How to select and develop a DeviceNet network:
Introduction: What is DeviceNet?
DeviceNet Characteristics
Digital/DeviceNet Benefits
DeviceNet-based Network Schematic
References
Ask the MKS Experts
DeviceNet Products from MKS Instruments
MKS DeviceNet Starter Kit
MKS Virtual Instrument Demo
Introduction
What is DeviceNet?
DeviceNet is based upon CANbus using the 11 bit identification
standard. The 11 bit identification is broken down into 5 bits for the
type (32 flavors) of messages and 6 bits for the MAC ID (64 addresses).
DeviceNet is a simple, networking solution that reduces the cost and
time to wire and install industrial devices, while providing
interchangeability of "like" components for multiple vendors.
DeviceNet is an Open Network Standard. The specification and protocol
are open. Vendors are not required to purchase hardware, software or
licensing rights to connect devices to a system. A DeviceNet Specification
can be obtained from the Open DeviceNet Vendor Association Inc. (ODVA)
DeviceNet allows the interchangeability of simple devices while making
interconnectivity of more complex devices possible.
The DeviceNet communication link is based on a broadcast-oriented,
communications protocol; the Controller Area Network (CAN). In 1996, over
10 million CAN chips were produced. There are four main CAN chip
suppliers; Intel, Motorola, Phillips and Hitachi.
DeviceNet has two primary purposes:
- Transport of control-oriented information associated with low-level devices
- Transport of other information which is indirectly related to the system being controlled, such as configuration
DeviceNet Characteristics
The list below is a summary of the Physical/Media specific
characteristics of DeviceNet:
| Bus type |
CSMA/BA, master-to-slave, explicit and solicited messaging. Unsolicited messaging, multiple masters, and peer-to-peer was introduced in early 1996 by the Systems SIG group of the ODVA for approval, conformance review and implementation in 1996 and 1997. |
| Total number of nodes |
64 |
| Bus topology |
Straight with restricted drops |
| Distance |
500 meters full trunk line, 6 meter branches @ 125 kbps
250 meters full trunk line, 6 meter branches @ 250 kbps
100 meters full trunk line, 6 meter branches @ 500 kbps
156 meters accumlative distance of the branches @ 125 kbps
78 meters accumlative distance of the branches @ 250 kbps
39 meters accumlative distance of the branches @ 500 kbps |
| Transmission media |
Full trunk line - 2 wire twisted shielded cable with 2 wire bus power cable and drain wire.
Thin trunk line - same as full above but with lesser wire size which is more economical and easier to install. |
| Transmission signal |
Square wave digital with NRZ (Non Return to Zero) encoding |
| Input bits per node |
64 bits (allocated in bytes) standard in polling mode, larger fragmented messages are supported. |
| Output bits per node |
64 bits (allocated in bytes) standard in polling mode 24 bits in explicit messaging. Fragmented messages are also supported.
|
| Speed |
125 kbps, 250 kbps, 500 kbps |
| Bus power |
8 Amp full trunk line, 4 Amp thin line |
| Duplicate address detection |
Yes, nodes announce address on start-up and all listen. If a duplicate address is heard, the duplicate node will not advance to run mode. |
| Attendance check per scan |
Yes, a list is programmed in the interface and checked |
| Error detection |
Yes, CRC |
| Error correction |
Yes, nodes that detect errors signal the sender to repeat. |
| Address settling |
Off line via hand held programmer or with a dedicated interface and host. On line via the interface master using a reserved newcomer default address that is changed to an application address. Dip/rotary switches are optional. |
| Node parameter programming |
Can be very extensive to include drive/rotational and instrument parameters |
| History |
The early days of DeviceNet were essentially Allen-Bradley. In 1992, Allen-Bradley started to share information and invite not only strategic partners, but direct competitors to become DeviceNet members. DeviceNet was released at the ICEE show in Chicago, March 1994. Then, a year later, Allen-Bradley turned DeviceNet over to ODVA, Open DeviceNet Vendors Association. |
Summary:
DeviceNet has all the ingredients for success; available silicon, a
strong, early sponsor (Allen-Bradley) to get it through development stage,
network management software, and a strong vendors group (ODVA) to refine,
promote and evolve the product.
Digital/DeviceNet Benefits
Increase design flexibility
- Provides unlimited I/O ports by providing the ability to cascade networks
- Offers instrument interoperatability and Plug & Play capabilities
Improved process data management
- Affords Peer-to-Peer or Master/Slave management
- Increased throughput and repeatability as a result of faster response to process dimensions
-Contains imbedded diagnostics, in situ calibration and proactive event and alarm notification
-In situ diagnostic can extend preventive maintenance intervals
- Reduced installation costs
- Simplified wiring translates to fewer potential fault points, less required documentation and reduces labor and space cost for wiring
DeviceNet-Based Network Schematic
For more
information on parts of this DeviceNet-based network, click on instruments
and peripherals.
*Note: Default MAC ID shipped from factory, 6,3.
References
Documents:
To request a hard copy of the following article:
"Intelligent Sensors Improve Process Control: Sensor bus technology provides access to new intelligent sensor capabilities", J. Illich,
Semiconductor International, August, 1996.
send an e-mail to MKS and ask for article Z73. Please be sure to include your full mailing address.
Ask the MKS Experts
If you have a DeviceNet-related question, you can send and e-mail
directly to our experts at MKS.
Send questions to MKS Applications Engineering. Please include your
name, company, address, phone, fax as well as your current application
along with your question. Please allow 24 hours for a response.
DeviceNet Products from MKS Instruments
MKS Instruments offers a family of products for DeviceNet
applications:
Control & Information Technology Products from MKS
i-Baratron® Digital Capacitance Manometers
Mass-Flo
Controllers
Type 683 Smart Throttle
Valve
MKS DeviceNet Starter Kit
The purpose of the MKS Instruments DeviceNet Starter Kit is to
facilitate evaluation of the MKS DeviceNet products. The Starter Kit
specification provides the customer with information to quickly order the
necessary equipment, cabling, and devices to perform a benchtop DeviceNet
demonstration and evaluation.
Overview
Equipment required:
- An IBM PC-compatible, 486 or higher with 8 Meg RAM
- An SS Technology PC-based scanner
- A +24 VDC Power Supply
- 120 Ohm 1/4 Watt Resistor (5%)
- Cabling (trunk lines/drop lines)
- MKS DeviceNet User Interface Software, (VIs)
- MKS DeviceNet components
System Layout:
The following table lists the manufacturer and part numbers for the
required materials.
| Item No. |
Description |
Manufacturer |
Part Number |
| 1 |
Mini to Conductor Cordset - 2 meter |
Turck |
RKM570-2/S630 |
| 2 |
Junction Box |
Turck |
JBBS-57-E401/S630 |
| 3 |
1 Meter Cordset (micro to micro) |
Turck |
RSCRKC573-1/S630 |
|
MKS Virtual Instrument Demo
Download a demonstration (for Windows '95 or Windows NT) of a typical
MKS DeviceNet instrument set up including software controls for:
- Baratron Pressure Transducer
- Throttle Valve
- Mass Flow Controller
- Indirect Gauges
- Convection Gauge
- Hot Cathode Ion Gauge
- Download the Demo.
- Unzip the two files (Mks_Demo.001 and Setup.exe).
- Run the Setup.exe file.
- The demo will be automatically installed, giving you the choice of where to place the files.
- Double click on the "MKS Demo" icon to launch it.
- You will see a chamber surrounded by MKS equipment. Click on any piece of MKS equipment to see the software options available.
Need help?
Contact MKS Instruments.
© 2009 by MKS Instruments