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Copyright 2010 ISA. All Rights Reserved.

Ethernet I/O

Brad S. Carlberg
Jim McConahay
Standards
Certification
Education & Training
Publishing
Conferences & Exhibits

Distributed with permission of author(s) by ISA 2010 Presented at ISA Automation Week 2010; http://www.isa.org


Co-Presenter: Brad S. Carlberg

Brad S. Carlberg, P.E. is a Consulting Engineer in Richland,
Washington. He is a Registered Professional Control Systems
Engineer in the states of Alabama and Washington with over twenty-
five years experience in industrial automation and Process Control
Engineering. Specifically he has experience with Distributed Control
Systems and Programmable Logic Controllers combining extensive
experience with both Hardware and Software Design, Programming,
Implementation and Startup. Brad received his Bachelor of Science
in Mechanical Engineering from Washington State University in
Pullman, Washington in 1984. Brad is a Senior Member of ISA who
has been a conference program committee member since 1997.

BSC
Engineering

2


Co-Presenter: Jim McConahay

Jim McConahay, P.E. is an ISA member and holds a BSEE and
MBA from Cal Poly University, Pomona California. Has 30+ years
design and installation experience in Production and Automation
equipment. Jim is a Sr. Field Application Engineer for Moore
Industries-International, Inc. concentrating on process control
instruments, SCADA, SIS (Safety Instrumented Systems), fieldbus,
data concentrators and communications links.

3


Agenda

Agenda
Physical Layers of Ethernet

Protocol Medley

Migration From Cabinet to the Plant Floor

Enhanced Features of Ethernet I/O

Architecture Considerations

Security

Examples of Ethernet Communications

4


OSI Model

OSI (Open Systems Interconnect) Model

7
Application
6 Presentation “Ethernet” IEEE 802.3x only applies here

5 Session

4 Transport

3 Network

2 Data Link
Physical UTP, STP, Fiber, Coax, etc.
1 10/100/1000/10G speeds

5


OSI Model

Protocols run on top of Ethernet

7 MODBUS, OPC,
What “language” are you talking??
HTTP, Etc. Protocol
6 Presentation
5 Session
Addressing and Handshaking Protocols
4 TCP

3 IP

2 Ethernet UTP, STP, Fiber, Coax, etc.
Ethernet
1
6


Open Standards

Ensure that your Ethernet I/O supports open
standards for connectivity: OPC, MODBUS/TCP,
Ethernet/IP, HTTP, HSE etc.

OPC

HTTP

MODBUS/TCP
Ethernet/IP HMI, PC,
FF HSE DCS, PLC
CIP

7


Communications Media

Ethernet vs. Twisted Pair

Speed
Multiple Protocols over same cable
Plant wiring infrastructure
Non-Proprietary hardware available (lower cost)
Switch advancements have improved determinism
Power over Ethernet

HMI, PC,
DCS, PLC
8


Protocol Gateway

What if the protocols don’t match?
Is there a solution?

Gateway
(Protocol Converter) HMI, PC,
Ethernet to Ethernet DCS,PLC
Ethernet to Serial
Wireless to Serial/Ethernet

9


Protocol Gateway

Protocol Converters and Gateways
• The term “gateway” has many meanings. One common definition is a
protocol converter.

• Sometimes host and legacy systems can only communicate via one
particular protocol. Or, instruments may support one protocol but not the
one that the host system supports. Gateways can be very effective
solutions that connect these two devices. Since Ethernet is “open”
gateways are becoming more and more common.

• Sometimes people refer to “drivers” as gateways. A driver is essentially a
protocol or language translator.

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Simplified Gateway Example

Gateway
HART Data Map MODBUS Data Map
Gateway
Internal Mem.

MODBUS
HART mapping
Slave
Master
68.6 68.6

MODBUS Master
gets new data

HART Device is polled MODBUS Data Map

Internal Mapping Takes Place
11


Moving from the Cabinet to the Field

• Temperature Considerations 55C vs. 85C operating Temp’s.

• Channel-to-channel, and input-to-output signal isolation
eliminates unpredictable ground loops

• RFI/EMI protection protects against plant noise

• Accuracy, long term stability, and Input/output resolution of
transmitters

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Isolated Channels

Signal Inputs/Outputs

A/D Converter Typical I/O Card Design
mP -single point of failure
-isolation
Common I/O Multiplexer

Signal Signal Signal Signal
Input Input Input Input

Transmitter Like Design
A/D A/D A/D A/D
-isolation
-flexibility of input type
mP mP mP mP
Enhanced I/O Design

13


Isolated Channels

Power and Flexibility of
PLC’s Resolution, Accuracy,
(Cabinet Mounted) and Spec’s of Field
Transmitters
(Field Mounted)

Plant Floor “Industrialized” Ethernet I/O
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“Hardened” Plant Floor Switches

•High Temp -40 to 85C vs. commercial ~45C
•High Vibration Tolerance
•RFI/EMI Rejection
•Surge Protection
•Dual Power Supply Options for UPS Systems

15


Switch Features for the Plant Floor

•QoS (Quality of Service) -Packet Prioritization
•SNMP (Simple Network Management Protocol)
•SMTP Client (Emails about network warnings/breaks)
•MAC Layer Filtering
•IP Layer Filtering

16


Set-Ups

Programming should be easy and
intuitive; i.e. web based

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More…

Do you need more than I/O gathering?
Ethernet I/O systems are smarter and more powerful than ever.
Many times PLC’s are used to perform simple control, math and
logic functions.

Questions to ask your Ethernet I/O vendor
1. Does your Ethernet I/O have the ability
to perform control and math?
2. Is the control programming language
proprietary?
3. …

18


Compliant Language

Is the programming language
61131-3 compliant?

Function Block Diagram (FBD) Example
19


Topology

Know your design needs before
choosing your Ethernet I/O system

1. Peer-to-Host—Star Topology; Bus Topology

2. Peer-to-Peer

3. Hybrid—Peer-to-peer and Peer-to-Host

4. Wireless/Fiber/Copper

20


Peer-to-Host System
DCS, PLC or PC
with HMI/SCADA
(with NET
Concentrator
System OPC
Server)

Ethernet I/O
System Ethernet I/O
System

Additional NET
Concentrator System
Stations or Uplink to
Other Hubs or
Ethernet I/O Ethernet Switch or Hub Switches Ethernet I/O
System System

Dispersed Monitoring & Control Devices
Analog Direct Valve On/Off
Transmitter Temperature Positioners Devices
Sensors
Temperature
Pressure RTD On/Off Contact Closure
Level Thermocouple Proportional Relay

21


Peer-to-Peer System

(cost savings with traditional I/O cards)

Ethernet/Fiber Network
PAIR 1 Ethernet I/O System Ethernet I/O System

Ethernet I/O Ethernet I/O
PAIR 2 System System

Ethernet I/O System Ethernet I/O System
PAIR 3

22


Add Wireless…

Wireless Peer-to-Peer/Host Systems
900Mhz or 2.4Ghz – License Free or Licensed



23


Security Concerns

Firewalls

NAT Routers

Virus Protection

Physical Security (personnel and Internet Connection)

“Line speed” packet encryption systems

24


Networking

Network Architecture Considerations- “Connected”

VPN

Outside Internet
Front Office Network
Connections
Typical

Most Convenient
Router/Firewall
but Potentially
Vulnerable

Process Control Network

25


Networking

Network Architecture Considerations- “Disconnected”

VPN

Front Office Network Outside Internet
Connections
Typical
Safer but
Inconvenient No Physical Connection

Process Control Network

26


Case Study #1
One communication loop, multiple bus

Problem:
• PAC – Programmable Automation Controller
• Ethernet card in PAC backplane – Ethernet TCP/IP
• HMI
• Ethernet IP and Ethernet TCP/IP
• Flow, valves, level sensors / FF
• FF FIM; H1 to HSE link – Ethernet IP (not TCP/IP)
• Ethernet protocol conflict between FIM and PAC

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Case Study #1
One communication loop, two bus
Solution:
• Add MODBUS TCP to Ethernet IP Protocol Converter
– Two way FF protocol conversion with PAC
Protocol
Converter
Converts
Modbus TCP
to Ethernet IP
Foundation
Fieldbus Managed
FT Interface Ethernet
Module Switch
PT FOUNDATION Fieldbus H1 Modbus TCP Local
FIM HMI
LT Ethernet IP Display

FOUNDATION Fieldbus Ethernet IP
FT
Transmitters

PT

LT
Programmable
Automation
Controller
(PAC)

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Case Study #1
One communication loop, two bus

• Optimized equipment for each part of the system

• Used protocol converter to make compatible
– Lowest cost item in the system
– Far less cost than compromise performance of a single vendor
solution

29


Case Study #2
Remote ESD for Oil Platform in Gulf

Problem:
• Maintenance Boat and Oil Rig Platform pipeline repairs
• Repairs involve heavy equipment above seafloor pipelines
• If accident event, need system to shut down Production
• ESD (Emergency Shutdown Device)
• Automatic
• Reliable
• Two-way verification of link
• Off shore
• Portable, distance >100 km
• Beyond radio links

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Case Study #2

Considerations:
• No hard line communication links
• No ESD = No Drilling ($$$)
• Is existing Emails, Internet and VoIP to shore facilities
– Satellite link is reliable on platform
– Satellite link is reliable on Maintenance ship
• Maintenance ship is very mobile
– Easy installation
– Transferrable to new ship
– Simple, intuitive to operate

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Case Study #2

Solution:
• Data concentrator on Maintenance boat
– Ethernet Communications module
– Discrete input/output module
– Packaging with switch plus display lamp tree
• Data concentrator of Oil Platform
– Ethernet Communications module
– Discrete input/output module
– Packaging with switch, klaxon, plus display lamp tree
– Connection to control panel
• Expansion
– Add SCADA to ESD at negligible cost

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Case Study #2

Things at the surface can drop onto sea floor pipelines

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Case Study #2

• Success
– Operational upon initial installation, continuous operation
– Simple to operate, intuitive.
– Reliable. Now hard-wired to control panel circuits.
– Satellite signal limited by extreme weather.
• Expansion
– Can add I/O modules for telemetry on both ends of links;
negligible cost.

34


Case Study #3
Expansion of 4-20mA loops

• Problem:
Expansion, low budget, needs more 4-20mA channels
– Requires more 4-20mA channels now
– No budget to replace existing 4-20mA lengthy cable run
– Will require still more channels later
– Discrete contact requirement arising
• Ethernet cable upgrade
– Available in the future, not now
– Does not want to waste investment in temporary data
concentrator when Ethernet cable becomes available in the
future

35


Case Study #3
Expansion of 4-20 loops

• Solution
• Data Concentrator
– MODBUS RTU communications at module each site
– AIM each output; AOM each output
– DIM each discrete input; ROM each discrete output
– Increase number of I/O modules, as desired
– Increase pairs of data concentrators
• Use existing twisted pair cable
– Use one twisted pair to carry ‘all’ channels between data
concentrators

36


Case Study #3

• Data Concentrator on a Peer-to-Peer network
– Originally MODBUS Communications Link
– Currently Ethernet Communications Link

37


Case Study #3

Success
• Use data concentrators to collect all 4-20mA loops and
convert to digital communications.
– Increased number of analog channels, and also easily adds
discrete channels
– Only one twisted pair required
– Recreate signal at distant site with no degrading of analog signal
(since communication is digital)
• Low cost Ethernet upgrade
– Swap only the MIM for an EIM communications module
– All other modules are same

38


Case Study #4
Wireless HART, MODBUS RTU & TCP/IP

Problem:
• Multiple tasks, need to optimize
– Tank farm, Wireless HART; multiple sensors, cable expenses
– Closed loop room; add sensors, valves plus data concentrator
– Host control room—long distance communication link
• Different communications media and protocol
– Wireless Hart; radio
– Data concentrator; analog/discrete I/O; programming
– MODBUS
• Need protocol converters
– Wireless Hart to MODBUS RTU slave
– MODBUS RTU master; control loop; MODBUS TCP slave

39


Case Study #4
Wireless HART, MODBUS RTU & TCP/IP

40


Summary
“Our View” - Market Trend with Ethernet
1. MODBUS/TCP
- MODBUS packets encapsulated in TCP/IP frames
Reason: Everyone knows MODBUS, open protocol,
and already supported worldwide
2. Ethernet/IP
- “Industrial Protocol”, Rockwell released to ODVA
(Open DeviceNet Vendor Association)
Reason: Open, supports common publisher/subscriber
method of comm., section of protocol already supported
in open DeviceNet. Uses CIP (Common Industrial Protocol)
for real time control.
3. OPC
-OLE for Process Control. Uses Microsoft’s COM/DCOM/
.NET standards for open comm.
Reason: OPC can run over any physical medium and is an
open, free of charge protocol that both hardware vendors
and software vendors have access to. Many supported
development tools. Strong backing by OPC Foundation.

41


Summary

Market Trend with Ethernet Cont’d
4. HSE
- High Speed Ethernet Foundation Fieldbus protocol
over Ethernet.
Reason: Open protocol, and large organized support
base by Foundation Fieldbus vendors and FF org.
5. Profinet
- Profibus Trade Organization’s answer to open
communications. It is NOT Profibus over Ethernet!!!
Reason: Strong backing by PTO. Can use 802.3 layer
but not restricted to this layer. Can run over modems,
WAN’s, VPN’s, as long as it uses TCP/IP addressing.
6. CIP
- Common Industrial Protocol is being promoted by
ODVA (Open Device Vendors Association). Uses a Producer
consumer network philosophy for real time control applications.

42


Questions?

BSC
Engineering

Thank You!

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