Networks and Communications
Frequently Asked Questions
- What is a DeviceNet network?
- How does the DeviceNet Producer/Consumer structure benefit me?
- What other benefits does DeviceNet provide?
- Who owns and manages the DeviceNet technology?
- Can I completely network all the devices in my factory on a DeviceNet link?
- How does the DeviceNet network fit into the NetLinx Architecture strategy?
- How does the DeviceNet network compare to Foundation Fieldbus as a device-level network?
- What are the top benefits of a DeviceNet network?
- The DeviceNet network provides a highly interoperable device-level network for interconnecting all of the devices in a production operation that are concerned with sensing and controlling whatever goes on in that environment.
- A DeviceNet interface adds a minimum of cost and complexity to a new or existing device.
- A DeviceNet network is a very sophisticated network with all of the built-in data quality control features that will help ensure that data and control information are accurately transmitted and received.
- A DeviceNet network supports the newest types of communication protocol that provide the most efficient communication and that support distributed control. A DeviceNet network supports Producer/Consumer type communication and Change-of-State transmission of data, for quick, efficient communication. DeviceLogix smart component technology is the first implementation of the distributed I/O that is facilitated by the Producer/Consumer operation of a DevceNet network.
- What are the biggest misconceptions about the DeviceNet network?
- Will the DeviceNet network be replaced by the EtherNet/IP network?
- What types of applications are a good fit for the DeviceNet network?
- Which companies are currently backing DeviceNet technology?
- What do you get if you select the DeviceNet network as your sensor/actuator communication system?
- An open communication standard that helps ensure multi-vendor device interoperability. DeviceNet technology provides interchangeability of "like" components from multiple vendors
- Fast, easy installation — resulting in space and time savings. The DeviceNet network helps eliminate hardwiring and its related labor and space
- Future-ready for easy additions as your needs expand and change. The DeviceNet network provides power for easy network additions
- Improved uptime through intelligent insight into device operations. The DeviceNet network alerts you to network events so you can act quickly
- Efficient bandwidth utilization through Producer/Consumer communication. The DeviceNet network efficiently uses available bandwidth so important messages always get through.
- On-the-fly configurations and additions without powering down. DeviceNet doesn't stop — even when you're adding to it.
- What is the cost comparison of a DeviceNet installation to other Fieldbus installations?
- How can I get additional information about the DeviceNet network?
A DeviceNet network is a low-cost industrial network to connect industrial devices such as limit switches, photoelectric cells, valve manifolds, motor starters, drives, and operator displays to PLC processors and PCs. The network helps eliminate expensive hard-wiring while providing device-level diagnostics.
DeviceNet is one of the world's leading device-level networks for industrial automation. In fact, more than 40 percent of end users surveyed by independent industry analysts report choosing the DeviceNet network over other networks.
The DeviceNet network offers robust, efficient data handling because it is based on Producer/Consumer technology. This modern communication model offers key capabilities that let the user effectively determine what information is needed and when.
As its name describes, DeviceNet is a fieldbus standard for device-level communication. Much more than a sensor network, DeviceNet accommodates a range of devices from drives to pushbutton stations, PLC controllers to pneumatics. Achieving this level of versatility would usually require two different fieldbuses, each with a different protocol.
Because DeviceNet is based on the Producer/Consumer model, it increases overall system performance by providing both event-based and timer-based options. Take change-of-state, for example. Using COS prevents your network from being slowed down by unnecessary message traffic. Peak network efficiency is maintained.
DeviceNet allows you to configure many products in real time over your network. You can store these configuration parameters on a PC and quickly download them if a replacement device is installed. You can even replace devices on a live network.
Probably. More than 250 companies are members of the ODVA organization, all supporting the idea of conformance testing of DeviceNet products to help ensure interoperability. These companies list more than 400 products or groups of products to help meet your automation needs.
The DeviceNet network is the foundation of the NetLinx Architecture Strategy. It was one of the first of the Producer/Consumer industrial control networks and was developed to provide the benefits of a digital network to the lowest level devices. The DeviceNet network supports the CIP protocol that is used on ControlNet and EtherNet/IP networks. The NetLinx Architecture diagram shows the type of devices typically connected to a DeviceNet network.
DeviceNet and Foundation Fieldbus networks live at the same level in the Rockwell Automation hierarchy of networks, but they live in different worlds. A primary consideration in creating Foundation Fieldbus was the need to operate in a hazardous area. It was also designed to operate over the multi-pair phone-type cables that had been installed in petrochemical plants to support 4 to 20mA. devices. At the time the Fieldbus physical layer standard was created, these two requirements dictated a low-speed network, a relatively low clock rate, and very limited current to support attached devices.
The DeviceNet network was developed to support very small devices, down to switches and pushbuttons, in the hot, electrically noisy environment of a heavy-production, discrete manufacturing factory and can supply 8A to the attached interfaces. A Fieldbus in a hazardous environment might supply 100mA, which might power 5 IS devices. A 500 KHz data rate DeviceNet network will support a maximum cable length of 100 meters, while a 31.25 KHz F ieldbus can be 1900 meters long with no repeaters.
Several of the device-level networks are not sophisticated networks. However, the DeviceNet network is very sophisticated. First, the DeviceNet network includes a CRC to guarantee that data received is correct. Second, all devices that get a transmission that is bad announce that they did not get good data. If the receiving devices complain too much, they are turned-off so they don't disable other communication on the network. Also, the DeviceNet network supports the uploading and downloading of configuration data and transmission of segmented messages when the data to be transmitted is too much for one DeviceNet message.
While it is true that a lot of the capabilities and benefits found in the DeviceNet network are included in the EtherNet/IP network, the DeviceNet network is very much alive and will be for the forseeable future. Today's costs for EtherNet/IP components cannot compete with low component and design cost for DeviceNet devices. However, as manufacturing competencies increase and drive component costs down, it will become increasingly feasible to produce device-level EtherNet/IP products.
All of the applications on any factory floor, in a warehouse, in a shipping facility, in a packaging facility, or on the machines that automate these facilities when things must be sensed and controlled are good applications for the DeviceNet network. The automation of a press or of a bottling machine or a conveyor sorting machine are good applications. Photo-electric switches, which have for years included intelligence, can report their reading and status via a DeviceNet network and get their power from the network. A Photo-electric sensor, plus a barcode reader, plus a diverter that supports DeviceLogix components can make use of many of the features that are built into a DeviceNet network.
There are more than 300 companies providing more than 350 product lines of DeviceNet products. There are many dedicated DeviceNet equipment manufacturers and integrators in all the manufacturing areas of the world. Therefore, whatever your project, you decide what your want to do and how, and then select your DeviceNet components from the best manufacturers in the world.
There are many different Fieldbus networks, and the design criteria is also very broad. Some were designed to be cheap and easy; some were designed to be deterministic; some were even focused directly on a specific industry need, e.g., Foundation Fieldbus.
The DevivceNet network is managed by the Open DeviceNet Vendor's Organization. In addition to technical descriptions of the DeviceNet network, you will find many testimonials by customers that describe their experience using the DeviceNet network.
To find out more about the Rockwell Automation DeviceNet product offerings, call 1.440.646.3NET for pre-sale information.
Since spring 2001, Rockwell Automation offers more than 450 products with built-in DeviceNet interfaces. This total includes both interface modules like the 1203-GK5 and 1203-GU6, which interface to many drives, and scanners and adapters that provide backplane interfaces to the DeviceNet network such as the 1747-SDN, 1771-SDN, 1756-DNB, 1794-ADN, 1734-ADN, and 1734-PDN.
- What is CIP, and how does it relate to the DeviceNet network?
- What tools are available to determine installation requirements, performance capabilities, and application guidelines for the DeviceNet network?
- DeviceNet Selection Guide describes many of the Rockwell Automation products including DeviceNet interfaces.
- Integrated Architecture Builder is a software product that helps you create a parts list for your DeviceNet, ControlNet, or EtherNet/IP network. This software adds features as they are developed.
- If you need additional information about products, call our Networks Presale Hotline at 440-646-3Net or send e-mail to DeviceNet Information. Or if you are installing your system, call our Technical Support Center at 440-646-6800.
- What software tools are required to set up a ControlLogix system with the I/O on the DeviceNet network and a PC for programming/configuring connected to the ControlLogix system via the EtherNet/IP network?
- What type of network topologies can I use with a DeviceNet network?
- What level of data determinism can I expect from a DeviceNet network?
- Which software tools do I need to set up a ControlLogix EtherNet/IP I/O network?
- What is the difference between the DeviceNet network and ASI?
- What type of data model does DeviceNet support?
- Multiple nodes can consume the same data from a single producer
- Nodes can be synchronized
- Optimizes bandwidth use for enhanced performance
- Protocol easily handles collection, configuration and control data over the same network
- Supports Polled, Cyclic, Change of State, and Multicast I/O data exchange
- What does a third-party company have to do to communicate with the Rockwell Automation DeviceNet Products?
CIP stands for the Common Industrial Protocol. CIP is an open protocol currently used by DeviceNet, ControlNet, and EtherNet/IP. CIP is network-independent, which means that it can be used on many different networks. CIP is the common application layer protocol that allows messages to seamlessly route from EtherNet/IP to ControlNet to DeviceNet.
Please note that the Allen-Bradley ControlLogix, PLC, and SLC platforms have used the information portion of CIP in their Ethernet products for some time. In the spring of 2001, the ControlLogix EtherNet/IP module [1756-ENET (series B)] became the first A-B EtherNet/IP product to incorporate CIP's control capability. CIP is the protocol for all Allen-Bradley networks.
Rockwell Automation offers several tools to assist you in the development of your DeviceNet system:
You need RSLogix 5000 software to program/configure the ControlLogix system. You need RSNetWorx software for DeviceNet to configure the DeviceNet devices. You need an EtherNet/IP interface card installed in your PC and a 1756-ENBT installed in the ControlLogix chassis. Use RSLinx software to connect to the EtherNet/IP network.
A DeviceNet network should be considered a bus with short drops. The features of the DeviceNet network that allow Change Of State (COS) and high performance also cause it to lose responsiveness if repeaters are used to create a major branch in the trunk.
If an application really requires multiple legs going in different directions, we suggest that you install multiple DeviceNet connections in your ControlLogix system. You can also use a ControlNet network as your system backbone with ControlNet-to-DeviceNet Linking Devices (1788-CN2DN) wherever you need to run your multiple DeviceNet networks. Or install an Ethernet/IP-to-DeviceNet bridge in a remote ControlLogix chassis.
The DeviceNet network is a deterministic network! Data is returned from a device within a specific timeframe. You can operate the network so that the data from a number of devices is recorded at one time, produced on the network as bandwidth is available, and received within the specified timeframe. When devices on a DeviceNet network are operated in the Strobe mode, they all read their inputs as soon as they get the single Strobe message. Then they send their data in order of priority.
Ordinary polling of individual nodes or configuring nodes to produce data on a cyclical basis also produces data on a deterministic basis.
The setup procedure for a ControlLogix EtherNet/IP system is very similar to a ControlLogix ControlNet setup. In both configurations, a ControlLogix EtherNet/IP module is set up using RSLogix 5000 software as a local bridge to a ControlLogix processor. From this local connection, you can add any number of remote EtherNet/IP adapters.
The primary difference between ControlNet and EtherNet/IP configuration is that you do not schedule data delivery on the EtherNet/IP network. This eliminates the need to use an RSNetWorx for EtherNet/IP product. When using an EtherNet/IP network, all network and control configuration can be performed using RSLogix 5000 and RSLinx software.
DeviceNet is a sophisticated network that supports deterministic I/O data transmission, device configuration, and explicit messaging. DeviceNet messages include 8 bytes of data and a 15-bit Cyclic Redundancy Check (CRC), which is the quality control mechanism to help guarantee that all messages received are correct. The DeviceNet network also includes sophisticated support for: Automatic Replacement of Devices, priority of data, support of Change Of State I/O, Cyclic Production of Data, and regular polling of I/O data. From this list, ASi only supports polling of I/O data.
A consortium of 12 German control and I/O equipment makers developed ASi in the early 1990s, and it's primarily used in Europe. ASi is a master/slave I/O network. It sends four bits of data per message, has no parity check, no CRC, no upload/download, no Change of State or Cyclic production of data.
It uses an inexpensive two-wire network and inexpensive taps.
The DeviceNet network follows the Producer/Consumer data model, which provides the following benefits over the traditional Client/Server or Source/Destination model:
The Producer/Consumer model is a media-independent service that supports implicit I/O and explicit information messaging simultaneously over the same wire.
Rockwell Automation products are designed and tested to be compliant with the DeviceNet specifications as owned and managed by ODVA. We encourage all manufacturers to have their devices tested and certified.
Rockwell Automation also works with a number of Value Added Design Partners (VADPs) that assist third parties in designing DeviceNet Products based on the DeviceNet Master Library. The VADPs provide all the support for the third-party developers and benefit from developments made by Rockwell Automation. This facilitates quick development of sophisticated products.