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:
The list below is a summary of the Physical/Media specific characteristics of DeviceNet:
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
Straight with restricted drops
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
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.
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.
125 kbps, 250 kbps, 500 kbps
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
Yes, nodes that detect errors signal the sender to repeat.
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
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.
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.
Increase design flexibility
Improved process data management
MKS Instruments, Inc.
Dearborn Group Technology
Allen-Bradley Company, Inc.