CAS CAS Automation Specialist Network Communications & Protocols 1

Question 1

Which industrial protocol uses a master-slave architecture over a two-wire RS-485 physical layer and is widely used for connecting PLCs to field devices?

Accepted Answer

Modbus RTU

Answer

Modbus RTU operates over RS-485 using a master-slave architecture and is one of the most prevalent serial protocols for PLC-to-field-device communication.

Question 2

EtherNet/IP uses which underlying protocol suite to transport CIP (Common Industrial Protocol) messages?

Accepted Answer

TCP/IP and UDP/IP

Answer

EtherNet/IP encapsulates CIP messages over standard TCP/IP (for explicit messaging) and UDP/IP (for implicit I/O messaging).

Question 3

What is the maximum cable length for a PROFIBUS DP network segment operating at 1.5 Mbps?

Accepted Answer

200 m

Answer

At 1.5 Mbps, PROFIBUS DP specifies a maximum segment length of 200 m; longer runs require repeaters or a lower baud rate.

Question 4

In an industrial Ethernet network, which device operates at Layer 2 of the OSI model to forward frames based on MAC addresses?

Accepted Answer

Managed switch

Answer

A managed switch operates at OSI Layer 2 (Data Link) and forwards Ethernet frames based on MAC address tables.

Question 5

HART (Highway Addressable Remote Transducer) protocol superimposes a digital signal on top of which analog signal range?

Accepted Answer

4–20 mA

Answer

HART uses FSK (Frequency Shift Keying) to overlay digital communication on the standard 4–20 mA analog current loop without disrupting the analog signal.

(CAS) Certified Automation Specialist Practice Test

(CAS) Certified Automation Specialist Practice Test

CAS CAS Automation Specialist Network Communications & Protocols 1