Buses and Networks
Bela G. Liptak · 2002
The Company Network Today 435 Enterprise and Plant Management Level 435 Control Level 435 I/O Level and Field Level 438 The Way Ahead 440 Ethernet 440 Wireless 440 Interchange Formats 440 Device Operation Standards 441 Conclusion 441 References 441 4.2 PLC PROPRIETARY AND OPEN NETWORKS 442 The General Philosophy of Communication 442 Architectures 444 Building Blocks 444 Physical Media Access and Arbitration Methods 445 Logical Media Access and Arbitration Methods 445 Physical Layer-Overall Theory of Operation 446 Types of Cable and Other Media 446 Optical Fiber Cable 448 General Installation Guidelines 449 Types of Connectors 449 Transmission Techniques 449 Numbering Systems and Conversion Formulae 452 Open Protocols 453 Industry Open Standards 453 RS-232C 453 RS-422 455 RS-485 455 Ethernet 456 MODBUS 461 Proprietary Protocols 461 MODBUS Plus 461 Data Highway Plus 462 Other Control Networks 462 General Troubleshooting 462 Preventing Problems 462 Diagnosing Problems 462 References 463 Bibliography 464 Web Sites for Reference 464 4.3 HARDWARE SELECTION FOR FIELDBUS SYSTEMS 465 Fieldbus Devices 465 Similarities to Conventional Devices 465 Differences from Conventional Devices 465 Future Capabilities 466 Function Blocks 467 Resource Blocks 468 Transducer Blocks 468 Converting an Existing Installation 469 Cable 470 Network Layout 471 Point-to-Point or One-to-One Topology 471 Spur Topology 471 Tree or Chickenfoot Topology 472 Daisy Chain 472 Power Supply 472 Location on Segment 473 Segment Design Rules 473 Power 473 Bandwidth 474 VCRs 474 Terminations 475 Prewired Blocks 475 Terminals 476 “Short-Circuit” Protection 476 Barriers 476 Terminators 476 IS/NIS/FISCO 476 Repeaters 477 Reference 477 4.4 SORTING OUT THE PROTOCOLS 478 The Perfect Network 478 Protocol Layering 478 OSI Model 478 TCP/IP Model 479 Communication Basics 480 Data Transmission 480 Asynchronous Communications and Serial Ports 480 Parity 481 Manchester Encoding and Synchronous Communications 481 Cyclic Redundancy Codes 481 Analog Signaling 481 Framing Messages 482 Sharing the Communication Channel 482 Network Soup 482 Sensor Level 483 AS-i 485 CAN 485 DeviceNet 486 Interbus 486 LON 486 Device Networks 487 Foundation Fieldbus H1 487 HART 487 PROFIBUS-PA 489 Control Networks 489 BACnet 489 ControlNet 491 Industrial Ethernet 491 Ethernet/IP 491 FF-HSE 492 MODBUS 492 PROFIBUS-DP 492 Enterprise Networking 493 LANs 493 Protocols 493 The Internet 493 Choosing the Right Network 494 References 494 4.5 OVERALL FIELDBUS TRENDS 495 Factory Communication Systems 495 Use of Fieldbuses In Industrial Plants 495 Fieldbus Functions 496 Cyclic Data Exchange 496 Asynchronous Traffic 497 Messaging System 498 International Standards And Proprietary Products 498 European Standards 498 International Standards 498 Proprietary Fieldbuses 499 Performance 499 Redundancy and Failure Considerations 499 Physical Medium Failures 500 Station Failures 501 Transmission Errors 501 Market Situation and Trends 501 Use of Ethernet Networks 502 References 503 4.6 FIELDBUS ADVANTAGES AND DISADVANTAGES 505 Advantages 505 Bidirectionality 506 Condition-Based Maintenance 506 Disadvantages 506 “Mixed” Signals 507 Architecture 507 Maintenance Tools 507 Interconnectivity 508 Ethernet Connectivity 508 Connecting to the Corporation 508 Economics 508 Initial Capital 509 Commissioning 510 Life Cycle 510 References 512 4.7 FIELDBUS DESIGN, INSTALLATION, ECONOMICS, AND DOCUMENTATION 513 Process Automation Buses 513 Bus Basics 513 Teams 513 Fieldbus Resources 513 Design 513 Strategies 513 Integration 514 Application Software 515 Installation 515 Strategies 515 Training 515 Commissioning 516 Segment Testing 516 Field Device Testing 516 Operational Testing 516 Documentation 516 Strategies 516 P&ID Representation 516 Segment List 516 Segment Drawings 517 Specifications 517 Host Specifications 517 Field Device Specifications 517 Procedures 519 Maintenance 519 Economics 519 Strategies 519 Design 519 Documentation 519 Installation and Commissioning 519 Maintenance 520 Cultural Aspects 520 New Technology 520 Integration 520 Training 520 Teamwork 520 Conclusions 520 References 521 Bibliography 521 4.8 INSTRUMENTATION NETWORK DESIGN AND UPGRADE 522 Measured and Key Variables 522 Instrumentation Design Goals 523 Cost-Optimal and Accurate Sensor Networks 523 Example 524 Design for Maximum Precision 524 Parameter Estimation 525 Precision Upgrade 525 Example 526 Resource Reallocation 527 Example 527 Reliable Sensor Networks 528 Repairable Sensor Networks 528 Example 529 Robust Sensor Networks 529 Example 530 Design of Sensor Networks for Process Fault Diagnosis 530 Design of Sensor Networks for Process Fault Resolution 531 Conclusions 531 Nomenclature 532 References 532 4.9 GLOBAL SYSTEM ARCHITECTURES 534 Purpose of Each Network 534 WANs and LANs 534 Control-Level Network 535 Field Network 535 Network Segmentation 535 Eliminate Unnecessary Traffic 536 Achieve Deterministic Behavior 536 Network Security and Privacy 537 The Function of Firewalls 537 Functions Required for Automation Systems 537 Automation Gateways 537 Network Technology 537 Cabled Networks 537 Optical Free-Air Networks 537 Wireless Networks 538 4.10 ADVANTAGES AND LIMITATIONS OF OPEN NETWORKS 540 ISO/IEC 7498 Open System Interconnection (OSI) 540 Seven-Layer Standard 541 Functions of the Layers 541 Application 541 Presentation 541 Session 541 Transport 541 Network 542 Data Link 542 Physical 542 Missing Layers 542 TCP/IP Network of the Internet 542 Common Network Protocols Included in TCP/IP 542 Open Application Layers and Industrial Networks 543 DeviceNet, ControlNet, and Ethernet/IP 543 MODBUS and MODBUS/TCP 544 Foundation Fieldbus and Foundation Fieldbus/HSE 545 PROFIBUS and PROFInet 546 Future of Industrial Networks 546 4.11 HART NETWORKS 547 Evolution of the “Smart” Field Device 547 Evolution of the HART Protocol 548 The HART Communication Foundation 548 Early Adopters of HART 549 Climbing the Automation Pyramid 549 HART Field Devices 550 Backward Compatibility 553 Calibrating HART Field Devices 554 Calibrating the Process Variable 554 Scaling the Process Variable 554 Producing the Loop Current 555 Host Applications 555 Host Conformance Classes 555 Understanding I/O System Trade-Offs 556 Multidrop Connections 556 Multichannel I/O Systems 556 Impacts of Burst Mode on I/O Performance 557 Installing HART Networks 557 Understanding the HART Physical Layers 557 HART Network Guidelines 558 Device Descriptions 559 Applications 560 Using HART in Control Systems 560 Maximizing the Value of HART Current Loop Support 560 SCADA Applications 561 Control in the Field 561 Instrument Management 562 Valve Diagnostics 562 OPC 563 Conclusion 563 References 563 Bibliography 563 4.12 FOUNDATION FIELDBUS NETWORK 564 History 564 Based on ISA/ANSI S50.02 and IEC 61158 Standards 565 Fieldbus Architecture 565 Physical Layer 567 Data Link Layer 569 Link Active Scheduler 569 Publish/Subscribe Data Distribution 569 Application Layer 570 Mapping to Data Link Layer for H1 570 Mapping to TCP/IP and UDP/IP over Ethernet for HSE 570 User Layer 571 Field Control 571 Function Block Diagram Programming 572 Function Block Library 572 Analog Input 573 Analog Output 573 Bias 574 Control Selector 574 Discrete Input 574 Ratio 574 Discrete Output 574 Manual Loader 574 Proportional/Derivative (PD) 574 Proportional/Integral/Derivative 575 Output Signal Selector 575 Splitter 575 Dead Time DT 575 Lead Lag 575 Complex Analog Output 575 Device Control 575 Analog Alarm 575 Discrete Alarm 575 Arithmetic 575 Pulse Input 575 Complex Digital Output 575 Calculation Block 575 Analog Human Interface 575 Discrete Human Interface 575 Set Point Generator 575 Integrator 576 Characterizer 576 Step Control 576 Cascade Control Concepts 576 References 577 4.13 PROFIBUS-PA 578 PROFIBUS-DP Basics 578 PROFIBUS-PA Basics 578 System Architecture 579 Bus Access Method 581 PROFIBUS-PA Block Model 582 Device Management 583 Physical Block 583 Transducer Blocks 583 Function Blocks 583 Applications in Hazardous Areas 583 Network Design 584 Telegram Length 584 Cycle Times 584 System Configuration 586 Future Developments 587 Conclusion 587 Reference 587 4.14 DESIGNING PROFIBUS-PA AND FOUNDATION FIELDBUS SEGMENTS 588 General Considerations 588 Cable Length 588 Fieldbus Devices 589 Power Supply 589 Network Design 590 Fieldbus Segment for a Nonhazardous Area 590 Foundation Fieldbus (IEC 61158-2) Segment to Ex i 592 FISCO EEx ia IIC Segment 594 Other Possibilities 596 Grounding Schemes 596 Single-Point Grounding 597 Multipoint Grounding 598 Multipoint Grounding with Capacitive Isolation 600 Troubleshooting 600 Bibilography 600 4.15 ETHERNET AND TCP/IP-BASED SYSTEMS 601 The Core Elements of Ethernet 601 Understanding CSMA/CD 602 Ethernet Frame Format 602 Topology Overview 603 Ethernet Hardware 604 Network Interface Card 604 Transceivers 604 Repeaters and Hubs 604 Bridges 604 Routers 604 Gateways 605 Switches 605 Choosing the Right Hardware 605 Overview of the Ethernet Versions 605 10 Mbps Ethernet Standards 606 Fast Ethernet Standards 606 Gigabit Ethernet 607 Future Standards 607 TCP/IP Overview 607 What Is TCP/IP? 607 Basics of TCP/IP Addressing 608 IP Routing Basics 608 Should Ethernet and TCP/IP be Used on the Plant Floor? 609 Tough Enough for the Plant Floor? 609 Ethernet Cabling 609 Ethernet Connectors 610 Power over Ethernet Cabling 610 Interface Performance Issues 610 Application Layer Protocols 611 Conclusions 611 References 611 Bibliography 611 4.16 FIELDBUS NETWORKS CATERING TO SPECIFIC NICHES OF INDUSTRY 612 DeviceNet 612 DeviceNet Physical Layer 612 DeviceNet Data Link Layer 612 DeviceNet Application Layer 613 ControlNet 614 ControlNet Physical Layer 614 ControlNet Data Link Layer 615 ControlNet Network and Transport Layers 616 ControlNet Presentation Layer 616 ControlNet Application Layer 616 Lonworks 617 Lonworks Physical Layer 617 Lonworks Data Link Layer 618 Lonworks Network Layer 618 Lonworks Transport Layer 618 Lonworks Application Layer 618 WorldFIP 619 WorldFIP Physical Layer 620 WorldFIP Data Link Layer 620 WorldFIP Application Layer 621 Actuator Sensor Interface 621 AS-i Physical Layer 621 AS-i Data Link Layer 621 AS-i Execution Control 622 PROFIBUS-DP 623 PROFIBUS-DP Physical Layer 623 PROFIBUS-DP Data Link Layer 624 User Interface and Direct Data Link Mapper 624 PROFIBUS-DP Extended Functions 625 References 625 4.17 PROPRIETARY NETWORKS 627 Primary Uses of a Proprietary Bus 627 Disadvantages of a Proprietary Bus 627 Modbus Networks 628 Communication Transactions 628 Transmission Modes 629 ASCII Mode 629 RTU Mode 629 MODBUS Message Framing 629 ASCII Framing 629 RTU Framing 629 Field Descriptions 629 Address Field 629 Function Code 630 Data 630 Error Checking 630 Data Highway 630 Physical Implementation 631 Software Layers 631 Application Layer 631 Command Structures 632 Message Format 632 Field Descriptions 632 Asynchronous Link Protocols 633 Full-Duplex Transmission 633 Half-Duplex Transmission 634 Genius Bus 634 Overview 634 Physical Implementation 635 I/O Service 635 Datagrams 635 Global Data 637 Bibliography 637 4.18 FIBER-OPTIC NETWORKS 638 Principles of Fiber-Optic Networks 638 Why Use Fiber Optics? 638 How Fiber Optics Works 638 Components 639 Types of Fiber-Optic Cables 639 Fiber-Optic Core/Cladding Dimensions 640 Single Mode vs. Multimode 640 Cable Construction 640 Loose Tube Cables 641 Tight-Buffered Cables 641 Cable Protection 641 Fiber Count 642 Fiber-Optic Network Design 642 Distribution and Layout Planning 642 Cable Selection 643 Indoor Office Installations 643 Indoor Industrial Installations 643 Interbuilding Installations 643 Long-Run Outdoor Installations 643 Power Loss Budgeting 643 Cabinets and Cable Management 644 Fiber Cable Installation and Finishing 644 Fiber Installation Concepts 644 Pull Strength 644 Bend Radius 644 Crush and Impact Strength 644 Terminating the Fiber 645 An Overview of Splices 645 An Overview of Connectors 645 Cable Management and Labeling 646 Inspection and Testing 646 Inspecting Connectors with a Microscope 646 Attenuation Testing 647 Optical Time Domain Reflectometers 647 Conclusions 647 References 648 Bibliography 648 Acknowledgments 648 4.19 SATELLITE, INFRARED, RADIO, AND WIRELESS LAN NETWORKS 649 Radio Systems 650 IEEE 802.11 (CSMA/CA) 650 CSMA/CA 650 Bluetooth (IEEE 802.15/Wireless Personal Area Networks/WPAN) 651 General Physical Characteristics 651 Time Slots 652 Physical Links 652 Packets 652 Access Code Field 652 Access Code Types 653 Packet Header 653 Channel Control 653 Operating Procedures and States 654 The Connection State 654 Scatternets 655 Cellular Telephony 655 Channels and Clusters 656 Call Switching 657 Call Processing 657 Multiplexing 658 FDMA 658 TDMA 658 CDMA 659 Spread Spectrum 659 Direct Sequence Spread Spectrum 659 Frequency Hopped Spread Spectrum 659 Wireless Data 659 SMR 659 CDPD 659 PCS 661 Satellite LANs 661 Basic Satellite Technology 661 Satellite Orbits 662 Low Earth Orbit Satellites 662 Little LEOS and Big LEOS 662 Medium Earth Orbit Satellites 662 Geosynchronous Earth Orbit Satellites 662 Communication Bands 662 L Band 663 C Band 663 Ku Band 663 Ka Band 663 Satellite Networks 663 Routing 663 Signal Handoff 663 Protocols 663 Infrared Systems 663 Infrared LANs 664 Infrared Serial Link Access Protocol 664 Physical Layer Characteristics 664 Data Encoding 664 Configurations and Operating Characteristics 665 Frame Format 665 Address Field 666 Control Field 666 Poll/Final (P/F) Bit 666 Operating Procedures for an Infrared Link 666 Procedure Descriptions 666 Very Fast Infrared 668 Bibliography 668 When this section first appeared in the IEH in 1995, the 486 chip had just appeared on the market and personal computers ran at around 60 MHz. Today, we are three chip generations further on and PC speed has increased 200-fold and more. It is predicted that this trend will continue throughout the decade, until the physical limits of the present technology are reached.