MODBUS Protocol MCQ

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MODBUS Protocol Questions and Answers

MODBUS Protocol MCQ
  1. What is the most common physical layer used for Modbus communication?

a) RS-232

b) RS-485

c) Ethernet

d) USB

Answer: b) RS-485

2. Which function code is used to read the contents of a holding register in Modbus?

a) 01

b) 02

c) 03

d) 04

Answer: d) 04

3. What is the maximum number of devices that can be connected to a single Modbus network?

a) 32

b) 64

c) 128

d) 256

Answer: d) 256

4. What is the default baud rate for Modbus RTU?

a) 9600

b) 19200

c) 38400

d) 57600

Answer: b) 19200

5. What is the maximum data payload size for a Modbus TCP packet?

a) 260 bytes

b) 512 bytes

c) 1024 bytes

d) 2048 bytes

Answer: a) 260 bytes

6. What is the Modbus function code for writing a single coil?

a) 05

b) 06

c) 15

d) 16

Answer: b) 06

7. What is the Modbus function code for reading input registers?

a) 04

b) 05

c) 06

d) 03

Answer: d) 03

8. How many data bytes can be written to a single holding register using Modbus function code 16?

a) 1

b) 2

c) 4

d) 8

Answer: b) 2

9. Is Modbus protocol a master-slave or peer-to-peer protocol?

a) Master-slave

b) Peer-to-peer

Answer: a) Master-slave

10. Which Modbus protocol variant uses ASCII character encoding?

a) Modbus RTU

b) Modbus ASCII

Answer: b) Modbus ASCII

11. Which Modbus function code is used to read the status of discrete inputs?

a) 01

b) 02

c) 03

d) 04

Answer: c) 03

12. What is the maximum number of data bytes that can be read in a single Modbus function code 03 request?

a) 1

b) 2

c) 125

d) 256

Answer: c) 125

13. How is the Modbus slave address specified in a Modbus RTU packet?

a) As a 2-byte value

b) As a single byte

c) As a 4-byte value

d) As a 6-byte value

Answer: b) As a single byte

14 . What is the default value of the transaction identifier in a Modbus TCP packet?

a) 0

b) 1

c) 2

d) 3

Answer: b) 1

15. What is the Modbus function code for writing multiple holding registers?

a) 16

b) 15

c) 14

d) 13

Answer: b) 15

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