct value. 1 200 m is wrong: that figure only applies up to 187.5 kbps. 1 000 m is wrong: that is the limit at 500 kbps. 400 m is wrong: that is the limit at 1.5 Mbps. With repeaters you can chain up to about ten segments to reach longer total lengths, but no single segment exceeds the value tied to its bit rate.
Preparation tip
Memorise the descending ladder 1200 / 1000 / 400 / 100 m matched to 187.5 k / 500 k / 1.5 M / 3–12 Mbps; it comes up in almost every PROFIBUS exam.
All proposed choices (exam context)
- A.1 200 m
- B.1 000 m
- C.400 m
- D.100 m✓
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