Mastering DeviceNet Industrial network protocol: Top Interview Questions and Answers – P3

1.What does the term “trunk-line/drop-line topology” signify in the context of DeviceNet?

In a trunk-line/drop-line topology, the primary communication cable, known as the trunk line, traverses the network, with individual devices connecting to it through shorter cables, referred to as drop lines.

2.Is there a maximum length limitation for the drop line in DeviceNet?

Yes, the maximum length of a drop line in DeviceNet varies based on the baud rate. For 125 kbps, it can extend up to 6 meters; for 250 kbps, it can reach up to 3 meters, and for 500 kbps, it is limited to 1 meter.

3.How does DeviceNet differ from Ethernet/IP?

DeviceNet and Ethernet/IP, despite using the Common Industrial Protocol (CIP), diverge in their physical layer technology. DeviceNet employs CAN (Controller Area Network), whereas Ethernet/IP utilizes Ethernet. They also differ in terms of speed, distance capabilities, and network infrastructure.

4.What is signified by “DeviceNet node commissioning”?

DeviceNet node commissioning denotes the process of incorporating and configuring a new node on the network, encompassing physical installation, assignment of a MAC ID, and device configuration.

5.What type of connector is typically employed for DeviceNet?

DeviceNet commonly employs a 5-pin circular connector, often recognized as a mini-style or micro-style connector. These connectors adhere to the specifications outlined in the DeviceNet standard.

6.What is the significance of ‘DeviceNet conformance testing’?

‘DeviceNet conformance testing’ is a procedure employed to confirm that a device complies with the DeviceNet standard and is fully compatible with a DeviceNet network. Such testing is typically conducted by an independent third-party testing lab.

7.What does the ‘Group 2 only’ mode entail in DeviceNet?

The ‘Group 2 only’ mode in DeviceNet pertains to the configuration of DeviceNet devices that solely require support for the Group 2 communication mechanism, which involves poll and response interactions, rather than the more intricate Group 1 (I/O) communication.

8.Can DeviceNet be employed in high-temperature environments?

DeviceNet can be used in high-temperature environments if the devices and cables used are appropriately rated for such conditions. Always consult the manufacturer’s specifications for compatibility.

9.Is it feasible to establish a wireless DeviceNet network?

Technically, it is possible to create a wireless bridge connecting different parts of a DeviceNet network using industrial wireless technology. However, this practice is not common and can introduce added complexity and potential challenges.

10.How do you select an appropriate power supply for a DeviceNet network?

To choose the right power supply for a DeviceNet network, ensure that it delivers voltage within the range of 11-25 VDC, can provide sufficient current for all network devices, and ideally includes short-circuit protection.

11.What is the procedure for adding a new device to a DeviceNet network?

To add a new device to a DeviceNet network, physically install the device, connect it to the network, set its MAC ID and baud rate (if necessary), and configure it using the network’s configuration tool.

12.How can you replace a malfunctioning device in a DeviceNet network?

To replace a malfunctioning device, remove the old one, install the new device, adjust its MAC ID to match the old one, and configure it as needed. It is expected that the program used to configure the network will recognize the new device as a suitable substitute for the previous one.

13.What measures can be taken to secure a DeviceNet network?

Ensuring the security of a DeviceNet network involves physical security for devices and network connections, network segmentation, and control over access to network configuration and management tools.

14.What is meant by “DeviceNet Safety”?

“DeviceNet Safety” is a protocol based on the standard DeviceNet but incorporates additional features for safety-critical communication. It is used in applications where reliable and fail-safe communication is essential.

15.Can devices from different manufacturers coexist on the same DeviceNet network?

Yes, as long as each device adheres to the DeviceNet standard, devices from different manufacturers can operate together on the same network.

16.How can intermittent communication issues in a DeviceNet network be diagnosed?

Troubleshooting intermittent issues can involve checking for loose or damaged connections, monitoring for electromagnetic interference, verifying power supply stability, and utilizing network analyzer tools to identify problematic patterns.

17.What factors influence the maximum length of a DeviceNet network?

The maximum length of a DeviceNet network is affected by factors such as the baud rate, cable type, and the number of devices connected.

18.Can DeviceNet networks be used in mobile applications?

Yes, DeviceNet networks can be applied in mobile settings, including vehicles and portable equipment, thanks to their robust physical layer based on the CAN bus.

19.How does DeviceNet ensure data consistency within the network?

DeviceNet employs the Producer/Consumer model to maintain data consistency. Devices that produce data (Producers) transmit it on the network, allowing any device in need of that data (Consumers) to access it, ensuring uniform and consistent data.

20.How is DeviceNet grounded?

DeviceNet should be grounded at a single point in the network to prevent ground loops. Typically, grounding is established at the power supply.

21.Is it possible to monitor data on a DeviceNet network?

Yes, data on a DeviceNet network can be monitored using tools such as network analyzers, DeviceNet monitoring software, or a PLC equipped with a DeviceNet interface.

22.What is DeviceNet QuickConnect?

DeviceNet QuickConnect is a feature that enables devices to be swiftly replaced or added to the network with minimal disruption to network communication.

23.Can a DeviceNet network be powered using Power over Ethernet (PoE)?

No, DeviceNet and PoE are distinct technologies and are not compatible. DeviceNet typically requires a separate power supply, with power supplied through the same cable used for data.

24.How can sections of a DeviceNet network be isolated?

Isolation of sections within a DeviceNet network can be achieved using repeaters or network isolators. This helps with troubleshooting, prevents faults from spreading, and can create separate voltage zones.

25.How can a loopback test be performed on a DeviceNet network?

A loopback test on a DeviceNet network can be carried out using a device that supports this function. The device sends a message to itself through the network, aiding in the verification of network functionality.

26.What type of network is DeviceNet?

DeviceNet is a digital, multi-drop network designed for connecting industrial devices, such as sensors and actuators, to PLCs and other industrial controllers.

27.What protocol does DeviceNet use?

DeviceNet uses the Common Industrial Protocol (CIP) over the Controller Area Network (CAN) as its communication protocol.

28.Why is DeviceNet considered a ‘deterministic’ network?

DeviceNet is regarded as deterministic because it provides consistent and predictable data transfer times, which are essential for real-time control in industrial applications.

29.How does DeviceNet handle collisions on the network?

DeviceNet manages network collisions using the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol. Devices check for network activity before transmitting data, reducing the likelihood of collisions.

30.How does DeviceNet handle device addressing?

Each device on a DeviceNet network is assigned a unique MAC ID (0-63), which serves as its address for communication on the network.

31.What is the purpose of the DeviceNet terminator?

The DeviceNet terminator is used at the ends of the network to match the cable’s impedance and reduce signal reflections, enhancing network reliability and performance.

32.What types of devices can be attached to a DeviceNet network?

A DeviceNet network is capable of connecting a diverse array of industrial devices, encompassing sensors, actuators, motor controllers, safety devices, I/O modules, PLCs, and more.

33.On what technology is the physical layer of DeviceNet based?

The physical layer of DeviceNet is founded on the Controller Area Network (CAN) standard, which prescribes cable types, connectors, and electrical signal levels.

34.What range of baud rates does DeviceNet support?

DeviceNet offers support for three specific baud rates: 125 kbps, 250 kbps, and 500 kbps. The actual baud rate employed depends on the network configuration and the distance over which data is transmitted.

35.What is the significance of MAC IDs within DeviceNet?

MAC IDs serve as unique identifiers assigned to each device connected to a DeviceNet network, enabling the network master to individually address and communicate with each device.

36.How is power distribution managed in a DeviceNet network?

Typically, power distribution in a DeviceNet network occurs through the same trunk cable that carries data. Among the five conductors in the cable, two are designated for power transmission.

37.What is a DeviceNet master’s main purpose?

The primary responsibility of a DeviceNet master, often embodied by a Programmable Logic Controller (PLC), is to oversee and regulate data flow within the network. This includes initiating communications and managing the network’s scheduling.