PLC PLC Communication Protocols & Networking

Question 1

Which industrial protocol uses a master/slave architecture over RS-485 serial communication and is widely supported by PLCs for connecting field devices?

Accepted Answer

Modbus RTU

Answer

EtherNet/IP

Answer

PROFINET

Answer

DeviceNet

Question 2

EtherNet/IP is based on which application-layer protocol that maps industrial objects to standard Ethernet/TCP-IP?

Accepted Answer

Common Industrial Protocol (CIP)

Answer

Modbus TCP

Answer

PROFINET IO

Answer

OPC-UA

Question 3

In PROFIBUS DP, what is the role of the 'master' device?

Accepted Answer

To initiate all data exchanges and poll slave devices for their input/output data cyclically

Answer

To provide power to all slave devices on the bus

Answer

To store the program logic for all connected PLCs

Answer

To perform address assignment for new slave devices automatically

Question 4

What is the maximum number of nodes (devices) supported on a single PROFIBUS DP segment?

Accepted Answer

126

Answer

64

Answer

256

Answer

32

Question 5

Which PLC networking protocol is specifically designed for real-time deterministic communication in motion control applications and uses a dedicated ring topology?

Accepted Answer

EtherCAT

Answer

Modbus TCP

Answer

OPC-UA

Answer

DNP3

Question 6

What does OPC-UA provide that traditional OPC (OPC Classic) did not?

Accepted Answer

Platform-independent, service-oriented communication with built-in security and no dependency on COM/DCOM

Answer

Faster polling rates for real-time I/O data

Answer

Direct programming access to PLC ladder logic

Answer

Physical layer specification for serial cabling