CPE Profibus Network Architecture & Design 2 — Questions and Answers
Question 1: What is the maximum number of stations (including repeaters) allowed on a single Profibus DP segment?
- 16
- 32 (Correct answer)
- 64
- 126
Correct answer: 32
A single Profibus DP segment supports a maximum of 32 stations, including the repeater if used.
Question 2: Which Profibus DP topology supports the longest cable runs at 9.6 kbps?
- Star topology
- Ring topology
- Bus (line) topology (Correct answer)
- Tree topology
Correct answer: Bus (line) topology
Profibus DP uses a bus (line) topology as its standard configuration, and at 9.6 kbps allows cable segments up to 1200 meters.
Question 3: In a Profibus DP network, what role does the Class 2 master (DPM2) serve?
- Controls cyclic data exchange with slaves
- Provides engineering and diagnostic functions (Correct answer)
- Acts as a bus terminator
- Bridges two network segments
Correct answer: Provides engineering and diagnostic functions
The Class 2 master (DPM2) is used for configuration, commissioning, and diagnostic purposes rather than cyclic I/O control.
Question 4: When cascading Profibus DP repeaters, what is the maximum number of repeaters that can be connected in series?
- 2
- 3
- 5
- 9 (Correct answer)
Correct answer: 9
Up to 9 repeaters can be cascaded in series on a Profibus DP network, allowing extension of both distance and station count.
Question 5: Which Profibus DP GSD file parameter defines the maximum permissible response time for a slave device?
- Min_Slave_Intervall
- Freeze_Mode_supp
- Watchdog_Fact
- MaxTsdr (Correct answer)
Correct answer: MaxTsdr
MaxTsdr (Maximum Slave Data Response time) in the GSD file specifies the maximum time a slave may take to respond to a master request.
Question 6: What happens on a Profibus DP network if a slave does not respond within the watchdog timeout period?
- The master skips to the next token
- The slave is marked as failed and outputs go to a safe state (Correct answer)
- The network resets all stations
- The baud rate is automatically reduced
Correct answer: The slave is marked as failed and outputs go to a safe state
If a slave's watchdog timer expires (no valid master communication received), the slave transitions to a safe state and sets its outputs accordingly.
Question 7: In Profibus DP, which transmission medium is used in the RS-485 physical layer standard?
- Coaxial cable
- Twisted pair shielded cable (Correct answer)
- Fiber optic only
- Unshielded twisted pair (UTP)
Correct answer: Twisted pair shielded cable
Profibus RS-485 uses a shielded twisted pair cable (STP) as its standard transmission medium to reduce electromagnetic interference.
CPE Profibus Network Architecture & Design 2
What is the maximum number of stations (including repeaters) allowed on a single Profibus DP segment?