PLC MB+ Networking Planning & Installation Guide 4.0

8/4/2019 PLC MB+ Networking Planning & Installation Guide 4.0

1/255

ModiconModbus Plus Network890 USE 100 00 Version 4.0

Planning and Installation Guide

August 2001


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August 2001

Schneider Electric Inc.One High Street

North Andover, MA 01845

Modicon

Modbus Plus NetworkPlanning and Installation Guide

890 USE 100 00 Version 4.0


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Preface iii890 USE 100 00

Preface

The data and illustr ati ons found in thi s book are not binding. We reservethe ri ght t o modify our products in li ne with our policy of conti nuous

product development . The in formation in th is document i s subject tochange wit hout noti ce and should not be constr ued as a commitment by

Schneider Electric Inc.

Schneider Electric Inc. assumes no responsibi li ty for any err orsthat may appear in this document . If you have any suggestions forimpr ovements or amendments or have found err ors in t his publicati on,

please notify us by using the form on t he last page of this publicati on.

No par t of this document may be reproduced in any form or by anymeans, elect ronic or mechanical, including photocopying, wit hout

express wr it ten permission of the Publisher,Schneider Electric Inc.

Caution: All pertinent state, regional, and local safety

regulations must be observed when installing and using thisproduct. For reasons of safety and to assure compliance with

documented system data, repairs to components should be

performed only by the manufacturer.

MODSOFT is a r egistered t rademark of Schneider Electric Inc.

The following are tr ademarks of Schneider Electric Inc.:

Modbus Modbus Plus Quant um Aut omat ion Ser iesModicon 984

DIGITAL andDEC areregisteredtrademarksofDigitalEquipment

Corporation.

IBM and IBM AT are registered t rademarks of Int ernational

Business Machines Corporati on.

Microsoft and MS---DOS are registered tr ademarks of M icrosoftCorporation.

Copyr ight 2001, Schneider Electric Inc.

Pri nted in U.S.A.


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iv Relat ed Publicat ions 890 USE 100 00

Related Publications

Refer to the following publications for further information about the

Modbus Plus network and other Modicon products.

8 40 U SE 1 00 0 0 Mod icon Q u an t u m Au t om a t ion S er ie s

Hardware Reference Guide

8 40 U S E 1 01 0 0 M od icon L ad de r L ogic B lock L ib r a r y U s er

Guide

8 40 U S E 1 04 0 0 M od icon M od bu s P l u s N e t wor k I /O S er v icin g

Guide

890 USE 102 00 Modicon IBM Host Based Devices Users Guide

8 90 U S E 1 03 0 0 M od icon M od bu s P l u s N e t wor k B M8 5 B r id ge

Multiplexer Users Guide

G M-H B DS -0 02 M od icon D E C H o st B as ed D evice s U s er s G u id e

P I -M BU S -3 00 M od icon M od bu s P r o t ocol R efe r en ce G u id e


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Contents890 USE 100 00 v

Contents

Chapter 1Introducing the Modbus Plus Network 1. . . . . . . . . . . . . . . . . . . . . . .

1.1 In t r odu cin g t h e Modbu s P lu s N et wor k 2. . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.1.1 Modbu s P lu s Applicat ion s 2. . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.1.2 E xt en din g t h e N et wor k 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.1.3 Br idgin g N et wor ks 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.1.4 N et wor k E xample 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.2 N et wor k Ter min ology 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.3 Over view of t h e Logical N et wor k 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.4 Over view of t h e P h ysical N et wor k 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.5 Major Com pon en t s of t h e N et wor k 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.5.1 P r ogr am m able Con t r oller s 10. . . . . . . . . . . . . . . . . . . . . . . . . . .

1.5.2 N et wor k Opt ion Modu les 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.5.3 DIO Dr op Adapt er s 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.5.4 Available Backplan es for DIO Applicat ion s 13. . . . . . . . . . . . .

1.5.5 Ter m in al Block I/O (TIO) Modu les 13. . . . . . . . . . . . . . . . . . . .

1.5.6 N et wor k Adapt er s for H ost Compu t er s 14. . . . . . . . . . . . . . . .

1.5.7 BM85 Br idge Mu lt iplexer 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.5.8 BP 85 Br idge P lu s 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.5.9 RR85 Repeat er 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.6 H ow N odes Access t h e N et wor k 18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1 .6 .1 H o w You r Ap plica t ion s L ayo u t Affe ct s N od e Acce ss 1 8. . . . .

1.6.2 Th e Token Rot at ion Sequ en ce 18. . . . . . . . . . . . . . . . . . . . . . . .

1.6.3 Poin t t o Poin t Message Tr an sact ion s 19. . . . . . . . . . . . . . . . . .1.6.4 Global Dat abase T r an sact ion s 19. . . . . . . . . . . . . . . . . . . . . . . .

1.7 E r r or Ch eckin g an d Recover y 21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.8 Design in g for P r ocess Speed 22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.9 Design in g for Det er min ist ic I/O Ser vicin g 23. . . . . . . . . . . . . . . . . . . . . . . . .

1.10 Usin g Peer Cop 24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.10.1 Peer Cop T r an sact ion s 24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.10.2 A Peer Cop E xam ple 26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


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890 USE 100 00vi Contents

Chapter 1Introducing the Modbus Plus Network (Continued):

1.11 E xpan din g t h e N et wor k 28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.11.1 Lin ear E xpan sion 28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.11.2 Usin g RR85 Repeat er s 29. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.11.3 E xpan din g Du al-cable N et wor ks 30. . . . . . . . . . . . . . . . . . . . . .

1.11.4 N on ---Lin ear E xpan sion 30. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.12 J oin in g Modbu s P lu s N et wor ks 32. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.12.1 H ow t h e Br idge P lu s Oper at es 32. . . . . . . . . . . . . . . . . . . . . . . .

1.12.2 Usin g t h e Br idge P lu s 34. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.13 Br idgin g Modbu s P lu s an d Ser ial Devices 36. . . . . . . . . . . . . . . . . . . . . . . . . .

1.13.1 H ow t h e Br idge Mu lt iplexer Oper at es 36. . . . . . . . . . . . . . . . . .

1.13.2 Modbu s Con figu r at ion s 36. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.13.3 Modbu s Por t Mappin g 37. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.13.4 RS232 an d RS485 Con figu r at ion s 38. . . . . . . . . . . . . . . . . . . . .


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Chapter 2Elements of Network Planning 41. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.1 An Over view of N et wor k P lan n in g 42. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.1.1 P r epar in g a N et wor k P lan 43. . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.2 Defin in g t h e N et wor k Com pon en t s 44. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.2.1 Modbu s P lu s Tr u n k Cable 45. . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.2.2 Modbu s P lu s Dr op Cables 45. . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.2.3 Modbu s P lu s Tap 46. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.2.4 Modbu s P lu s Cable Im pedan ce Ter min at ion 46. . . . . . . . . . . .

2.2.5 Modbu s P lu s N et wor k Gr ou n din g 47. . . . . . . . . . . . . . . . . . . . .

2.3 Defin in g t h e N et wor k Layou t 48. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.3.1 Compon en t Locat ion s 48. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.3.2 E n vir on men t al Requ ir emen t s 48. . . . . . . . . . . . . . . . . . . . . . . . .

2.3.3 Addin g Ser vice Con n ect or s 49. . . . . . . . . . . . . . . . . . . . . . . . . . .

2.3.4 Du al-Cable Len gt h Con sider at ion s 49. . . . . . . . . . . . . . . . . . . .

2.3.5 E st imat in g Cable Ru n Dist an ces 50. . . . . . . . . . . . . . . . . . . . . .


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890 USE 100 00v ii i Co nt en ts

Chapter 3Estimating Network Performance 51. . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.1 Over view 52. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.1.1 You r N et wor k Per for man ce Goal an d Opt ion s 52. . . . . . . . . .

3.1.2 Design Opt ion s for I/O Ser vicin g 53. . . . . . . . . . . . . . . . . . . . . .

3.2 Fact or s for P lan n in g 54. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.2.1 N et wor k Applicat ion s 54. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.2.2 In for mat ion Requ ir em en t s 54. . . . . . . . . . . . . . . . . . . . . . . . . . .

3.2.3 Tr an sact ion Requ ir em en t s 55. . . . . . . . . . . . . . . . . . . . . . . . . . .

3.3 H ow Devices In t er act on t h e N et wor k 56. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.4 Fact or s Th at Affect Per for man ce 58. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.4.1 H an dlin g Mu lt iple Oper at ion s 58. . . . . . . . . . . . . . . . . . . . . . . .

3.4.2 P lan n in g You r Applicat ion P r ogr am 59. . . . . . . . . . . . . . . . . . .

3.5 Comm u n icat ion Pat h s an d Qu eu ein g 60. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.5.1 Pat h Types 60. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.5.2 Pat h Qu an t it ies 61. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.5.3 Qu eu ein g 61. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.6 Readin g an d Wr it in g wit h t h e MSTR 64. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.7 A Sam ple MST R Comm u n icat ion 66. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.8 Get t in g an d Clear in g St at ist ics 68. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.8.1 Local Device St at ist ics 68. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.8.2 Rem ot e Device St at ist ics 68. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.9 Readin g an d Wr it in g Global Dat a 70. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.9.1 Passin g Global Dat a Bet ween N odes 70. . . . . . . . . . . . . . . . . . .

3.10 Loadin g E ffect s in You r Applicat ion 72. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.10.1 MSTR Dat a Pat h H an dlin g Un der Loadin g 72. . . . . . . . . . . . .

3.10.2 Modbu s P or t Da ta P at h H an dlin g U nder Loa din g 73. . . . . . .3.10.3 P r ogr am Pat h H an dlin g Un der Loadin g 73. . . . . . . . . . . . . . . .

3.11 P r edict in g Token Rot at ion Time 74. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.12 For m u la for Calcu lat in g Token Rot at ion 76. . . . . . . . . . . . . . . . . . . . . . . . . .

3.13 P r edict in g MSTR Respon se T ime 78. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.14 E st imat in g Th r ou gh pu t (Wit h MST R) 82. . . . . . . . . . . . . . . . . . . . . . . . . . . .

3 .1 4.1 G r ou p in g N od es L ogica lly for I n cr e as ed T h r ou gh p ut 8 3. . . .

3.15 E st imat in g Th r ou gh pu t (Wit h Peer Cop) 84. . . . . . . . . . . . . . . . . . . . . . . . . . .

3.15.1 E st im at in g Tot al Com mu n icat ion T ime 84. . . . . . . . . . . . . . . .

3 .1 5.2 E s t im a t in g S pe ci fic I n pu t a n d S pe cific O u t p u t T im e s 8 5. . . .

3.15.3 An E xample of Peer Cop Per for m an ce 85. . . . . . . . . . . . . . . . .


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3.16 P r edict in g N ode Dr opou t Lat en cy Tim e 86. . . . . . . . . . . . . . . . . . . . . . . . . . .

3.16.1 H ow t h e N et wor k H an dles N ode Dr opou t s 86. . . . . . . . . . . . .

3.16.2 Th e Lat en cy For m u la 86. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.17 E st im at in g Lat en cy for a Small N et wor k 88. . . . . . . . . . . . . . . . . . . . . . . . . .

3.18 E st im at in g Lat en cy for a Lar ge N et wor k 90. . . . . . . . . . . . . . . . . . . . . . . . . .

3.19 P lan n in g for Rin g J oin Time 92. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.19.1 Addin g or Delet in g N odes 93. . . . . . . . . . . . . . . . . . . . . . . . . . . .3.20 P r ecau t ion s for H ot St an dby Layou t s 94. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.21 Gu idelin es for a Sin gle N et wor k 96. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.21.1 Usin g MST R F u n ct ion s 96. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.21.2 U sin g P eer -t o-P eer Com mu n ica tion Tech n iqu es 97. . . . . . . . .

3.21.3 Usin g t h e Global Dat abase 97. . . . . . . . . . . . . . . . . . . . . . . . . . .

3.21.4 Secu rit y Con sider at ion s in N ode Addr essin g 98. . . . . . . . . . . .

3.21.5 Select in g N ode Addr esses for Best T hr ou gh pu t 98. . . . . . . . .

3.21.6 Con sist en cy in N ode Addr essin g 99. . . . . . . . . . . . . . . . . . . . . .

3.21.7 Remot e P r ogr am min g 99. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.21.8 Con t r ollin g t h e Seq ue ncin g of MST R F u n ct ion s 100. . . . . . . . .

3.21.9 Opt im izin g N ode Cou n t s 100. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.21.10 P r ior it izin g an d Com pr essin g Dat a 100. . . . . . . . . . . . . . . . . . . .

3.21.11 Select in g Br idge Mu lt iplexer P or t Modes 101. . . . . . . . . . . . . . .

3.22 Gu idelin es for Mu lt ipleN et wor ks 102. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.22.1 Br idge Com mu n icat ion Pat h s 102. . . . . . . . . . . . . . . . . . . . . . . . .

3.22.2 Usin g Mu lt iple Br idges Bet ween N et wor ks 104. . . . . . . . . . . . .

3.23 Sam ple Comm u n icat ion s Acr oss N et wor ks 106. . . . . . . . . . . . . . . . . . . . . . . .

3.24 A Su m mar y of N et wor k P lan n in g 108. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.24.1 An alyzin g You r N eeds 108. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3 .24 .2 F in d in g O pp or t u n it ie s for I n cr ea sin g P er for m a n ce 1 08. . . . . .


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Chapter 4Documenting the Network Layout 111. . . . . . . . . . . . . . . . . . . . . . . . . . .

4.1 Docu m en t in g You r N et wor k Layou t 112. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.2 Wor ksh eet s for N et wor k P lan n in g 113. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.3 Defin in g You r N ode Requ ir emen t s 114. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.4 Topology P lan n in g Wor ksh eet 116. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.5 E st imat in g Cable Len gt h s 118. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.6 Reviewin g You r Topology P lan 119. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.7 Det ailin g t h e N et wor k Layou t 120. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.7.1 O ve rvie w of You r Det aile d P la n nin g Wor k sh eet s 120. . . . . . . .

4.8 N et wor k P lan n in g Wor ksh eet 122. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.9 Cable Rou t in g Wor ksh eet 125. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.10 Mat er ials Su mm ar y Wor ksh eet 128. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chapter 5Installing the Network Cable 131. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.1 Over view of t h e Cable In st allat ion 132. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.2 Tools an d Test E qu ipmen t Requ ir ed 133. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.3 Befor e You St ar t 134. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.4 Rou t in g t h e Cables 135. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.5 Mou n t in g t h e Taps 137. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.6 Con n ect in g t h e Tr u n k Cables 138. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.6.1 Cable E nt ry an d J u mper s (Taps at In lin e Sit es) 138. . . . . . . . .

5.6.2 Cable E nt ry an d J um per s (Taps at E nd Sit es) 138. . . . . . . . . .

5.6.3 Con n ect in g t h e Wir es 139. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.7 Con n ect in g t h e Dr op Cable 140. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.7.1 Con n ect in g t h e Sign al Wir es 140. . . . . . . . . . . . . . . . . . . . . . . . . .

5.7.2 Con n ect in g t h e Ou t er Sh ield Wir e 141. . . . . . . . . . . . . . . . . . . . .

5.8 Gr ou n din g 142. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.9 Labelin g 143. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.10 Ch eckin g t h e Cable In st allat ion 144. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.10.1 In spect in g t h e Cable In st allat ion 144. . . . . . . . . . . . . . . . . . . . . .

5.10.2 Ch eckin g t h e Cable Con t in u it y 144. . . . . . . . . . . . . . . . . . . . . . . .


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Chapter 6Connecting an RR85 Repeater 147. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.1 Mou n t in g Met h ods 148. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.1.1 H or izon t al Mou n t in g 148. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.1.2 Ver t ical Mou n t in g 148. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.2 Mou n t in g Dim en sion s 149. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.3 In st allin g t h e Repeat er 150. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.3.1 Mou n t in g t h e Repeat er 150. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.3.2 Con n ect in g Power 150. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.3.3 Con n ect in g t h e N et wor k Cables 151. . . . . . . . . . . . . . . . . . . . . . .

6.4 Readin g t h e N et wor k In dicat or s 153. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.5 RR85 Repeat er Specificat ion s 154. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chapter 7Connecting a BP85 Bridge Plus 155. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.1 Mou n t in g Met h ods 156. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.1.1 H or izon t al or Ver t ical Mou n t in g 156. . . . . . . . . . . . . . . . . . . . . .

7.1.2 Rack Mou n t in g 156. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.1.3 Br idge P lu s Models 157. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.2 Dim en sion s (Pan el/Sh elf Models) 158. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.3 Dim en sion s (Rack Mou n t Model) 159. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.4 Set t in g t h e Modbu s P lu s Addr esses 160. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.5 Con n ect in g t h e Power Cables 162. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.5.1 Con n ect in g AC Power 162. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.5.2 Con n ect in g DC Power 162. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.5.3 Befor e You Apply Power 163. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.6 Con n ect in g t h e N et wor k Cables 164. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.7 Applyin g Power 165. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.8 Readin g t h e N et wor k In dicat or s 166. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.9 At t ach in g Por t Iden t ificat ion Labels 167. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.10 BP 85 Br idge P lu s Specificat ion s 168. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


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Appendix AModbus Plus Transaction Elements 171. . . . . . . . . . . . . . . . . . . . . . . . . .

A .1 Transaction Timing Elements 172. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A .1.1 Token H olding Time 172. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A .1.2 Worst Case Timing Examples 172. . . . . . . . . . . . . . . . . . . . . . . . . . .

A .1.3 Data Response Time 174. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A .2 The Message Format --- H DLC Level 176. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A .2.1 H DLC Fields 176. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A .3 The Message Format --- MAC Level 178. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A .3.1 MAC Fields 178. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A .4 The Message Format --- LLC Level 180. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A .4.1 LLC Fields 181. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Appendix BMessage Routing 183. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

B .1 The Modbus Plus Message Routing Path 184. . . . . . . . . . . . . . . . . . . . . . . . . . . .

B .2 Modbus Address Conversion 186. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

B .3 Controller Bridge Mode Routing 188. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .B .4 Bridge Multiplexer Routing 190. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

B .4.1 Rou t in g E xam ples 192. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Appendix CPlanning Worksheets 195. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

C .1 U sing the Worksheets 196. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


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Appendix DInstalling Custom Cable Systems 207. . . . . . . . . . . . . . . . . . . . . . . . . . . .

D .1 Overview 208. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

D .2 Tools and Test E quipment Required 209. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

D .3 Before You Start 210. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

D .4 Routing the Cable 211. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

D .5 Installing Connectors on Dual-Cable Runs 213. . . . . . . . . . . . . . . . . . . . . . . . . . .D .6 Installing Connectors With the Tool 214. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

D .6.1 Before You Start 214. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

D .6.2 Overview of the Connector Installation 215. . . . . . . . . . . . . . . . . . .

D .6.3 Preparing the Cable 216. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

D .6.4 Placing the Connector into the Tool 216. . . . . . . . . . . . . . . . . . . . .

D .6.5 D etermining the Wiring Direction 217. . . . . . . . . . . . . . . . . . . . . . .

D .6.6 Placing the Wires into the Connector 217. . . . . . . . . . . . . . . . . . . .

D .6.7 Replacing the Cap 218. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

D .6.8 Se ating the Wir es and I nsta lling the Cap Scr ew 218. . . . . . . . . . . .

D .6.9 Completing the Installation 219. . . . . . . . . . . . . . . . . . . . . . . . . . . .

D .6.10 What to Do Next 220. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

D .7 Installing Connectors Without the Tool 221. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .D .7.1 Before You Start 221. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

D .7.2 Overview of the Connector Installation 222. . . . . . . . . . . . . . . . . . .

D .7.3 Preparing the Cable 222. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

D .7.4 Identifying the Terminals 223. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

D .7.5 Connecting the Wires 223. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

D .7.6 Inspecting the Connection 225. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

D .7.7 Replacing the Cap 225. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

D .7.8 Completing the Installation 226. . . . . . . . . . . . . . . . . . . . . . . . . . . .

D .7.9 What to Do Next 227. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

D .8 Grounding 228. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

D .9 Labeling 229. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

D .10 Checking the Cable Installation 230. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .D .10.1 Inspecting the Cable Installation 230. . . . . . . . . . . . . . . . . . . . . . . .

D .10.2 Checking the Cable Continuity 230. . . . . . . . . . . . . . . . . . . . . . . . .

Glossary 233. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Index 242. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


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Illustrations

F igu r e 1 N et wor k Over view 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 2 St an dar d N et wor k Ter min ology 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 3 Dist r ibu t ed I/O N et wor k Ter m in ology 5. . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 4 Token Rot at ion Sequ en ce 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 5 Cable Tap Layou t 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 6 Sect ion P h ysical Layou t (Sin gle Cable) 9. . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 7 Sect ion P h ysical Layou t (Du al Cables) 9. . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 8 N et wor k Opt ion Modu le 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 9 DIO Dr op Adapt er 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 10 TIO Modu le 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 11 Exam ple of t he SA85 an d H ost Con figu rat ion 14. . . . . . . . . . . . . . . . .

F igu r e 12 H ier a rch ica l Con figu r at ion for I mp rove d T h rou gh pu t 22. . . . . . . . . .

F igu r e 13 N et wor k for Det er m in ist ic I/O T imin g 23. . . . . . . . . . . . . . . . . . . . . . .

F igu r e 14 Peer Cop E xam ple 26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 15 Basic Con figu r at ion E xam ple 28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu re 16 Ma xim um Lin ea r Con figu r at ion of a Sin gle N et wor k 29. . . . . . . . . .

F igu r e 17 P lacin g Repeat er s on Du al-cable N et wor ks 30. . . . . . . . . . . . . . . . . . .

F igu r e 18 N on ---Lin ear E xpan sion 31. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 19 Message Rou tin g Th r ou gh Mu lt iple N et wor ks 32. . . . . . . . . . . . . . . .

F igu r e 20 Message F r ame Rou t in g Pat h F ield 33. . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 21 Basic H ier ar ch ical Con figu r at ion 34. . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 22 Modbu s Devices Mu lt iplexed t o Modbu s P lu s 36. . . . . . . . . . . . . . . . .

F igu r e 23 Un iqu e Device Addr essin g an d Par amet er s 38. . . . . . . . . . . . . . . . . . .F igu r e 24 User ---pr ogr am med BM85 Applicat ion 40. . . . . . . . . . . . . . . . . . . . . . .

F igu r e 25 N et wor k Cable Syst em Com pon en t s 44. . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 26 Du al-Cable Layou t : Illegal Len gt h s 50. . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 27 Con cu r r en t Mu lt iple Oper at ion s 56. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 28 H an dlin g Mu lt iple Oper at ion s 58. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 29 BP 85 Br idge P lu s Qu eu ein g 62. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 30 MST R F u n ct ion For mat 64. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


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F igu r e 31 Sam ple RE AD Comm u n icat ion 66. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 32 Sam ple GE T LOCAL STAT ISTICS 68. . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 33 Sam ple GE T RE MOTE STATIST ICS 68. . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 34 Sam ple Global Dat abase Pass 70. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 35 Token Rot at ion Tim e 74. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 36 P r edict in g Respon se Time 79. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 37 N ode Th r ou gh pu t 82. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 38 E xample: E st imat in g Peer Cop Per for m an ce 84. . . . . . . . . . . . . . . . .

F igu r e 39 P r edict in g N ode Dr opou t Lat en cy T ime 87. . . . . . . . . . . . . . . . . . . . . .

F igu r e 40 P lan n in g for Rin g J oin T ime 92. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 41 H ot St an dby Rin g J oin Tim e 94. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 42 Br idge Com m u n icat ion Pat h s 102. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 43 Mu lt iple Br idgin g Bet ween N et wor ks 104. . . . . . . . . . . . . . . . . . . . . . . .

F igu re 44 Sam ple RE AD Com mu nicat ion Acr oss N et wor ks 106. . . . . . . . . . . . . .

F igu r e 45 E xample: N ode P lan n in g Wor ksh eet 115. . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 46 E xample: Topology P lan n in g Wor ksh eet 117. . . . . . . . . . . . . . . . . . . . .

F igu r e 47 Over view of P lan n in g Wor ksh eet s 121. . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 48 E xample: N et wor k P lan n in g Wor ksh eet 124. . . . . . . . . . . . . . . . . . . . .

F igu r e 49 E xample: Cable Rou t in g Wor ksh eet 127. . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 50 E xample: Mat er ials Su m mar y Wor ksh eet 130. . . . . . . . . . . . . . . . . . . .

F igu r e 51 Typical Cable Rou t in g 135. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 52 Tap Layou t (Cover Open ) 137. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 53 Trunk Cable Connections and Jumpers Removed (Inline Sites) 138.

F i gu r e 5 4 T r u n k C ab le C on n e ct ion s a n d J u m p e r s I n s t al le d ( E n d S it e s) 1 38. . .

F igu r e 55 Tr u n k Cable Con n ect ion s 139. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 56 Wir e Ter min al Con n ect ion (Det ail) 139. . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 57 Dr op Cable Con n ect ion s 141. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 58 Wir e Ter min al Con n ect ion (Det ail) 141. . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 59 T yp ica l Ca ble Sys tem : P oin t -t o-P oin t Con n ect ion s 145. . . . . . . . . . . .

F igu r e 60 RR85 Repeat er Mou n t in g Dimen sion s 149. . . . . . . . . . . . . . . . . . . . . . .


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F igu r e 61 RR85 Repeat er Rear Pan el View 151. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 62 RR85 Repeat er In dicat or s 153. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 63 BP 8 5 Br idge P lu s Dim en sion s (P an el/Sh elf Mod els ) 158. . . . . . . . . . .

F igu re 64 BP 85 Br idge P lu s Dim en sion s (R ack Mou n t Model) 159. . . . . . . . . . .

F igu r e 65 BP 85 N et wor k Addr ess Swit ch Set t in gs 161. . . . . . . . . . . . . . . . . . . . . .

F igu r e 66 BP 85 Br idge P lu s Con n ect or s 163. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 67 BP 85 Br idge P lu s In dicat or s 166. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 68 Modbu s P lu s Por t Labels 167. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu re 69 T im in g E lem en t s of a RE AD or WRIT E T ra nsa ct ion 175. . . . . . . . . . .

F igu r e 70 Typical Message For mat 176. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 71 MAC Level Message For m at 178. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 72 LLC Level Message For m at 180. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 73 Message F r ame Rou t in g Pat h F ield 184. . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 74 Modbu s t o Modbu s P lu s Addr ess Con ver sion 187. . . . . . . . . . . . . . . . .

F igu re 75 Con tr oller Br idge Mode Addr ess Con ver sion 188. . . . . . . . . . . . . . . . . .

F igu r e 76 Br idge Mu lt iplexer Addr ess Con ver sion 190. . . . . . . . . . . . . . . . . . . . . .

F igu r e 77 Rou t in g E xam ples 192. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 78 N ode P lan n in g Wor ksh eet 197. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 79 N ode P lan n in g: N ot es 198. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 80 Topology P lan n in g Wor ksh eet 199. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 81 Topology P lan n in g: N ot es 200. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 82 N et wor k P lan n in g Wor ksh eet 201. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 83 N et wor k P lan n in g: N ot es 202. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 84 Cable Rou t in g Wor ksh eet 203. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 85 Cable Rou t in g: N ot es 204. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 86 Mat er ials Su m mar y Wor ksh eet 205. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 87 Mat er ials Su m mar y: N ot es 206. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 88 Typical Cable Dr ops 211. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 89 Modbu s P lu s Con n ect or In st allat ion Tool 214. . . . . . . . . . . . . . . . . . . . .

F igu r e 90 Modbu s P lu s Con n ect or s 215. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


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Contents890 USE 100 00 xvii

F igu r e 91 P r epar in g t h e Cable 216. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 92 P lacin g t h e Con n ect or in t o t h e Tool 216. . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 93 Det er m in in g t h e Wir in g Dir ect ion 217. . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 94 Replacin g t h e Cap 218. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu re 95 Seat in g t he Wir es an d In st allin g t he Cap Scr ew 218. . . . . . . . . . . . . . .

F igu r e 96 Ch eckin g Wir in g Con t in u it y 219. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 97 Modbu s P lu s Con n ect or s 221. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 98 P r epar in g t h e Cable 222. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 99 Iden t ifyin g t h e Ter m in als 223. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 100 Con n ect in g t h e Wir es 224. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F igu r e 101 Con n ect in g t he Secon d Ca ble (In lin e Sit es On ly) 225. . . . . . . . . . . . .

F igu r e 102 Ch eckin g Wir in g Con t in u it y 226. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


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Introducing the Modbus Plus Network890 USE 100 00 1

Chapter 1Introducing the Modbus PlusNetwork

VIntroducing the Modbus Plus Network

V Network Terminology

V Overview of the Logical Network

V Overview of the Physical Network

V Major Component s of th e N etwork

V How Nodes Access the Network

V Err or Checking an d Recovery

V Designing for Process Speed

V Designing for Deterministic I/O Servicing

V Using Peer Cop

V Expanding the Network

V Joining Modbus Plus Networks

V Bridging Modbus Plus and Serial Devices


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2 Introducing the Modbus Plus Network 890 USE 100 00

1.1 Introducing the Modbus Plus Network

1.1.1 Modbus Plus Applications

Modbus Plus is a local area network system for industrial control

applications. Network ed devices can exchan ge messages for th e cont roland monitoring of processes at remote locations in the industrial plant.

Modicon products supporting Modbus Plus communication include

programm able controllers and n etwork adapter s. The n etwork is also

supported by a variety of products from other manu facturers.

Each Modicon controller can connect to Modbus Plus directly from a

port on its front pan el. Additional network s can be accessed thr ough

Network Option Modules (NOMs) installed in the common backplane.

The network also provides an efficient means for servicing input/output

subsystems. Modicon Modbus Plu s Distr ibuted I/O (DIO) Drop Adapter s

and Terminal Block I/O (TIO) modules can be placed at remote I/O sitesto allow the application to control field devices over the network link.

1.1.2 Extending the Network

Each n etwork supports up to 64 addressable node devices. Up t o 32

nodes can connect directly to the network cable over a length of 1500 ft

(450 meters). Repeaters can extend th e cable distance to its m aximum

of 6000 ft (1800 meters) and t he n ode count to its maximum of 64. Fiber

optic repeaters are available for longer distances.

1.1.3 Bridging Networks

Multiple net works can be joined th rough Bridge Plus devices. Messages

originated on one net work are r outed thr ough one or more bridges to a

destinat ion on an other n etwork. Bridges are applicable to networks in

which fully deterministic timing of I/O processes is not a requirement.

In a network requiring deterministic I/O timing, messages for DIO/TIO

nodes are passed on th at network only, and do not pass th rough bridges.

Modbus and custom RS232/RS485 serial devices can access Modbus P lus

th rough Br idge Multiplexers. Each Bridge Multiplexer provides four

configur able serial port s. A serial device can commun icate with Modbus

Plus networked devices, as well as with other devices at the serial ports.


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1.1.4 Network Example

Figure 1 shows four Modbus Plus n etworks. A Repeater extends the

cable for N etwork A. Net works A and B ar e joined by a Bridge Plus.

Networks C and D h andle I/O processes. DIO Drop Adapters and

Termin al Block I /O modules service the I/O field devices at each site.

BP85BRIDGE

PLUS

RR85REPEATER

HOST DEVICENETWORKADAPTER

BM85BRIDGE

MULTIPLEXER

MODBUS OR CUSTOMSERIAL DEVICES

HOSTCOMPUTER

CPU

NOM

PS

I/OMODULES

UP TO64

NODESTOTAL

UP TO 64NODESTOTAL

UP TO 64NODESTOTAL

UP TO64

NODESTOTAL

CPU CPU

NETWORK A

NETWORK B

NETWORK C

NETWORK D

DI

O

DI

O

TIO

TIO TIO

NOM

I/OMODULES

I/OMODULES

USERINTERFACE

Figure 1 Network Overview


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1.2 Network Terminology

The following terms are used in this guide to describe network elements:

N e t w o r k The grouping of nodes on a common signal path that is accessed by t he

passing of a t oken. It consists of one or more cable sections . For

example, all of the nodes in F igure 2 are on a network.

NODE5

NODE2

NODE64

NODE10

REPEATER

NODE23

NODE14

NODE

NODE

NODENODE NODE

NODE NODE

SECTIONCABLESEGMENT

DEVICESARE ON

TWO SECTIONSOF

ONE NETWORK

Figure 2 Standard Network Terminology

S e c t i o n A series of nodes th at are joined only by cable segments. The sections

signal path does n ot pass t hrough any kind of node device. Sections ar e

all part of one network, sharing the same token and address sequence.

In F igure 2, the Repeater joins two sections. Each section can be up to

1500 ft (450 m) long, and can contain up to 32 physical node

connections.

C a b l e S e g m e n t A single length of tru nk cable between two taps. Taps are passivedevices that provide connections for the trunk cable segments.

In Figure 2, the cable connection between th e nodes at addresses 10

and 5 is th rough one cable segm ent. Another cable segm ent connects

nodes 5 and 64.

On dual-cable networks, two cable segm ents run in parallel between

pairs of nodes.


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N o d e Any device that is physically connected to the Modbus Plus cable.

Figure 2 shows a network with seven node devices. The ter m applies to

any device, whether it is addressable or not. Some nodes, like

programm able contr ollers, have addresses an d can serve as sources or

destinations for messages. The Bridge Plus is a separately addressable

node on each of its two networks. The Repeater is a node on each of

two sections, but has no address, serving only to extend the network.

T o k e n A grouping of bits that is passed in sequence from one device to

another on a single network, to gran t access for sending messages. If

two networks ar e joined by a Bridge Plus, each n etwork has its own

token that is passed only among the devices on that network.

D I O N e t w o r k A Distributed I/O (DIO) network is a Modbus Plus network designed

primar ily for ser vicing I/O field devices in t he a pplication. In its

minimum configuration a DIO network consists of one controller (CPU)

and one or more drops located at remote sites n ear to th e field devices.

Each drop consists of a DIO Drop Adapter installed in a backplane with

I/O modules, or a Terminal Block I/O (TIO) module.

In Figure 3, one DIO network contains the CPU, a DIO Adapter, and a

TIO module. Two other DIO networks consist of Network Option

Modules (NOMs) with DIO Drop Adapters an d T IO m odules.

Details for designing a Modbus Plus n etwork th at is intended primarily

for I/O servicing are in the Modbus Plus N etwork I/O S ervicing Guide.

CPU

NOM

PS

I/OMODULES

UP TO 64NODES TOTAL

UP TO 64NODES TOTAL

UP TO 64NODES TOTAL

DI

O

DI

ODI

O

NOM

TIOI/O

MODULES

I/OMODULES

I/OMODULES

TIO

TIO

Figure 3 Distributed I/O Network Terminology


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1.3 Overview of the Logical Network

Net work nodes are identified by addresses assigned by th e user. Each

nodes address is independen t of its ph ysical site location. Addresses are

within the ran ge of 1 to 64 decimal, and do not h ave to be sequential.

Duplicate addresses are not allowed.

Network nodes function as peer members of a logical ring, gaining access

to the n etwork u pon receipt of a token frame. The token is a grouping of

bits that is passed in a rotating address sequence from one n ode to

another. Each network maintains its own token r otation sequence

independent ly of the other networks. Where multiple networks are

joined by bridges, the token is not passed through the bridge device.

While holding the token, a node initiates message transactions with

other n odes. Each message contains rout ing fields that define its source

and destinat ion, including its r outing path thr ough bridges to a node on

a remote network.

When passing th e token, a node can write into a global database that isbroadcast to all nodes on the n etwork. Global data is transmitted as a

field within t he token frame. Other n odes monitor the token pass and

can extract th e global data if they have been programmed to do so. Use

of the global database allows rapid updating of alarms, setpoints, and

other data. Each network maintains its own global database, as the

token is not passed thr ough a bridge to another network.


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Figure 4 shows the token sequences in two networks joined by a

Bridge Plus.

NODE

BRIDGEPLUS

NETWORK 1

NODE NODE NODE

NODE NODE NODE NODE

NETWORK 2

2 12

22

10 5

5 10

24

4 9

TOKEN SEQUENCE: 2 -- 5 -- 10 -- 12 -- 22 -- 2 . . .

TOKEN SEQUENCE: 4 -- 5 -- 9 -- 10 -- 24 -- 4 . . .

Figure 4 Token Rotation Sequence


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1.4 Overview of the Physical Network

The network bus consists of twisted-pair shielded cable that is run in a

direct path between su ccessive nodes. Th e two data lines in th e cable

are not sensitive to polarity, however a standard wiring convention is

followed in t his guide t o facilitate maint enan ce.

The network consists of one or more cable sections, with any section

supporting up to 32 nodes at a maximum cable distance of 1500 ft

(450 m). Sections can be joined by Repeaters t o extend the network

length and t o support up to 64 nodes.

The m inimum cable length between an y pair of nodes must be at least

10 ft (3 m). The m aximum cable length between two nodes is th e same

as the maximum section length of 1500 ft (450 m).

On dual-cable networks, the cables are known as cable A and cable B.

Each cable can be up to 1500 ft (450 m) long, measured between the two

extrem e end devices on a cable section. Th e difference in lengt h

between cables A and B must not exceed 500 ft (150 m), measuredbetween any pair of nodes on the cable section.

Nodes are connected to the cable by means of a tap device, supplied by

Modicon. This provides th rough conn ections for th e network tr un k

cable, drop connections for t he cable t o th e n ode device, and a

grounding terminal.

The tap also cont ains a resistive termination t hat is connected by two

intern al jumpers. The t ap at each en d of a cable section requires both of

its jumpers t o be connected t o prevent signal reflections. All of the t aps

that are inline on th e cable section require th eir jumpers to be removed

(open).

Figure 5 illustrates a t ap at an inline site. Two lengths of tru nk cable

are inst alled. When a ta p is inst alled at t he end site of a cable section,

only one length of trun k cable is routed to the tap. It can enter at either

side of the t ap. The jumpers are conn ected to the signal pins at th e

opposite side of the t ap to pr ovide the n etwork terminat ion.


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NETWORKTRUNKCABLE

NETWORKTRUNKCABLE

DROPCABLE

TO NODE

TAP SHOWNWITH

COVER OPEN

CABLETIE

TERMINATIONJUMPERS (2)

-- -- --END SITES: CONNECTED

TO PINS AT OPPOSITE SIDEFROM TRUNK CABLE ENTRY

-- -- --INLINE SITES: OPEN

GROUNDWIRE

Figure 5 Cable Tap Layout

The next two figures summarize the layout for one section of a network.

10 ft (3 M) CABLE MIN.

= JUMPERS CONNECTED = JUMPERS DISCONNECTED

END INLINENODENODE

ENDNODE

INLINENODE

UP TO 32 NODES MAX., 1500 ft (450 M) CABLE MAX.

Figure 6 Section Physical Layout (Single Cable)

= JUMPERS CONNECTED = JUMPERS DISCONNECTED

END INLINENODENODE

ENDNODE

INLINENODE



500 ft (150 M) MAX. DIFFERENCE BETWEEN CABLES A AND BMEASURED BETWEEN ANY PAIR OF NODES

CABLE A

CABLE B

Figure 7 Section Physical Layout (Dual Cables)


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1.5 Major Components of the Network

1.5.1 Programmable Controllers

Modicon controllers connect directly to the network bus cable through a

dedicated Modbus Plus communication port that is located on thecont roller assem bly. The port allows the contr oller to commu nicate with

other n etworked cont rollers, host computers with network adapters, an d

DIO drops.

Contr oller models are available for single-cable an d du al-cable n etwork

layout s. Contact your Modicon distribut or for informat ion about m odels

and part nu mbers.

Each controller functions as a peer on the network, receiving and

passing tokens and messages. Th e user application program can access

registers in the local controller and in the other networked controllers.

Three types of communication are available to the application programfor exchanging messages between networked nodes:

V The MSTR fun ction block can be u sed for tran sferring, reading and

clearing statistics, and accessing t he networks global database. The

MSTR is a general function for tran sacting messages with any t ype

of networked node. It is programmed into th e user logic program of

the controller.

V Peer Cop tr ansfers can be used to move data both globally and with

specific nodes. Such t ran sfers are specified in t he contr ollers Peer

Cop table during its initial configuration.

V Distributed I/O transfers can be used to move data with DIO DropAdapter nodes. Such tr ansfers are specified in the contr ollers DIO

Map table during its initial configuration.

Hot Standby ConfigurationsWhen two contr ollers are conn ected in a redundan t (hot standby)

configuration, each controller is seen as a separate address on the

net work. This use of dual addressing allows both cont rollers to be fully

accessed for programm ing and stat istics. If a tr ansfer occurs to th e

standby contr oller, the primary an d stan dby addresses ar e exchan ged,

maintaining consistent addressing within the application.


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N o t e : The address exchange can cause a moment ary delay in

communication with the new primary unit while it assumes its place in

the n etwork token r otation sequence. This can be a significant factor

in th e timing of processes using r edundant contr ollers. The application

should provide retry capabilities in the other nodes to cover this t ime.

1.5.2 Network Option Modules

The N etwork Option Module (NOM) mounts in th e backplane with th e

controller. It allows the user application program, run ning in t he

controller, to communicate with an additional Modbus Plus network.

The additional network can be configured with controllers, other NOMs,

Distribut ed I/O nodes, or a combination of th ese devices. One or t wo

NOMs can be mounted in t he contr ollers housing. Power is taken from

the power supply module which must also be installed in the housing.

Network Option Modules ar e available for sin gle-cable an d du al-cable

net work layouts. Contact your Modicon distributor for informat ion

about models and part numbers.

Modbus

Connector

Modbus PlusConnectorChannel A

Modbus PlusConnectorChannel B

(Cover Open)

NOTENOTE

Network Option Modules are available for eithersingle-cable or dual-cable network layouts.The dual-cable model is shown.

Modbus PlusAddress Switches

(on rear)

Figure 8 Network Option Module


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1.5.3 DIO Drop Adapters

The DIO Drop Adapter moun ts in a housing at a r emote site,

communicating over the housing backplane to the sites I/O modules to

service the sites data requirements. The adapter includes a built-in

power supply that provides operating power for the I/O modules.

DIO Adapters are available for single-cable an d du al-cable n etwork

layout s. Contact your Modicon distribut or for informat ion about m odelsand part nu mbers.

Figure 9 shows the front view of a typical DIO Drop Adapter.

Specifications a re provided in th e Quantum Automation S eries

Hardw are R eference Gu ide.

Power/GroundTerminal Strip

(Cover Open)

Modbus PlusConnectorChannel A

Modbus PlusConnectorChannel B

NOTE

DIO Drop Adapters are available for eithersingle-cable or dual-cable network layouts.

The dual-cable model is shown.


(on rear)

Figure 9 DIO Drop Adapter


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1.5.4 Available Backplanes for DIO Applications

Modicon backplan es are a vailable in sizes from 2 ... 16 slots. The DIO

Drop Adapter module occupies one slot, and contains a power supply

that furnishes operating power t o the housing for I/O modules. The

supplys capacity is 3.0 A.

1.5.5 Terminal Block I/O (TIO) ModulesRemote sites can be serviced using Terminal Block (TIO) modules.

These compact modules mount directly to a panel or DIN rail, and

provide direct wiring conn ections to field devices at th e site.

TIO modules ar e available for single-cable layout s only, an d ar e n ot

applicable for use in dual-cable layouts.

Figure 10 sh ows the front view of a typical TIO m odule. Specifications

are in th e Terminal Block I/O Modules Hardware Reference Guide.

Modbus PlusConnector

Label forField Wiring

Field WiringConnectors

Slots for

NOTE

TIO modules are available for single-cablelayouts only.


Figure 10 TIO Module


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1.5.6 Network Adapters for Host Computers

Adapters are available for connecting host computers to the Modbus

Plus n etwork. The SA85 Network Adapter conn ects an IBM AT or

compatible product t o the n etwork. The SM85 Network Adapter

connects an IBM Personal System/2 or compatible product using a

MicroChan nel bus. The SQ85 connects a DEC MicroVAX II or 3000.

Figure 11 shows an example of the configuration of an SA85 adapter intoan IBM AT-compatible host computer.

AM--SA85--002

DEVICEDRIVER

MODBUS PLUS NETWORK

SINGLE CABLE

AND

NETBIOS

LIBRARY

AM--SA85--000

( OR )

DUAL CABLE

Figure 11 Example of the SA85 and Host Configuration

Adapters are supplied complete with the required device driver, a library

of C functions that can be called by the application, a network diagnostic

ut ility, and a set of sample programs. The Modbus Plus n etwork cable

connects to a communications port on the adapter.

The adapters device driver responds to a library of NetBIOS functions

that are called from t he application program. These allow sending and

receiving data packets, sending and receiving global data transactions,

and monitoring status.

Applications run ning in t he h ost computer can read an d write references

at other nodes. They can also program remote n odes and access the

global data base.


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Typical network adapter applications include:

V User interfaces

V Cont rol, monitoring, an d reporting of remote processes

V Pr ogram load/record/verify operat ions

V Online programming

V Bridging between Modbus Plus and other networks

V Testing and debugging of application programs

V Runn ing n etwork diagnostic programs.

Modbus comman ds received from t he Modbus Plus network t hat are

addressed to the network adapter can be given to tasks running in the

compu ter. Examples include:

V Runn ing a dat a logging t ask in the host, accessed by other nodes on

the network.

V Providing virtual registers for remote controllers.

Each adapter can be separately configured for its use of memory,

interru pts, and other par ameters. This allows flexibility in u sing

mult iple adapter s in th e same host computer. You can also apply th e

adapter as a bridge between Modbus P lus and other n etworks which

may be present, including those which may also be using NetBIOS.

Informat ion about installing t he n etwork adapters, setting th eir Modbus

Plus par ameters, an d conn ecting them to th e network, is supplied with

the adapters.


33/255


1.5.7 BM85 Bridge Multiplexer

Th e BM85 Bridge Multiplexer pr ovides conn ection to Modbus P lus for

up t o four kin ds of serial devices. Four BM85 models are available. Two

of these connect Modbus devices, or net works of Modbus devices, to th e

Modbus Plus n etwork. Each of the Modbus ports can be separately

configured to support a Modbus master device, slave device, or network

of slave devices. Port param eters a re also separat ely configur able.

Two other BM85 models ar e available for user -defined RS232 or RS485

serial devices. Th ey include a library of C language fun ctions for

creating a user application program.

Bridge Multiplexers are available for single-cable an d du al-cable n etwork


and part nu mbers.

1.5.8 BP85 Bridge Plus

The BP85 Bridge Plus allows you to connect two Modbus Plus networks.

The routing information in each message allows a node on one networkto commu nicate t hrough t he Bridge Plus to a destination n ode on

another n etwork. Up to four bridges can be present in th e message path

between th e source and destinat ion n odes. You can t her efore join up to

five Modbus Plus networks along a linear path, with any node being able

to commu nicate with an y other n ode.

Bridge Plus devices are not applicable to Modbus Plus DIO networks

because th ose networks tr ansfer data messages as part of the token pass.

Tokens ar e not passed thr ough the Bridge Plus.

Note th at the Bridge P lus may still be placed on a DIO n etwork to allow

non-DIO messages to be passed to another network. For example,

statistical reporting can be handled between a controller on the DIO linkand a network adapter in a host processor on another network.

The Bridge Plus contains two ports, for connection to its two networks.

It functions as an addressable node on each of the two networks it joins.

It contains two sets of address switches, for setting its node address on

each n etwork. The t wo addresses can be set t o the same value, or to

different values, as they are independent of each other.

Bridge Plus models are available for single-cable an d du al-cable n etwork


and part nu mbers.


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1.5.9 RR85 Repeater

The RR85 Repeater allows you to place more than 32 nodes on the

network and to increase the cable distance up to an additional 1500 ft

(450 m). It functions as an am plifier an d signal conditioner to maint ain

adequate signal levels between its two sections of the network. Up to

three Repeaters may be present in the message path between the source

and dest ination n odes. You can th erefore join u p to four sections along a

single linear path . Oth er configur ations are possible and ar e describedlater in this chapter.

Contact your Modicon distributor for information about models and part

numbers.

In addition to its use in extending the n etwork, t he Repeater can be

applied in plant environments that have high levels of electrical

interference. Repeaters at key point s in th e cable system can h elp to

maintain an excellent signal t o noise r atio on the network.

The Repeater is provided with two ports for connection to the two

sections. It is count ed as a physical node on each section. Th e Repeater

does not have a network address. It tr ansparent ly passes tokens and

messages as they are received.

When Repeaters are used in dual-cable network layouts, one Repeater

must be positioned on each cable at t he same point (between th e same

pair of nodes) as on th e other cable. Informat ion is supplied in this

guidebook for insta lling Repeater s.


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1.6 How Nodes Access the Network

1.6.1 How Your Applications Layout Affects Node Access

When the network is initialized, each node becomes aware of the other

active nodes. Each node builds a table ident ifying th e oth er nodes.Initial ownership of the t oken is established, and a t oken rotation

sequence begins. Your choice between laying out your application as one

large network, or as several smaller networks, affects the timing of the

complete token rotation.

For example, tokens ar e not passed t hrough Bridge Plus n odes, although

messages can be addressed through Bridge Plus nodes to destination

nodes. You can ther efore const ru ct your n etworking application as

several smaller net works, joined by Bridge Plus nodes. Th e fast t oken

rotation time in each small network allows rapid transfer of

high-priority data, with lower-priority data passing through bridges to

other n etworks. Th is facilitates time-critical messaging to nodes tha t

are tightly linked in an application.

1.6.2 The Token Rotation Sequence

The t oken sequence is determined by the n ode addresses. Token

rotat ion begins at th e n etworks lowest ---addr essed active node,

proceeding consecut ively thr ough each higher ---addr essed node, u nt il the

highest ---addr essed active node receives the t oken. Tha t n ode then

passes th e token t o the lowest one to begin a n ew rotation.

If a n ode leaves t he net work, a new t oken ---passing sequ ence will be

established to bypass it, t ypically with in 100 milliseconds. If a new node

joins, it will be included in t he address sequen ce, typically with in 5

seconds (worst-case time is 15 seconds). The process of deleting an d

adding nodes is tran sparent to th e user application.

Where multiple networks are joined by bridges, tokens are not passed

thr ough a bridge device from one n etwork to another. Each network

performs its token passing process independently of the other networks.


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1.6.3 Point to Point Message Transactions

While a node holds the token, it sends its application messages if it has

any to tr ansmit. Each message can contain up t o 100 cont roller

registers (16---bit words) of data. Th e other n odes monitor th e network

for incoming messages.

When a node receives a message, it sends an immediate acknowledgment

to the originat ing node. If the message is a request for data, thereceiving node will begin assembling the requested data into a reply

message. When th e message is ready, it will be tran smitted to t he

requestor when the node receives a subsequent token gran ting it access

to tran smit.

Nodes can also transact messages containing local and remote operating

stat istics. These include inform ation such a s identification of active

nodes, curren t software version, network activity, and error reporting. If

a node transmits a request to read statistics in another node, the entire

transaction is completed while the originating node holds the token.

The r emote nodes stat istics are imbedded in its acknowledgement . It is

not necessary for the remote node to acquire the token to transmit the

statistics.

After a node sends all of its messages, it passes the token on to the next

node. Pr otocols for token passing and messaging are tr ansparent to the

user application.

1.6.4 Global Database Transactions

When a node passes the token, it can broadcast up to 32 words (16 bits

each) of global informat ion to all other nodes on the network. The

information is contained in t he t oken frame. The pr ocess of sending

global data when tran smitting th e t oken is cont rolled independently by

the application program in each node.

The global data is accessible to the application programs at the other

nodes on t he same n etwork. Each node maintains a table of global data

sent by every other n ode on the n etwork. Although only one node

accepts t he t oken pass, all nodes monitor t he t oken tr ansmission an d

read its conten ts. All nodes receive and store t he global data into t he

table.

The table contains separate areas of storage for each nodes global data.

Each nodes application program can selectively use t he global data from

specific nodes, while other applications can ignore t he dat a. Each n odes

application determines when and how to use the global data.


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Global database applications include time synchronization, rapid

notification of alarm conditions, and multicasting of setpoint values and

const ant s to all devices in a common process. This allows uniform and

rapid transmission of global data without having to assemble and

transmit separate messages to the individual devices.

Access to a net works global dat abase is available only to th e n odes on

that network, because th e token is n ot passed thr ough bridge devices to

other n etworks. The u sers application can determine which dat a items

are u seful to n odes on a remote net work, an d forward t hem as necessary.


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1.7 Error Checking and Recovery

When a node sends a data message, it expects an immediate

acknowledgment of receipt by the destin ation. If none is received, the

node will attempt up t o two retries of the message. If the final retr y is

unsu ccessful, the n ode sets an error which can be sensed by the

application program.

If a node detects a valid tran smission from an other n ode using th e same

address, the node becomes silent and sets an error which can be sensed

by the application. The n ode will remain silent as long as the du plicate

node continues to par ticipate in th e token r otation. If two devices have

been inadvertently assigned the same address, the application program

can detect the duplication and handle it while the rest of the application

continues.

When a node transmits the token, it monitors the network for new

activity from its su ccessor. If the node detects n o valid activity, it m akes

one retry t o pass the token. If no activity is detected after th e retr y, the

node remains silent. This causes th e network t o be initialized and a newtoken sequence to be created.


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1.8 Designing for Process Speed

Figure 12 is an example of a hierarchical approach using Bridge Plus

devices. The a pplication u ses a relatively large count of nodes, but n o

network contains more t han six nodes.

Token access and message han dling can be r apid within the networksth at are used for t he contr ol of time ---critical processes. For example,

the node count on a given network can be reduced to the minimum that

is required for th at portion of the application. Node counts on other

less-critical n etworks can be increased.

Message transactions across the bridges are slower than in single

networks, because th e rotation t imes of the mu ltiple networks ar e a

factor in r eceiving data r esponses from destin ations. Because of this,

intern etwork traffic should be dedicated t o tran sactions that are less

critical for timing, such as for data collection and program downloading.

BP = BRIDGE PLUS

BPBP

P230P230

BPBP

UI = USER INTERFACE HOST UI UI

UI UIUI UI

CPU

BPBP

CPU CPU CPU CPU CPU

CPU CPU CPU CPU CPU CPU

Figure 12 Hierarchical Configuration for Improved Throughput


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1.9 Designing for Deterministic I/O Servicing

Figure 13 illustrates a network designed for deterministic timing of I/O

processes. The I/O net work consists only of the CPU a nd I/O drops.

A User In terface (UI) device is conn ected t o a separat e net work at the

NOM port.

CPU NOMPS

I/OMODULES

D

IO TIO TIO

UI

MODBUSPLUS

2

3 4 5

TIO

6

MODBUSPLUS

2

3

I/OMODULES

Figure 13 Network for Deterministic I/O Timing

For truly deterministic timing of I/O servicing, reserve the CPUs

net work for t he n odes used in I/O servicing only. If you requ ire a User

Interface or other non-I/O device in your application, connect it to a

separate network at a NOM port.

Guidelines for designing net works for servicing I/O pr ocesses, withestimates of network performance, are provided in the Modbus Plus

Network I/O Servicing Guide.


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1.10 Using Peer Cop

1.10.1 Peer Cop Transactions

Point to point data can be tr ansacted while a node holds the t oken and

during its token pass with Modbus P lus Peer Cop. Up to 500 words (16bits each) can be directed t o specific data references in node devices pr ior

to release of the token, and up to 32 words can be globally broadcast to

all nodes as part of the token frame.

Because all nodes monitor t he n etwork, each n ode can extract data that

is specifically addressed to t hat node. All nodes detect the t oken pass,

and can extra ct global data messages from the token frame. Defined

data references (like controller discretes or registers) are used as sources

and destin ations. For example, a block of registers can be the dat a

source at the tran smitting node, and th e same block or another block

can be the data destination in the receiving node.

The delivery of Peer Cop data to destination nodes is independent of thenext address used in th e token pass. The t oken is always passed to the

next node in the n etworks address sequence. The token frame,

however, can contain Peer Cop global messages that are unrelated to the

next address and which are globally broadcast to all nodes.

Each node is configured through its Modicon panel software to handle

Peer Cop data tr ansa ctions. Nodes must be specifically configur ed to

send an d receive the data. Nodes which ha ve not been configured for

Peer Cop will ignore the data transactions.

Sending DataNodes can be configured to send two kinds of Peer Cop data:

V G l o b a l O u t p u t Up to 32 words of data can be broadcast globally

from each node to all nodes. Source data references are specified in

the node configuration.

V S p e c i fi c O u t p u t Up to 32 words of data can be transmitted to any

specific node. Multiple node destinations can be specified, up to th e

maximum of 500 data words. Any nodes on t he net work can be

specifically addressed as destin ations. A unique block of references

can be specified as the data source for each targeted node.


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Receiving DataNodes can be configured to receive two kinds of Peer Cop data:

V G l o b a l I n p u t Up to 32 words of global data can be received by

each n ode from each other node on t he network. Destination

references are specified in t he r eceiving nodes configur ation. Up to

eight blocks of references can be specified, giving up to eight

separate destinations for t he data received from each source n ode.

The incoming data can be indexed to establish the starting point and

length of each block of data to be extracted from t he message an d

delivered to each destination.

V S p e c i fi c I n p u t Up t o 32 words of data can be r eceived from an y

specific node. Each n ode on th e n etwork can be specifically defined

as a data source, up to the maximum of 500 data words.

The net effect of using Peer Cop for data transactions is that each

sending node can specify unique references as data sources, and each

receiving node can specify the same or different references as data

destinat ions. When r eceiving global data, each node can in dex to specific

locations in the incoming data and extract specific lengths of data from

those points. Data is thus t ran sacted rapidly as part of each token pass,

and can be directly mapped between data references in th e sending and

receiving nodes.

Applications can be designed in which alarms and setpoints are

tr ansm itted (globally), with requir ed actions by specific nodes also

defined (specifically). Because a ll nodes detect th e token passes, Peer

Cop global data can be rapidly known to all nodes, with each nodes

specific data requirements also rapidly known to just that node.

Because Peer Cop data is transacted as part of the token pass, it applies

to each n etwork independently of any other n etworks that are part of

the Modbus P lus system. Tokens ar e not exchan ged between n etworks,because th ey are not passed thr ough Bridge Plus devices. Each network

maintains its own Peer Cop database, with its own system of global

broadcasting an d specific node addressing.


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1.10.2 A Peer Cop Example

Figure 14 shows a n etwork with thr ee nodes that ar e han dling Peer Cop

data tran sfers. Other n odes are also present elsewhere on the network.

GLOBAL OUT:

NODE5

NODE7

NODE2

GLOBAL IN FROM 2:

40017--40048 (32)

GLOBAL IN FROM 18:

30010 (1)

10097--10129 (2)

40200--40202 (3)

SPECIFIC OUT TO 5:

SPECIFIC OUT TO 7:

SPECIFIC IN FROM 2:

SPECIFIC IN FROM 10:

SPECIFIC IN FROM 2:

10017--10048 (2)

10017--10048 (2)

10017--10048 (2)

40100--40131 (32)

10201--10216 (2)

TOKEN PASS (TO NODE 3)

TOKENMONITOR

TOKENMONITOR

Figure 14 Peer Cop Example

N o d e 2 curr ently holds the t oken and passes it to the next addressed

node (node 3). Nodes 5 and 7 monitor th e pass and extract data as th ey

have been configur ed to do.

Node 2 transmits two words of Specific Output for node 5 from its

references 10017 ... 10048 (32 bits of discrete reference data, a total of

two 16-bit words). It also tran smits th ese same references as Specific

Output for node 7. In th e token frame, node 2 tran smits 32 words of

Global Output from its references 40017 ... 40048.

N o d e 5 has been configured t o receive Global Input from node 2. It

places one word into its reference 30010, and two words (32 discretes)

into r eferen ces 10097 ... 10129. Node 5 indexes int o the 32 words of data

and m aps its 3 words into th ese references. Node 5 has also been

configur ed to receive Specific Inpu t from n ode 2, and places it into

references 10017 ... 10048. Note th at t he application u ses ident ical

references for this data in n odes 2 and 5. The r eferen ces could have

been different if required.


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N o d e 7 has not been configured to receive Global Input from node 2,

and ignores it. The n ode receives Specific Input and m aps it to its

references 10201 ... 10216.

O t h e r R e f er e n c e s I g n o r e d Node 5 is also configur ed t o r eceive

Specific Input from n ode 10, and node 7 is configur ed t o receive Global

Input from node 18. These other r eferences are not involved in the

tr ansa ctions from node 2. Nodes 5 and 7 could also be configured t o

make output transactions when they pass the token.


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1.11 Expanding the Network

1.11.1 Linear Expansion

The simplest network configuration consists of two or more nodes

conn ected to a single section. Figure 15 shows four n odes conn ected in abasic dual-cable configuration.

PROGRAMMABLECONTROLLER



NODE5

NODE64

NODE10

NETWORKADAPTER

NODE2



500 ft (150 M) CABLE MAX. DIFFERENCE, CABLE A TO BMEASURED BETWEEN ANY PAIR OF NODES

CABLE A

CABLE B

Figure 15 Basic Configuration Example

The basic configuration in Figure 15 will satisfy the network

requ iremen ts if all of th e following specifications are met:

V Not more than 32 nodes are connected to the network cable

V Th e t otal en d---to ---end length of each net work cable is 1500 ft

(450 m) or less

V The difference in length between cables A and B is 500 ft (150 m) or

less, between any pair of nodes

V The length of each cable segment (between a pair of nodes) is 10 ft

(3 m) or more

V The proper type of impedance termination is used at each node site

(taps inter nal jumpers r emoved at inline sites, and installed at end

sites).


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1.11.2 Using RR85 Repeaters

If your network requires more than 1500 ft (450 m) of cable, or more

than 32 nodes, you can install RR85 Repeaters t o expand t he n etwork.

The r epeaters

Documents

PLC MB+ Networking Planning & Installation Guide 4.0