Practice Test Geeks(CAS) Certified Automation Specialist Practice Test
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CAS Automation Specialist Network Communications & Protocols Flashcards

7 cards from real CAS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  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?

    Answer: Modbus RTU

    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.

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

    Answer: TCP/IP and UDP/IP

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

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

    Answer: 200 m

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

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

    Answer: Managed switch

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

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

    Answer: 4–20 mA

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

  6. Which network topology is most commonly used in PROFINET IO for its simplicity and ease of troubleshooting?

    Answer: Star

    Star topology is most common in PROFINET IO, with all devices connected to a central managed switch, making fault isolation straightforward.

  7. What is the primary function of the OPC UA (Unified Architecture) standard in industrial automation networks?

    Answer: Platform-independent, secure data exchange between automation systems

    OPC UA provides a vendor-neutral, platform-independent framework for secure and reliable data exchange between industrial devices and enterprise systems.