An Overview of Open DeviceNet Vendor Association PMB 499, 20423 State Road 7 #F6 Boca Raton, FL...
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Transcript of An Overview of Open DeviceNet Vendor Association PMB 499, 20423 State Road 7 #F6 Boca Raton, FL...
An Overview of
Open DeviceNet Vendor Association
PMB 499, 20423 State Road 7 #F6
Boca Raton, FL 33498 USA
©1998, 1999 ODVAAn Overview of
DeviceNet is Positioned at the Device Level
©1998, 1999 ODVAAn Overview of
Network Layer Positioning-
F
un
cti
on
alit
y
+ Information Level Network
Automation & Control Level Network
Device Level Network
- Cost +
+ C
om
ple
xity -
- Data +
Discrete Process
I/O Control Peer-to-Peer
Sensor Actuator Level
Network
©1998, 1999 ODVAAn Overview of
Network Positioning-
F
un
cti
on
alit
y
+
EtherNet/IP
- Cost +
+ C
om
ple
xity -
- Data +
DeviceNetOther CANSDS
Fieldbus H1Profibus-PAModbusHART
Profibus-DPInterbus-SRemote I/O
Profibus-FMSData Highway+Modbus Plus
ASi, Seriplex, Hardwiring, RS485 etc.
ControlNetFoundation Fieldbus H2
©1998, 1999 ODVAAn Overview of
History & Technology
History Base Technology
developed by Allen-Bradley
Introduced March, 1994
Technology transferred to ODVA in April, 1995
Technology CAN messaging
layer 2 (data link layer) - ISO 11898 and 11519-1
DeviceNet is layer 7 (application layer ) and layer 1 (physical layer) designed for industrial automation
©1998, 1999 ODVAAn Overview of
Key Benefits
Reduced Wiring and Installation Cost Reduced Start-Up Time Reduced Downtime Removal, insertion and replacement of devices on the
network under power Interchangeability of devices from multiple vendors Rapid Troubleshooting Efficient Communication Configuration of devices over the network (set-up or runtime)
©1998, 1999 ODVAAn Overview of
Reduced Wiring and Installation Cost
“DeviceNet eliminates the need to run long stretches of wire or conduit.” Steve Jessup, Maintenance Manager
Rhode Island Beverage
Before DeviceNet After DeviceNet
©1998, 1999 ODVAAn Overview of
Reduced Start-Up Time
“We had lead times of 22-24 weeks for getting a production line up-and-running. With DeviceNet, we’re down to 5-6 weeks.” Jeff Kornetzke, Systems Manager
Planar Standish, Inc.
©1998, 1999 ODVAAn Overview of
Reduced Downtime
“Using DeviceNet provides valuable diagnostic information to help diagnose and troubleshoot problems before they occur.” Jeff Danielson, Lead Electrician
Black Hills Bentonite
©1998, 1999 ODVAAn Overview of
Removal and InsertionUnder Power (RIUP)
“DeviceNet provides us with increased flexibility. As we expand, we can add or remove devices from the system without powering down.”
Dominique Alibeckoff,Director of EngineeringNylonge
©1998, 1999 ODVAAn Overview of
Interchangeability of Devices From Multiple Vendors
“DeviceNet products are virtually interchangeable because of the network’s Device Profiles.”
Gary Workman, Staff Development EngineerGeneral Motors
©1998, 1999 ODVAAn Overview of
Rapid Troubleshooting
“If we have a problem on a production line, DeviceNet provides a fast and accurate diagnosis -- reducing the time needed for maintenance and troubleshooting.”
Rick Teeny, PresidentTeeny Foods
©1998, 1999 ODVAAn Overview of
Efficient Communication
“DeviceNet is a giant step forward in making plant floor information available in real time because it provides faster data processing, more security in data transmission, superior error checking and greater overall flexibility.”
Michael Kreller, General ManagerPriority One Packaging
©1998, 1999 ODVAAn Overview of
Configuration of Devices Over the Network
“DeviceNet is the only network that enables us to dynamically add and subtract nodes without network re-configuration.”
Mark Bauwens, EngineerCheesebrough Ponds
©1998, 1999 ODVAAn Overview of
Wide Selection of Products
“Because of DeviceNet’s interoperability, we were able to choose best-in-class products at the lowest cost. In fact, our line features more than 60 devices from seven different DeviceNet suppliers.”
Brian Gile, EngineerRaynor Garage Doors
Additional Benefits
©1998, 1999 ODVAAn Overview of
Ease of Use
“DeviceNet allows us to access information such as line faults and drive parameters from a single operator terminal.”
Ron Schiepan, Packaging SupervisorLabatt Breweries
©1998, 1999 ODVAAn Overview of
Reduced Time and Effort
“DeviceNet has saved us hundreds of hours because we can store presets for our devices.”
Gregory Amos, Director of Systems EngineeringRemstar International Inc.
©1998, 1999 ODVAAn Overview of
Other Feedback
“The smallest definable block used with our proprietary network was 32 inputs and outputs, but with DeviceNet we were able to cut it down to only four inputs and outputs.”
– Phil Hamilton, Engineer,Seed & Grain Systems, Inc.
“With DeviceNet’s simple plug connectors, we see a definite savings in both time and effort.”
– Bill Ripley, Controls Engineer, Food Machinery Sales
“DeviceNet eliminated wiring, reduced costs, and improved noise immunity. Its performance was essential in getting us to our final prototype.”
– Mike Macdonald, Executive Vice President, International Submarine Engineering Ltd.
©1998, 1999 ODVAAn Overview of
Linear Bus Topology(Trunkline-Dropline)
NodeNodeNodeNode
NodeNodeNodeNodeNodeNodeNodeNode
NodeNodeNodeNode
NodeNodeNodeNode NodeNodeNodeNode
NodeNodeNodeNode NodeNodeNodeNode NodeNodeNodeNode
Power (24Vdc, 8A) & Signal to Power (24Vdc, 8A) & Signal to all devices on a single cableall devices on a single cable
Drop length: 0 - 6 metersDrop length: 0 - 6 meters
Branching & Daisy-ChainBranching & Daisy-Chain
©1998, 1999 ODVAAn Overview of
Network Specifications
CumulativeDrop-line Budget156m @ 125Kbaud 78m @ 250Kbaud 39m @ 500Kbaud(Maximum of 6m each)
Trunk line Distanceand Baud rate100m Max. with Thin cable500m @ 125Kbaud (thick)250m @ 250Kbaud (thick)100m @ 500Kbaud (thick)(4Km with Repeaters)
Maximum Devices64 Nodes per Network
Physical Media(Shielded Twisted Pair)Communications and Power•Thick - Trunk wire•Thin - Trunk or Drop
Drop-line wiring•Single drop•Daisy-chaining off drop•Branching off drop
Device ConnectionsT-TapsZero-drop
Terminating Resistors75 Resistors at bothnetwork trunkline ends
Network Power•24vDC power to devices•Thick trunk rated to 8 amps•Thin wire rated at 3 amps
Messaging ServicesProducer/Consumer•High-speed I/O•Programming•Configuration•Diagnostics
ALLEN-BRADLEY
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©1998, 1999 ODVAAn Overview of
Network Messaging Services
Multi-master
Cyclic
StrobeChange-of-State
Multicast
Point-to-Point
Peer to Peer
Polling
Broadcast
ALLEN-BRADLEY
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©1998, 1999 ODVAAn Overview of
Polled I/O Messaging
CTLR1CTLR1 HMIHMI
Drive1Drive1SensorSensor Drive3Drive3Drive2Drive2
ALLEN-BRADLEY
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Polling
CTLR2CTLR2
©1998, 1999 ODVAAn Overview of
Strobe I/O Messaging
CTLR1CTLR1 HMIHMI
Drive1Drive1SensorSensor Drive3Drive3Drive2Drive2
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Strobe
CTLR2CTLR2
©1998, 1999 ODVAAn Overview of
Change-of-State I/O Messaging
CTLR1CTLR1 HMIHMI
Drive1Drive1SensorSensor Drive3Drive3Drive2Drive2
CTLR2CTLR2ALLEN-BRADLEY
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Change-of-State
©1998, 1999 ODVAAn Overview of
Cyclic I/O Messaging
CTLR1CTLR1 HMIHMI
Drive1Drive1TemperatureTemperature
SensorSensor Drive3Drive3Drive2Drive2
ALLEN-BRADLEY
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Cyclic
Cyclic Rate100ms
Cyclic Rate200ms
Cyclic Rate50ms
Cyclic Rate25ms
CTLR2CTLR2
©1998, 1999 ODVAAn Overview of
Point-to-point Messaging
CTLR1CTLR1 HMIHMI
Drive1Drive1SensorSensor Drive3Drive3Drive2Drive2
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1 2 3
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Point-to-Point
CTLR2CTLR2
©1998, 1999 ODVAAn Overview of
Multi-master Messaging
CTLR1CTLR1 HMIHMI
Drive1Drive1SensorSensor Drive3Drive3Drive2Drive2
ALLEN-BRADLEY
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Multi-master
CTLR2CTLR2
©1998, 1999 ODVAAn Overview of
Multi-cast I/O Messaging
CTLR1CTLR1 HMIHMI
Drive1Drive1SensorSensor Drive3Drive3Drive2Drive2
ALLEN-BRADLEY
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4 5 6
1 2 3
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Multicast
CTLR2CTLR2
©1998, 1999 ODVAAn Overview of
Broadcast
CTLR1CTLR1 HMIHMI
Drive1Drive1SensorSensor Drive3Drive3Drive2Drive2
ALLEN-BRADLEY
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4 5 6
1 2 3
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Broadcast I/O Messaging
CTLR2CTLR2
©1998, 1999 ODVAAn Overview of
Peer to Peer
CTLR1CTLR1 HMIHMI
Drive1Drive1SensorSensor Drive3Drive3Drive2Drive2
CTLR2CTLR2
ALLEN-BRADLEY
7 8 9
4 5 6
1 2 3
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Peer-to-Peer I/O Messaging
©1998, 1999 ODVAAn Overview of
CTLR1CTLR1 HMIHMI
Drive1Drive1SensorSensor Drive3Drive3Drive2Drive2
CTLR2CTLR2
ALLEN-BRADLEY
7 8 9
4 5 6
1 2 3
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Hybrid I/O Messaging
Multi-master
Cyclic
StrobeChange-of-State
Multicast
Point-to-PointPeer to Peer
Polling
Broadcast
©1998, 1999 ODVAAn Overview of
Typical Sealed-Style Physical Media
Multiport Taps
Tee Taps
Trunk line segments -molded mini-connectors
Drop lines - molded connectors - 0 to 20 ft. - mini or micro at device
Field Installabletrunk lineconnectors
NodeNodeNodeNode
NodeNodeNodeNode
NodeNodeNodeNode
NodeNodeNodeNode
NodeNodeNodeNode
NodeNodeNodeNode
NodeNodeNodeNode
NodeNodeNodeNode
NodeNodeNodeNode
©1998, 1999 ODVAAn Overview of
Typical Open-Style Physical Media
Zero drop with temporary terminalsupport Taps may be mounted in panels or
in junction boxes with cord grips
TrunkTrunk
Droplines (0-6 m)Droplines
NodeNodeNodeNode
NodeNodeNodeNode
NodeNodeNodeNode
NodeNodeNodeNode
NodeNodeNodeNode
NodeNodeNodeNode
NodeNodeNodeNode
NodeNodeNodeNode
NodeNodeNodeNode
©1998, 1999 ODVAAn Overview of
IDC Module Tap& Flat Wire
Module Top
Flat Media with Insulation Displacement Connectors
Two retentive screws for driving blades through cable
“Snap-on” connection
Mechanically-keyed4-wire flat cable
Four through-holes(only two shown) for mounting entire assembly
©1998, 1999 ODVAAn Overview of
CAN (Controller Area Network) CAN is open technology supporting multiple applications Chips available today from multiple suppliers
Intel, Motorola, Philips/Signetics, NEC, Hitachi, Siemens
Volumes from multiple industry usage insures downward price pressure
over 97 million chips sold in 1998 over 137 million forecasted by 2000 (CAN in Automation) 100 to 10,000 times the volume of other industrial ASICs
Currently in use in automobile environment today an excellent proxy for industrial applications temperature extremes, high noise environment used in critical control loops (ABS braking)
©1998, 1999 ODVAAn Overview of
CAN Sales 1997-2002
173
149
137
123
97
60
0204060
80100120140
160180
Un
it S
ales
(in
Mill
ion
s)
19
97
19
98
19
99
20
00
20
01
20
02
Source: CAN Newsletter, June 1999
Data Frame
Broadcasts 0 to 8 bytes of data with identifier
Non-Destructive Arbitration• Similar to Ethernet, each node attempts to transmit when the
network is free.• Unlike Ethernet, there is no collision. The “winning” node
continues to transmit its message to completion• This mechanism GUARANTEES that NEITHER information
NOR time is lost !!• The value of the Identifier defines priority during arbitration• No two Identifiers are alike
MessageMessageIdentifierIdentifierS
tart
AckControl DATA (0-8 bytes) CRC
The CAN Message Protocol
©1998, 1999 ODVAAn Overview of
Arbitration Example
0 0 0 1 00000001 xxxx 01EOF
10110110100 0
Node 1 Transmits:
As seen on the wire:
0 0 0 1 00000001 xxxx 01EOF
10110110100 0
Node 2 Transmits:
0 10110111
Node 2 losing arbitrationand stops transmitting!
Node 2 still ACKs message.
01
Arbitration Field
©1998, 1999 ODVAAn Overview of
The Next Generation Networking Paradigm:
Producer/Consumer
©1998, 1999 ODVAAn Overview of
Two Communication Models
Source/Destination (point to point)
synchronized action between nodes is very difficult as data arrives at a different time to each node wastes bandwidth as data must be sent multiple times when only the destination is different
Producer/Consumer (the data is identified)
multiple nodes can consume the same data at the same time from a single producer nodes can be synchronized more efficient bandwidth usage
src dst data crc
identifier data crc
©1998, 1999 ODVAAn Overview of
Source/Destination Example...
One person (“source”) tells each person (“destinations”) in the room, one at a time, the
current time of day (data) People may choose to ignore, but time and
effort is wasted Time will pass as the “source” communicates to
each “destination”, one by one
Delivery time changes with thenumber of people in the room
©1998, 1999 ODVAAn Overview of
Source/Destination Limitations Requires multiple packets to deliver the same
message to multiple devices Data arrives at different times to different
destinations Puts pressure on network bandwidth Results in the use of different networks for
messaging and time-critical I/O
©1998, 1999 ODVAAn Overview of
Producer/Consumer ExampleOne person states (“produces”) the current time of day
(data) once to one or more people (“consumers”) All people hear the data simultaneously Some people may choose to listen to
(“consume”) the data (acknowledgeby nodding, adjust their watch, etc.)
Others may choose to ignore(“not consume”) the data
Highly deterministic(delivery time consistent ifmore people enter or people leave the room)
©1998, 1999 ODVAAn Overview of
Producer/Consumer (example 2)
message #1 position reference from Sensor multicast to Controller 1, Controller 2, and
HMI
message #2 speed command from Controller 1 is multicast to all Drives 1, 2, & 3, and HMI
multicast less efficient with source/destination peer to peer requires 7 messages vs. 2
Drive1Sensor
Drive3Drive2
#1#2
Controller 1Controller 2
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HMI
©1998, 1999 ODVAAn Overview of
Producer/Consumer Networks can support many communication relationships Polling Cyclic Change-of-State (COS) Combinations Master/Slave, Multimaster, Peer-to-Peer One-to-One, Multicast, or Broadcast
©1998, 1999 ODVAAn Overview of
Producer/Consumer - Benefits Simplifies programming
No controller data management required for non-control functions (e.g., Operator Interface during fault diagnosis)
Improves throughput Network not filled with old data (e.g., sensor status)
Provides more timely responses Data communicated only as needed, one time (e.g., error conditions)
No additional cables required Control AND programming AND diagnostics over the same network
Improves Productivity Engineering, Installing, Maintaining, etc.
©1998, 1999 ODVAAn Overview of
Which Networks Support Which Model? (Examples)
Source/Destination - “the old paradigm” - Ethernet - Profibus (DP, PA, FMS, ...)
- Interbus S - Seriplex
- Modbus - Modbus Plus
- Remote I/O - Data Highway Plus
Producer/Consumer - “the new paradigm” Foundation Fieldbus ControlNet DeviceNet EtherNet/IP
©1998, 1999 ODVAAn Overview of
Others using Producer/Consumer Sun Microsystems - Java API’s (“InfoBus”) use
Producer/Consumer allowing interoperable applets on a Web page to communicate with each other Source: NetworkWorld, 20-Oct-97
Microsoft - “… threads have a producer-consumer relationship (actively cooperating on a common goal) rather than a mutual exclusion relationship (trying to avoid conflicts while sharing a common resource).”Source: www.microsoft.com, 27-Oct-97
©1998, 1999 ODVAAn Overview of
EtherNet/IP
Extends commercial off-the-shelf Ethernet with an open, industrial protocol for automation purposes
Based on encapsulated ControlNet and DeviceNet messages inside TCP/UDP/IP protocol
Provides explicit (request/response) and implicit (real-time I/O data) messaging
Configuration of multiple DeviceNet networks from a single PC on Ethernet
Simple routing between DeviceNet and Ethernet Supported by ControlNet International, Industrial
Ethernet Association and ODVA Visit the EtherNet/IP section of the ODVA Web site
(www.odva.org) for additional information
©1998, 1999 ODVAAn Overview of
Multi-Vendor Interoperability using Published Device Profiles
Vendor A Vendor B Vendor C
start/stop start/stop start/stop
fwd/rev fwd/rev fwd/rev
accel/decel accel/decel accel/decel
power calc. power calc. power calc.
Vendor A Vendor B Vendor C
other eng. units foreign lang. (none)
temp. calc.
AC Drive Profile (example)
Vendor Value-Add
Published in Spec.
About
©1998, 1999 ODVAAn Overview of
Open DeviceNet Vendor Association Mission Manage DeviceNet Technology
Publish Specifications Publish Test Software, Run Test Centers Provide a forum for directing the future of DeviceNet
technology and products
Provide DeviceNet Tools and Services for Users and Systems Integrators
Pursue International Standardization Reduce Vendor Time-to-Market Promote DeviceNet
Manage common marketing efforts of group members
©1998, 1999 ODVAAn Overview of
All ODVA Members manage DeviceNet technology
Any vendor can join ODVA and participate in the Special Interest Groups (SIGs)
SIGs contribute enhancements to the DeviceNet Specifications
Big companies and small companies have equal say
ODVA bylaws protect non-obsolescence
©1998, 1999 ODVAAn Overview of
ODVA has a global presence
ODVA
Test LabU of Michigan
Test LabU of Warwick
ODVAJapan
ODVA NewZealand
ODVAAustralia
ODVAChina
ODVAKorea
ODVA Europe
Test LabASTEMJapan
DeviceNetUK
Special LabTexas A&M
©1998, 1999 ODVAAn Overview of
Five Years of Membership Growth
74
112
136163
207
243274
293 307
323
0
50
100
150
200
250
300
350Q
3'95
Q1'
96
Q3'
96
Q1'
97
Q3'
97
Q1'
98
Q3'
98
Q1'
99
Q3'
99
Q1'
00
©1998, 1999 ODVAAn Overview of
Membership
Over 300 member companies worldwide– ABB, Allen-Bradley, ASCO/Joucomatic, Banner,
Beldon, Cutler-Hammer, Festo, Fischer-Rosemount, Hitachi, Mitsubishi, Nematron, Omron, Parker Hannifin, Pepperl+Fuchs, Reliance, Schneider Electric, SMC, SST,Toshiba, Turck, Wonderware, etc.
Over 100 SI/OEM members– Alvey, Jervis B. Webb, KR Automation, Rapistan
Demag, ...
©1998, 1999 ODVAAn Overview of
Association Services
Maintain Vendor ID Registry Operate Independent Test Labs Provide Training for Developers and Implementers Information Source (Literature Fulfillment, Telephone
Referrals to Experts) Resolve multi-vendor product malfunctions and
adjudicate non-conformance issues Web Site: www.odva.org Dr. DeviceNet (free technical support)
©1998, 1999 ODVAAn Overview of
ODVA Tools DeviceNet Network Monitor Detect shorts Monitor voltage levels;
indicate high or low voltage conditions
Auto-detect bus speeds; indicate 125,250 0r 500 kbps
Monitor bus traffic and identify Group 1, 2, 3 and 4 traffic
Detect and indicate error frames
©1998, 1999 ODVAAn Overview of
System design tool does power and distance limit checks Selects cable components; auto-generates bill-of-material
ODVA Tools DeviceNet Assistant
©1998, 1999 ODVAAn Overview of
New ODVA Training Services
DeviceNet University 2-day hands-on multi-vendor user training held at
various locations throughout North America Teaches students the correct way to install and
troubleshoot DeviceNet For locations and dates, visit the ODVA Web site
(www.odva.org)
©1998, 1999 ODVAAn Overview of
ODVA Publications
• Product Catalog (Print, CD ROM and Web)• Specifications (Print and CD ROM)• Newsclips• DeviceNet News Newsletter
©1998, 1999 ODVAAn Overview of
Introducing the Redesigned Web Site
©1998, 1999 ODVAAn Overview of
www.odva.org
DeviceNet Product Catalog Technical Overview Downloadable Technical Presentations and
Papers Links to Related Sites (Members, Bus
Technical Information) E-mail links to experts Member information, contacts
©1998, 1999 ODVAAn Overview of
Dr. DeviceNet Free technical service
Design Installation Application Troubleshooting
Available to anyone ODVA has 12 volunteer DeviceNet experts around
the world to provide support e-mail to [email protected] or go to web
site www.odva.org Reply from DeviceNet expert in 24-48 hours
©1998, 1999 ODVAAn Overview of
Five Years of New, Innovative Products
52
128
166
283
350
367
0
50
100
150
200
250
300
350
400M
ar-
95
May-9
6
Jan
-97
May-9
8
Jan
-99
Mar-
00
©1998, 1999 ODVAAn Overview of
Products AvailableSensors
Valves
Motor Protection/Control
AC/DC drives
I/O
PLCs
PC Interfaces
S/W products
HMI
Developers’ Tools
many others
©1998, 1999 ODVAAn Overview of
Certification MarkCertification Mark
©1998, 1999 ODVAAn Overview of
Certification MarkCertification Mark
©1998, 1999 ODVAAn Overview of
Gary Workman Quote on Conformance Testing
"Open systems create a competitive marketplace which is advantageous to the end user. However, if products aren't interoperable and interchangeable, it's a moot point," said Gary Workman of GM, explaining the rationale behind the new policy that GM North American Operations will only purchase conformance tested products.
©1998, 1999 ODVAAn Overview of
Five Years of Escalating Node Counts(and several years of node count limbo)
Nu
mb
er o
f In
stal
led
No
des
-
150,000
300,000
450,000
600,000
750,000
Q3'95 Q1'96 Q1'97 Q1'98 Q1'99 Q1'00
???
©1998, 1999 ODVAAn Overview of
Market Report
By the year 2001, 47% of end users indicate they will purchase DeviceNet (up from 39% today).
– Source: Control Engineering survey, March 1999
A majority of end users and OEMs surveyed have chosen DeviceNet over other networks.
– Source: Venture Development Corporation research study, 1998
Worldwide revenue in the industrial networking market will reach $2.8 billion by the year 2003 (up from $1.9 billion in 1998).
– Source: Industrial Controls Intelligence & the PLC, April 1999
Twenty-four percent of all devices (29 million) will interface with industrial networks by 2002.
– Source: Control Magazine, June/July 1999
©1998, 1999 ODVAAn Overview of
Industries & Applications
Automotive Food & Beverage Material Handling Packaging High-speed Assembly Pulp & Paper Semiconductor Fabrication
©1998, 1999 ODVAAn Overview of
Key Customers
John Deere LaFarge Cement Motorola Nestle Pepsi Proctor & Gamble Philip Morris Quaker Oats Ralston-Purina
Anheuser-Busch Applied Materials Baxter Healthcare Caterpillar DuPont General Motors Giddings & Lewis Heineken Hershey Foods
©1998, 1999 ODVAAn Overview of
Best Opportunities for DeviceNet
“Greenfield” w/designed-in features Retrofits where time-out-of-service is
valuable; any project where time is critical Acceptance Test on system house floor
required or beneficial Field changes are anticipated Device diagnostics are needed for
increased system uptime Post-installation service call is costly
©1998, 1999 ODVAAn Overview of
http://www.odva.orge-mail: [email protected]
(954) 340-5412
(954) 340-5413 fax
for more information, contact:
©1998, 1999 ODVAAn Overview of
Frequently Asked Questions
©1998, 1999 ODVAAn Overview of
Is DeviceNet maximum distance long enough?
DeviceNet’s maximum distance is 500 m (1,640 ft). Is that long enough?
Typical device level installations are smaller than an average automobile. Yes, 500 m is long enough. For the non typical installations, fiber optic repeaters are available to extend the distance up to 4 km.
©1998, 1999 ODVAAn Overview of
How does DeviceNet integrate with existing control systems?
DeviceNet can be integrated with many existing control systems using the existing PLC based controllers or off the shelf gateway solutions. In fact, the top 6 global PLC vendors support the integration of DeviceNet with their PLCs. Additionally, off the shelf gateway products are available to integrate DeviceNet with many proprietary plant protocols.
©1998, 1999 ODVAAn Overview of
Is DeviceNet fast enough?
DeviceNet’s fastest speed is 500 Kbaud. Is that fast enough?
Maximum throughput should be a measure of 3 factors: Network Model, Protocol Efficiency, and baud rate.
Network Model has the greatest impact on maximum throughput as it defines how information is distributed across the network. Examples of network models include the source / destination model and the modern producer / consumer model. Examples of producer / consumer models used today include DeviceNet, ControlNet, Fieldbus Foundation, Sun Microsystems Infobus, and Microsoft software (threading).
Protocol efficiency is the measure of network overhead when sending data on the wire. Standard polling (scanning) of all connected nodes has a fixed efficiency and is usually not flexible. DeviceNet allows the use of standard polling but also allows Change of State (COS) and cyclic (timed interval) which can dramatically reduce network traffic, thereby lowering the I/O scan time and improving the network efficiently.
The last measure of throughput is Baud Rate. Baud Rate defines how quickly data travels on the network from one point to another point.
With DeviceNet’s producer / consumer model and efficient protocol options, DeviceNet works smarter rather than working harder. With the combination of the producer / consumer model and efficient protocol options, DeviceNet’s 500 kbaud is fast enough for device level applications.
©1998, 1999 ODVAAn Overview of
Definition of Determinism
Determinism:1. The ability to calculate with certainty, within a defined limit or
range of time, when data is sampled, produced, delivered or made available to other networked nodes.
2. The ability to maintain a stable data production rate regardless of other variations of traffic (e.g. addition of nodes, increase in data size) on a network.
3. Ability to calculate with confidence the worst-case schedule for when data will be accessible to other devices in a system.
Increases in traffic typically result in a reduction of network determinism.
©1998, 1999 ODVAAn Overview of
DeviceNet Determinism
DeviceNet can be very deterministic when certain criteria is met with the network configuration. In order to maintain a high degree of determinism, it is necessary to control the production of data on a network while minimizing any collisions of data production from other nodes.
Criteria for maximizing DeviceNet determinism: Polled System (High Determinism):
Single-master network configured as Master-Slave/Polled system. Master controls all data requests and data production to/from all slave devices. Network node count and message length from each node fixed. Variables (e.g. adding of nodes, adjustments to message length) are minimized.
Variable introduced will impact range of determinism in the system. Cyclic System (Limited Determinism):
Network is configured using only cyclic devices. Network node count and message length from each node fixed in size. Data collisions are minimized via a fixed data production schedule for nodes. Variables (e.g. adding of nodes, adjustments to message length) are minimized.
Variable introduced will impact range of determinism in the system.