Rockwell Automation DeviceNet Selection Guide

Introduction to DeviceNet

DeviceNet is a low-cost communication link to connect industrial devices (such as limit switches, photoelectric sensors, valve manifolds, motor starters, push buttons, bar code readers, variable frequency drives, panel displays, and operator interfaces) to a network and eliminate time-consuming and costly hard wiring. A DeviceNet network is positioned on the device level of a network hierarchy. This allows for a reduction in wiring and installation costs. The direct connectivity provides improved communication between devices as well as important device-level diagnostics not easily accessible or available through hard wired I/O interfaces.

The NetLinx™ Philosophy

The future demands advanced network technology, greater system performance, and higher productivity. Rockwell Automation has designed a common communication protocol and interfaces for networks that connect the plant-floor device all the way to the Internet. This architecture, referred to as NetLinx, takes advantage of readily available producer/consumer networking services and standard hardware and software interfaces. The NetLinx architecture brings you advanced communication features, flexibility, and performance when you need them.

Rockwell Automation brings you Rockwell Software and Allen-Bradley brand products that work with the NetLinx open network architecture, consisting of the EtherNet/IP, ControlNet, and DeviceNet networks. The ability to integrate these networks together into a system offers these benefits:

• networks that are best suited to an application
• a common architecture for control, configuration and collection of plant-floor information
• the ability to control, configure, and collect data on the same network
• seamless integration between networks due to the common NetLinx architecture
• data accessibility to all devices--any time, any place
• improved system performance and lower total cost of ownership

Producer/Consumer and DeviceNet

The DeviceNet network is based on the producer/consumer network model, the latest in network technology. This technology allows for real-time control data exchange, configuration capabilities exclusive from control performance, and collection of data at regular intervals or on-demand.

Producer/consumer is better because:

• multiple nodes can consume the same data at the same time from a single producer
• nodes can be easily synchronized for more precise system performance
• devices can communicate autonomously--no need for a system master

On producer/consumer networks, packets are identified by content rather than an explicit destination. If a node needs the packet, it will accept the identifier and consume the packet. So the source sends that packet once and all the nodes consume the same packet if they need it. This breakthrough brings you:

• increased efficiency because data is produced once, regardless of the number of consumers
• precise synchronization because data arrives at each node at the same time

Using this Publication to Plan Your Network

This publication is designed to help you plan your DeviceNet network. Basically, you will do this using five steps. These steps are:

1. Laying out your system, based on your requirements
2. Placing your required devices into definable groups, or identifying how you can cluster your devices
3. Determining your network components
4. Choosing your platform
5. Recording your choices in a bill of materials

This publication is divided into sections to assist you with choosing DeviceNet system components. To understand how to use this publication, refer to the tabbed chart on page 17.

Laying Out Your System

The most important items for this first step are a pencil and paper. When you begin network planning, it is best to simply start by drawing up a sketch of your future network. When doing so, ask yourself these questions:

• What type of devices do I need? (Example: sensors, actuators, controllers, drives, operator interfaces)
• What will be the approximate distances between devices, and where will they be physically located?
• How many inputs/outputs do I need? Label all of the devices and distances in your drawing. By keeping your sketch detailed, you will be able to select devices more easily later on in the network development process.

Types of DeviceNet Systems

All Rockwell Automation controller interfaces on DeviceNet provide mechanisms for data sharing with other controllers. Because DeviceNet follows the producer/consumer model, it makes data accessible to every component of the system, simultaneously, providing more efficient use of network bandwidth. This gives you network set-up flexibility. You can set-up your network for master/slave, multi-master/slave, peer-to-peer or any combination.

Traditionally, networks are set up in master/slave mode. Master devices (typically PLCs) are used to control secondary devices (slave devices). On a communication link, it is the master device that can initiate communication. Slave devices, therefore, are the devices that collect the command messages from a master device. Unlike master devices, slave devices cannot initiate any form of command messages. They simply reply to the messages sent from the master.

In a master/slave situation, a master controller sends output command messages one at a time to the slave devices on the network, which reply with input status messages.

Multi-master/slave mode can be configured as follows:

• you can have an unlimited number of masters in a system
• a master can act as a slave to another master

You can choose this configuration to take advantage of DeviceNet's flexibility over traditional networks in implementing master/slave and peer-to-peer communication.

In a multi-master situation, master controllers can send command messages, as well as become slave devices to other controllers.

Peer-to-peer configurations allow messages to be exchanged between devices on an equal basis. Unlike master/slave mode, peer-to-peer allows any device to initiate communication with another device when it has the need to communicate.

In a peer-to-peer situation, devices can share data between each other equally.

Placing Devices into Definable Groups

The second step toward building your network is recognizing the groups of devices you will be using. For example, if you require photoelectric sensors and limit switches, you could group these two device types into one group called sensors. Another example is creating an operator interfaces group which could include tower lights, hand-held configurators, and electronic operator interfaces. By creating groups such as these, you will be better able to find the devices you need in this publication, and in other DeviceNet publications.

Determining Your Network Components

This publication is your tool for selecting Rockwell Automation DeviceNet products. At this point, you can use your network sketch, and defined device groups to search through this publication for the appropriate DeviceNet devices.

The DeviceNet Assistant software provides you with a graphical representation of your DeviceNet network as you choose your network components. You can use this helpful software with this publication for a detailed look at your future network. A free download of the software is located at: http://www.ab.com/networks/assistant/.

You will determine which network devices you need based on a few criteria. Listed below are some items you may want to consider.

• Costs/acquisition costs
• Installation costs and logistics
• Diagnostic needs
• Smart devices vs. I/O
• Open-style or sealed devices
• Round vs. flat media

Here are specific questions which will help you determine what type of network your application needs, and which components will help you build that network.

1. What type of DeviceNet system are you planning?

All Rockwell Automation controller interfaces on DeviceNet provide mechanisms for data sharing with other controllers.

Input data can be shared by controllers.

2. Are you planning on using classic I/O devices, smart I/O devices or a mix?

• Classic I/O: Acquisition costs are lower, Number of nodes per network is lower, Diagnostics are minimal
• Smart I/O Devices: Diagnostics and data from devices increases, Hardwiring is minimal, Life-cycle is lower due to preserved uptime

A Word About I/O Messaging

Leveraging the producer/consumer model, DeviceNet allows you to select between four methods of I/O exchange on a per-device basis:

• Cyclic: Ideal for precise data delivery at specific rates (e.g., 10 ms, 50 ms, 200 ms). Appropriate for devices with slowly changing data.
• Change-of-state (COS): Sends data only when there is a change in the device's state. Supports a "heartbeat" for status updates.
• Polled: Traditional method where a master device asks a slave device for data.
• Strobed (Multicast): Allows master devices to gather input status from multiple DeviceNet slave devices quickly by generating one data message delivered to multiple devices simultaneously.

Input data can be shared between multiple controllers, improving system performance and synchronization. Output data must come from only one controller.

3. What type of physical media do you plan to use?

Round Media: Consists of two twisted pair wires (power and signal) plus drain. Available in thick (12 mm) and thin (7 mm) sizes. Typically used when distances are known and fixed, greater overall distance is required, or daisy-chaining without droplines is preferred.

Flat Media: Consists of two pair wires (power and signal). Typically used when distances are less known or may change, wiring is performed on-site, or future additions are anticipated.

Physical Media Specifications:

• Thick Media: Max Current: 8 Amps. NEC Class 2: 4A. Gray PVC jacket, mylar tape, 65% tinned copper-braid shield.
• Thin Media: Max Current: 3 Amps. Yellow chemical resistant CPE jacket, mylar tape, 65% tinned copper-braid shield.
• Flat Media: Max Current: 8 Amps. NEC Class 2: 4 Amps. Various jacket materials (TPE, PVC).

Data Rates and Distances: DeviceNet operates at 125Kb, 250Kb, and 500Kb. Maximum trunk length depends on data rate and cable type. Drop lines are limited to 6 meters (20 ft) each.

Power: DeviceNet includes a power pair (24V dc) for device transceivers and some devices can use it as their power source. Current draw dictates the number and size of power supplies needed.

4. What type of connections do you need for the environment your network is in?

• Sealed: Perfect for devices exposed to the environment, offering time and installation savings, and reduced risk of miswiring.
• Open-Style: Used for in-panel devices, offering acquisition cost savings and good for simple daisy-chaining.

Unsealed and sealed connectors can be mixed on the same system.

5. Are you planning a stand-alone DeviceNet network, or one that is part of a larger architecture?

6. Do you desire bridging capabilities to other networks, such as EtherNet/IP, Data Highway Plus, DH-485, or ControlNet?

Rockwell Automation solutions include ControlLogix, RSLinx Gateway, and the ControlNet to DeviceNet Linking Device.

Selecting RSNetWorx Software for DeviceNet Configuration

You need RSNetWorx for DeviceNet to configure parameters and commission nodes. RSNetWorx uses Electronic Data Sheet (EDS) files to understand device capabilities. EDS files can be downloaded from www.ab.com/Networks/eds.

Catalog Number: 9357-DNETL3

Choosing Your Platforms

This publication provides a diagram to help navigate through product families. Each component type is matched with corresponding tabbed section labels for product families. Reading the introduction to each product family is recommended for choosing appropriate devices.

Recording Your Choices in a Bill of Materials

The final step is to select devices and record their catalog information in the bill of materials form. Fax or send the completed form to a Rockwell Automation sales office or distributor.

Additional DeviceNet Features

• Automatic Device Replacement (ADR): Device configurations stored centrally allow for automatic download to a replacement device, minimizing downtime.
• Autobaud: Device automatically configures its data rate (125Kb, 250Kb, or 500Kb) when connected to an existing network.
• Configuration Consistency Value: Allows comparison of stored configuration with the device's configuration for system audits.
• Faulted Address Recovery: Devices can remain in an "inactive" state when a node address is duplicated, allowing reconfiguration over the network.
• Auto-search for Vacant Address: Device searches for an unused node address upon connection.

Tools for Designing Your Network

Rockwell Automation provides tools such as starter kits, hands-on seminars, and training classes to assist in building and maintaining DeviceNet systems.

DeviceNet on the Web

The Rockwell Automation Networks website (www.ab.com/networks) offers up-to-date information on DeviceNet, ControlNet, and EtherNet/IP, including EDS files, new products, developer information, and case studies. The DeviceNet Assistant software, available for download, aids in network planning and organization.

Product Categories

This guide covers a range of Rockwell Automation DeviceNet-compatible products:

• PC-based Controllers: PCI bus and CompactPCI bus scanner cards for PC integration.
• PLC/SLC/Logix-based Controllers: Interface modules and scanner modules for Allen-Bradley controllers.
• Linking Devices: Modules for inter-network data exchange, such as ControlNet to DeviceNet.
• I/O - Packaged: Compact and cost-effective I/O solutions like ArmorBlock MaXum and CompactBlock I/O.
• I/O - Modular: Flexible and scalable systems like FLEX I/O, FLEX Integra, POINT I/O, and Compact I/O.
• Sensors: Photoelectric and inductive proximity sensors, and limit switches with DeviceNet connectivity.
• Operator Interfaces: PanelView terminals, stack lights, push button stations, and pendant stations for human-machine interaction.
• Power and Energy Management Solutions: Powermonitor II and Powermonitor 3000 for power system monitoring.
• Motor Starters and Protectors: Distributed Starter Systems (DSA), E3 Solid-State Overload Relays, SMC Dialog Plus, and Smart Motor Managers.
• Drives: Various AC and DC drives with DeviceNet communication options. (Details not fully transcribed due to length).
• Motion Control: Systems for motion control with DeviceNet capabilities. (Details not fully transcribed due to length).
• PC Interfaces: Communication interface cards for PCs. (Details not fully transcribed due to length).
• Physical Media: DeviceNet cabling and accessories. (Details not fully transcribed due to length).