Wilamowski B.M., Irwin J.D. The Industrial Electronics Handbook. Second Edition: Industrial Communication Systems

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32-10 Industrial Communication Systems

32.5.3 Status of the Controller and Fail-Safe Functionality

In.order.to.ensure.a.high.degree.of.device.interchangeability.among.devices.of.the.same.type,.the.system.

beha

vior

.of.the.DP.has.also.been.stan

dardized.

. is.beha

vior

.is.dete

rmined

.prim

arily

.by.the.oper

ating

stat

.of.the.DPM1

. is.can.be.cont

rolled

.eith

.loca

lly

.or.over.the.bus.from.the.con

guration

.devi

ce.

 ere.are.thr

.mai

.sta

tes:

Stop

.No.dat

.com

munication

.bet

ween

.the.DPM

.and.the.sla

ves.

Clear

. e.DPM1.reads.the.inpu

.info

rmation

.of.the.slav

.and.keep

.the.outp

uts

.of.the.slav

.in.

afa

il-safe

.state.(“0”.outp

ut).

Operate

. e.DPM1.is.in.the.data.tran

sfer

.phas

.In.cycl

.data.comm

unication,

.inpu

.are.read.from.

the.sla

ves

.and.out

put

.inf

ormation

.wri

tten

.to.the.sla

ves.

.DPM1.cycl

ically

.send

.its.stat

.to.all.its.assig

ned

.slav

.at.con

gurable

.inte

rvals

.using.a.mult

cast

.comm

and.

. e.reac

tion

.of.the.syst

.to.a.faul

.duri

.the.data.tran

sfer

.phas

.of.the.DPM1

.e.g.,.the.

fail

ure

.of.a.sla

ve,

.is.det

ermined

.by.the.“au

.cle

ar”

.con

guration

.par

ameter.

.this.para

meter

.is.set.to.True

.the.DPM1.swit

ches

.the.outp

uts

.of.all.assig

ned

.slav

.to.a.fail

-safe

.stat

the.mome

.a.slav

.is.no.long

.read

.for.user.data.tran

smission.

. e.DPM1.subs

equently

.swit

ches

.to.

the.clea

.stat

.If.this.para

meter

.is.set.to.Fals

.the.DPM1.rema

ins

.in.the.oper

ate

.stat

.even.in.the.even

of.a.fau

.and.the.use

.can.con

trol

.the.rea

ction

.of.the.sys

tem.

32.5.4 Diagnostics of the Field-Device

 e.comprehensive.diagnostic.functions.of.DP.enable.the.fast.location.of.faults.. e.diagnostic.messages.

are.tra

nsmitted

.ove

.the.bus.and.col

lected

.at.the.mas

ter.

. es

.mes

sages

.are.div

ided

.into.thr

.lev

els:

•

. Devi

ce-specic diagnostics:

.Mess

ages

.on.the.gene

ral

.read

iness

.for.serv

ice

.of.a.stat

ion,

.such.as.

“Ove

rheating,”

.“Un

dervoltage,”

.or.“In

terface

.unc

lear.”

•

. Modu

le-related diagnostics:

. ese.mess

ages

.indi

cate

.whethe

.a.diag

nosis

.is.pend

ing

.with

.a.

spec

ic

.I/O.subd

omain

.of.a.stat

ion

.(e.g

.8.bit.outp

.modu

le).

•

. Chan

nel-related diagnostics:

. ese.mess

ages

.indi

cate

.the.caus

.of.a.faul

.rela

ted

.to.an.indi

vidual

inpu

t/output

.bit.(ch

annel),

.suc

.as.“Sh

ort-circuit

.at.out

put.”

32.5.5 Distributed Database

 is.function.enables.direct.and.thus.time-saving.communication.between.slaves.using.broadcast.com-

munication

.with

out

.the.detou

.over.a.mast

er.

.In.this.case

.the.slav

.act.as.a.“pub

lisher,”

.i.e.,.the.slav

resp

onse

.does.not.go.thro

ugh

.the.coor

dinating

.mast

er,

.but.dire

ctly

.to.othe

.slav

.embed

ded

.in.the.

sequ

ence,

.the.so-c

alled

.“sub

scribers.”

. is.enab

les

.slav

.to.dire

ctly

.read.data.from.othe

.slav

.and.use.

them.as.thei

.own.inpu

. is.open

.up.the.possi

bility

.of.eci

ent

.appl

ications;

.it.also.redu

ces

.resp

onse

time

.on.the.bus.by.up.to.90%

32.5.6 Synchronization of the applications

 is.function.enables.clock.synchronous.control.in.masters.and.slaves,.irrespective.of.the.bus.load.. e.

func

tion

.enab

les

.high

.prec

ise

.posit

ioning

.proc

esses

.with.cloc

.devi

ations

.of.less.than.a.micr

osecond.

All.part

icipating

.devi

.cycl

.are.sync

hronized

.to.the.bus.mast

.cycl

.thro

ugh

.a.“glo

bal

.cont

rol”

broa

dcast

.mess

age.

.A.spec

ial

.sign.of.life.(con

secutive

.numbe

.allo

.moni

toring

.of.the.sync

hronization.

32.6 acyclic Data Exchange: MS1/MS2 relations

 e.key.feature.of.the.MS1/MS2.relation.is.the.extended.function.for.acyclic.data.communication..

 is.forms. the.requ

irement

.for.para

meterization

.and. cali

bration

.of.the.eld.devi

ces

.over.the.bus.

duri

.runt

ime

.and.for.the.intr

oduction

.of.con

rmed

.alar

.mess

ages.

.Tran

smission

.of.acyc

lic

.data.

Probus 32-11

is.executed.parallel.to.cyclic.data.communication,.but.with.lower.priority..Figure.32.3.shows.some.

sample.communication.sequences.. e.master.class.1.has.the.token.and.is.able.to.send.messages.to.

or.retrieve.them.from.slave.1,.then.slave.2,.etc.,.in.a.xed.sequence.until.it.reaches.the.last.slave.of.the.

current.list.(MS0.relation);.it.then.passes.on.the.token.to.the.master.class.2.. is.master.can.then.use.

the.remaining.available.time.of.the.programmed.cycle.to.set.up.an.acyclic.connection.to.any.slave.to.

exchange.records.(MS2.relation);.at.the.end.of.the.current.cycle.time,.it.returns.the.token.to.the.DPM1..

Similarly,.as.well.as.the.DPM2,.the.DPM1.can.also.execute.acyclic.data.exchange.with.slaves.(MS1.

relation).(Figure.32.5).

32.6.1 Variables

 e.eld-device.is.composed.of.modules.located.in.slots..Every.slot.has.now.a.set.of.variables.addressed.

with.an.index.in.the.range.of.0–255..With.the.acyclic.read.and.write.services,.it.is.possible.to.read.and.

modify.these.parameters.of.the.eld-device.. e.format.and.meaning.of.these.parameters.is.dened.in.

the.device.prole.

32.6.2 Device Model including Identication and Maintenance

For.the.uniform.identication.and.maintenance.procedures,.every.device.and.module.of.a.Probus.sys-

tem

.must.be.identied.. e.set.of.Identication.and.Maintenance.(I&M).variables.inside.every.Probus.

DP.eld-device.permits.this.functionality.. ese.variables.are.read.and.also.written.with.the.acyclic.data.

exchange.services.

32.6.3 alarm Handling

 e.alarm-handling.function.allows.a.eld-device.to.signal-detected.alarm.conditions.in.a.controlled.

procedure.to.the.DPM1.controller.. e.controller.has.to.acknowledge.the.signaled.alarms.

Possible

.alarm.conditions.are.pulled.or.plugged.modules,.diagnostic.information,.changed.parameters.

in.the.eld-device,.or.user.dened.changes.of.process.values.

Buscycle T

clock

DX(B) DX(B) DX(B) MAC1

MS1

GC = Global control (Clock; clear/operate = Status of the DPM1)

DX(B) = Data exchange (Broadcast) of the MS0 relation

MAC1 = One acyclic service of the MS1 relation

MAC2 = One acyclic service of the MS2 relation

TC = Token

ASP = Active break

PSP = Passive break

= Probus DP cycle time

= Time for the transmission of the cyclic data

MS2

MAC2 ASP PSP

… …

clear/

opera.

FIGURE 32.5 Timing.of.an.MS1/MS2.connection.with.isochronous.cycle.

32-12 Industrial Communication Systems

32.6.4 Procedure Calls

 e.procedure.call.function.allows.the.loading.of.any.size.of.data.area.into.a.eld.device.with.a.single.

comm

and.

. is.enab

les,

.for.exam

ple,

.prog

rams

.to.be.upda

ted

.or.devi

ces

.repl

aced

.with

out

.the.need.for.

manu

.loa

ding

.pro

cesses.

32.7 application Proles

Probus.stands.out.from.other.eldbus.systems.primarily.due.to.its.extraordinary.breadth.of.applica-

tion

.optio

ns.

.Tabl

.32.5.show

.all.curr

ent

.spec

ic

.Pro

bus

.appl

ication

.pro

les.

.Major.appl

ication

.pro-



les

.are.Pro

safe

.as.de

ned

.in.[IE

C84-3]

.and.Pro

bus

.PA.as.exp

lained

.in.[M0

.and.[DB

07].

references

[CMTV02].Cavalieri,.S.,.Monforte,.S.,.Tovar,.E.,.and.Vasques,.F.,.Evaluating.worst.case.response.time.in.

mono.and.mult

i-master

.pro

bus

.DP,.Four

th IEEE International Workshop on Factory Communication

Systems,

.Vas

teras,

.Swe

den,

.2002,.pp..233–240.

[DB07]

. Dietrich,. Ch,. and. Bang

emann,

. .,. Pro

bus PA, Instrumentation Technology for the Process

Industry,

.Oldenb

ourg

.Ind

ustrieverlag,

.Munich,.Germ

any,

.2007,.344.pp.,.ISBN.978-3-8356-3125-0.

[F06]

. Fels

er,

. M.,. Quali

. of. pro

bus

. insta

llations,

. Sixth IEEE

International Workshop on Factory

Communication System

. (WFCS 2006),. Confer

ence

. Center. Torin

. Incon

tra,

. Torin

. Ital

. June.

27–30,.2006.

[IEC58]

.IEC.61158,.Digita

.data.communica

tions

.for.meas

urement

.and.contr

ol—Fieldbus

.for.use. in.

indus

trial

.cont

rol

.system

.IEC,.avai

lable

.at.www

.iec.ch

[IEC84-1]

.IEC.61784-1,.IEC.61784-1:.Indu

strial

.communica

tion

.netwo

rks—Proles—Part

.1:.Fieldbu

pro

les,

.IEC,.avai

lable

.at.www

.iec.ch

TABLE 32.5 Available.Application.Proles

Designation Prole.Contents

PROFIdrive e

.pro

le

.spe

cies

.the.beh

avior

.of.devices.and.the.access.pro

cedure

.to.dat

.for.vari

able-

speed

.elec

trical

.driv

.on.Pro

bus.

.devices

.pro

le

.spe

cies

.the.cha

racteristics

.of.devices.of.pro

cess

.engin

eering

.in.pro

cess

auto

mation

.on.Pro

bus.

Robots/NC e

.pro

le

.descri

bes

.how.han

dling

.and.ass

embly

.rob

ots

.are.cont

rolled

.over.Pro

bus.

Panel

.devices

.pro

le

.descri

bes

.the.inter

facing

.of.simple.huma

.machin

.inter

face

.(HMI).devices.

tohigher.leve

.aut

omation

.comp

onents.

Encoders e

.pro

le

.descri

bes

.the.inter

facing

.of.rot

ary,

.ang

le,

.and.linea

.encoder

.wit

.single-t

urn

ormul

ti-turn

.reso

lution.

Fluid

.pow

er e

.pro

le

.descri

bes

.the.cont

rol

.of.hydra

ulic

.driv

.over.Pro

bus.

.In.coop

eration

.wit

VDMA.

SEMI e

.pro

le

.descri

bes

.cha

racteristics

.of.devices.for.semicon

ductor

.man

ufacture

.on.Pro

bus

(SEMI.sta

ndard).

Low-voltage

.swit

chgear e

.pro

le

.denes.dat

.exch

ange

.for.low-vo

ltage

.swit

chgear

.(swit

ch-disconnectors,

.mot

star

ters,

.etc.).on.Pro

bus

.DP.

osage/weighing e

.pro

le

.descri

bes

.the.implem

entation

.of.weighin

.and.dosag

.system

.on.Pro

bus

.DP.

dent

.system

s e

.pro

le

.descri

bes

.the.communic

ations

.betw

een

.devices.for.identic

ation

.purp

oses

(barcodes,.tran

sponders).

Liquid

.pumps e.prole.denes.the.implementation.of.liquid.pumps.on.Probus.DP..In.cooperation.with.

VDMA.

Remo

.I/O.for.PA.devices

Due

.to.their.spe

cial

.place.in.bus.opera

tions,

.a.dieren

.device.mode

.and.dat

.types.are.

applie

.to.the.remo

.I/Os.comp

ared

.to.the.Pro

bus

.PA.devices.

Probus 32-13

[IEC84-3].IEC.61784-3-3,.Industrial.communications.networks—Proles—Part.3-3:.Functional.safety.

eldb

uses—Additional

.sp

ecications

.fo

.CPF.3,.IEC,.ava

ilable

.at.ww

w.iec.ch

[KHU08]

.Kag

hazchi,

.H.,.Hon

gxin,

.Li,.and.Ulric

.M.,.Inuen

.of.tok

.rot

ation

.time.in.mul

.mas-

.PRO

FIBUS

.netw

orks,

.IEEE In

ternational Workshop on Factory Communication Systems,

.2008.

(WFCS 2008),.Dres

den,

.Ger

many,

.Ma

.21–23,.2008,.pp

.189–197.

[M03]

.Mit

chell,

.R.,.PRO

FIBUS: A Pocket Guide (Paperback),

. e.Ins

trumentation,

.Syst

ems,

.and.Aut

omation

Societ

.(ISA),.Res

earch

.Tr

iangle

.Pa

rk,

.NC,.Oc

tober

.2003,.200.pp

.ISB

.978-1556178627.

[P02]

.Pop

.M.,. e.new.rapid.way.to.PRO

FIBUS

.DP,.descri

bing

.PRO

FIBUS

.fro

.DP-V0.to.DP-V2,.

Pro

bus

.Orga

nization,

.No

vember

.2002,.ap

.260.pp

.Order.No:4.072.

[P2112]

.Pro

bus

.User.Organiza

tion,

.Ins

tallation

.guideline.for.PRO

FIBUS

.DP/FMS.V1.0,.Pro

bus

.User.

Organiza

tion,

.Order.at.ht

tp://www.probus.com,

.Order.No:.2.112.

[P8022]

.Pro

bus

.User.Organiza

tion,

.Han

dbook

.PRO

FIBUS

.inst

allation

.guideline.for.cab

ling

.and.ass

em-

bly

. V1.0.6,. Pro

bus

. User. Organiza

tion,

. Fre

. down

load

. at.htt

p://www.probus.com,

. Order.No:.

8.022.

[P8032]

.Pro

bus

.User. Organiza

tion,

.Han

dbook

.PRO

FIBUS

.inst

allation

.guideline.for.commis

sioning

V1.0.1,.Pr

obus

.Us

.Orga

nization,

.Fr

.dow

nload

.at.ht

tp://www.probus.com,

.Order.No:.8.032.

[V04]

.Vit

turi,

.S.,.Sto

chastic

.mode

.of.the.Pro

bus

.DP.cyc

.time

.IEE Pr

oceedings Science, Measurement

and Technology,

.151,.335–342,.Sep

tember

.4,.2004,.ISSN:.1350-2344.

[WG03]

. Weigm

ann,

. J.. and. Kili

an,

. G.,. Dec

entralization with PROFIBUS DP/DPV1: Architecture and

Fundamentals,

. Conguration and Use with SIMATIC S7,. 2003. edition,.Wiley-VCH,. Weinheim,.

Germ

any,

.Ma

rch

.1,.2004,.251.pp

.ISB

.978-3895782183.

33-1

33.1 INtErBUS Overview

INTERBUS.was.developed.by.the.German.company.Phoenix.Contact.and.presented.in.1987..INTERBUS.

has.been.desig

ned

.as.a.fast.sens

or/actuator

.bus.for.tran

smitting

.proc

ess

.data.in.indu

strial

.envi

ronments

and.is.stan

dardized

.in.the.IEC-

61158

.[1]..It.pres

ents

.seve

ral

.pecu

liarities

.that.are.main

.rela

ted

.to.

the.topo

logy

.and.to.the.prot

ocol

.that.prov

ides

.fast

.cycl

ic,

.and.time

-equidistant

.proc

ess

.data.tran

smission,

diag

nostics

.to.min

imize

.dow

ntime,

.and.eas

.ope

ration

.and.ins

tallation

.[2,

3].

.rst.impo

rtant

.feat

ure

.refe

.to.the.topol

ogy.

.INTE

RBUS

.is.a.ring.syst

em,

.that.is,.all.devi

ces

.are.

acti

vely

.inte

grated

.in.a.clos

.tran

smission

.path.(see.Figu

.33.1

. is.is.a.larg

.die

rence

.with.resp

ect

to.the.major

ity

.of.exis

ting

.eld

bus

.syst

ems,

.whic

.(acc

ording

.to.thei

.name

)

.are.base

.on.a.bus..In.a.

ring

.each.devi

.ampl

ies

.the.inco

ming

.signa

.and.forw

ards

.it,.thus.prov

iding

.a.bett

.signa

.qual

ity

whic

.in.tur

.red

uces

.the.noi

.and.ena

bles

.hig

her

.tra

nsmission

.spe

eds

.ove

.lon

ger

.dis

tances.

Unlike

.othe

.ring.syst

ems,

.the.data.forw

ard

.and.retu

.line

.in.the.INTE

RBUS

.syst

.lead.to.all.

devi

ces

.via.a.singl

.cabl

. is.mean

.that.the.gene

ral

.physi

cal

.appe

arance

.of.the.syst

.is.an.“ope

n”

.tree.

stru

cture.

.A.main.line.exit

.the.bus.mast

.and.can.be.used.to.form.seam

less

.subn

etworks

.up.to.16.leve

deep

. is.remo

ves

.one.big.limi

.of.ring

-based

.topol

ogies

.that.requ

ire

.the.comm

unication

.line.to.roun

back.to.the.star

ting

.poin

.in.orde

.to.clos

.the.ring

.With.an.open.tree.stru

cture,

.the.bus.syst

.can.be.

quic

kly

.adapt

.to.chan

ging

.appl

ications

.and.it.is.easy.to.add.new.bran

ches

.for.expa

nding

.the.syst

em.

over,

.as.com

munication

.in.the.rin

.is.uni

directional,

.it.is.wel

.sui

ted

.for.be

.opti

.tec

hnology.

.INTE

RBUS

.mast

er/slave

.syst

.enab

les

.the.conn

ection

.of.up.to.512.devi

ces,

.acro

.16.netw

ork

leve

ls.

. e.ring.is.autom

atically

.clos

.by.the.last.devi

ce.

.Coun

tless

.topol

ogies

.can.be.crea

ted.

.Bran

terminals.create.branches,.which.enable.the.connection.and.disconnection.of.devices.

.second.impo

rtant

.pecul

iarity

.is.inhe

rent

.to.the.way.node

.are.addr

essed

.and.data.are.tran

sferred

thro

ugh

.the.ring

.Unli

.in.othe

.syst

ems

.wher

.data.are.assig

ned

.by.ente

ring

.a.bus.addr

ess

.for.each.

indi

vidual

.devi

.and.it.is.tran

sferred

.thro

ugh

.dedi

cated

.fram

es,

.in.the.INTE

RBUS

.syst

.data.are.

autom

atically

.assig

ned

.to.devi

ces

.using.thei

.physi

cal

.loca

tion

.in.the.syst

.and.all.info

rmation

.for.all.

devi

ces

.are.tran

sferred

.thro

ugh

.one.total.fram

.call

.“sum

mation

.fram

e.”

. is.feat

ure

.is.prov

ided

.by.

the.physi

cal

.impl

ementation

.of.the.syst

.that.can.be.seen.as.a.long

.dist

ributed

.shi.regi

ster

.(SR).with.

seri

al/parallel

.in/o

.capa

bilities

.comp

osed

.by.seve

ral

.smal

.SRs,.each.one.belo

nging

.to.a.node

.Data.

trav

eling

.on.the.ring.are.simpl

.shi

.thro

ugh

.the.SR.cell

.and.are.dist

ributed

.thro

ugh

.the.vari

ous

devi

ces.

.With.a.suit

able

.data.orga

nization,

.at.a.spec

ic

.time.inst

ant,

.each.node.will.nd.its.rele

vant

.data.

INTERBUS

33.1. INTERBUS.Overview.....................................................................33-1

33.2

. INTE

RBUS

.Pro

tocol.......................................................................33-2

33.3

. Diag

nostics.......................................................................................33-7

33.4

. Perf

ormance

.Eva

luation.................................................................33-8

33.5

. Summ

ary...........................................................................................33-9

References.....................................................................................................33-9

Juergen Jasperneite

Ostwestfalen-

Lippe

Uni

versity

ofApp

lied

Sci

ences

Orazio Mirabella

University of Catania

33-2 Industrial Communication Systems

inside.its.local.SR.. is.plug.and.play.function.is.a.great.advantage.with.regard.to.the.installation.eort.

and.service-friendliness.of.the.system.. e.problems.and.errors,.which.may.occur.when.manually.

setting.device.addresses.during.installation.and.servicing,.are.oen.underestimated.

.order.to.provide.these.features,.various.basic.elements.must.be.used.in.the.system.as.shown.in.Figure.33.1:

Bus master:

. e.bus.master.controls.all.bus.operations..It.transfers.output.data.to.the.corresponding.

nodes,.receives.input.data,.and.monitors.data.transfer..In.addition,.diagnostic.messages.are.displayed.

and.error.messages.are.transmitted.to.the.host.system.. e.controller.has.the.responsibility.of.preparing.

the.single.total.frame.that.provides.data.distribution.among.the.various.nodes.

Remote bus:

. e.controller.board.is.connected.to.the.bus.devices.via.the.remote.bus..A.branch.from.this.

connection.is.referred.to.as.a.remote.bus.branch..Data.can.be.physically.transmitted.via.copper.cables.

(RS-485.standard),.ber.optics,.infrared.data.links,.slip.rings,.or.other.media.(e.g.,.wireless)..Special.bus.

terminal.modules.and.certain.input/output.(I/O).modules.or.devices.such.as.robots,.drives,.or.operat-

ing

.devices.can.be.used.as.remote.bus.devices..Each.one.has.a.local.voltage.supply.and.an.electrically.

isolated.outgoing.segment..In.addition.to.the.data.transmission.lines,.the.installation.remote.bus.can.

also.carry.the.voltage.supply.for.the.connected.I/O.modules.and.sensors.

Bus terminal module:

. e.bus.terminal.modules,.or.devices.with.embedded.bus.terminal.module.func-

tions,

.are.connected.to.the.remote.bus.. e.distributed.local.buses.branch.out.of.the.bus.terminal.mod-

ule

.with.I/O.modules,.which.establish.the.interface.between.INTERBUS.and.the.sensors.and.actuators..

 e.bus.terminal.module.divides.the.system.into.individual.segments,.thus.enabling.to.switch.indi-

vidual

.branches.on/o.during.operation.. e.bus.terminal.module.amplies.the.data.signal.(repeater.

function).and.electrically.isolates.the.bus.segments.

Local bus:

. e.local.bus.branches.from.the.remote.bus.via.a.bus.coupler.and.connects.the.local.bus.

devices..Branches.are.not.allowed.at.this.level.. e.communication.power.is.supplied.by.the.bus.ter-

minal

.module,.while.the.switching.voltage.for.the.outputs.is.applied.separately.at.the.output.modules..

Local.bus.devices.are.typically.I/O.modules.

33.2 INtErBUS Protocol

INTERBUS.operations.are.based.on.two.cycle.types:. e.identication.cycle.for.system.conguration.

and.error.management,.and.a.data.transfer.cycle.for.the.transmission.of.user.data..Both.cycle.types.are.

based.on.a.summation.frame.whose.structure.is.shown.in.Figure.33.2.

Controller board

Bus terminal

400 m

Remote bus

Slave nodes

20 m

12.8 km

Local bus

Master

station

FIGURE 33.1 Topology.exibility.allows.a.cost-ecient.cabling.in.machines.and.plants.

INTERBUS 33-3

 e.layer.2.summation.frame.consists.of.a.special.16.bit.loopback.word.(i.e.,.the.preamble),.the.user.

data.of.all.devices,.and.a.terminating.32.bit.frame.check.sequence.(FCS).to.control.the.data.integrity..

 e.FCS.consists.of.a.16.bit.cyclical.redundancy.check.(CRC).value.and.further.16.bits.for.controlling.

the.data.exchange.between.the.input.and.output.registers..According.to.the.physical.structure,.data.can.

be.sent.and.received.by.the.ring.structure.of.the.INTERBUS.system.in.a.single.round.(full.duplex.mode),.

and.this.results.in.very.high.protocol.eciency.

.logical.method.of.operation.of.an.INTERBUS.slave.can.be.congured.between.its.incoming.and.

outgoing.interfaces.by.the.register.set.shown.in.Figure.33.3..Each.INTERBUS.slave.is.part.of.a.large,.

distributed.SR.ring,.whose.start.and.end.point.is.the.INTERBUS.master.. e.register.set.inside.the.slave.

can.be.used.for.both.data.transfer.and.management..Data.transfer.is.performed.through.the.input.and.

output.data.registers.

During

.the.data.transfer.phase,.the.input.data.register.will.contain.input.data,.that.is,.data.that.are.to.

be.transmitted.to.the.master,.and.the.output.data.registers.will.contain.data.received.through.the.ring..

One total frame

PLC

Loopback Field n

FCS

Control

Field 1

Station 1 Station 2 Station 3 Station 4 Station n

Field 2 Field 3 Field 4

FIGURE 33.2 e.layer.2.summation.frame.structure.of.INTERBUS.

Input data register

Identication data register

Control data register

Output data register

Incoming

data ow

CRC-

Selector

Outgoing

data ow

FIGURE 33.3 Basic.model.of.an.INTERBUS.slave.node.

33-4 Industrial Communication Systems

According.to.the.logical.structure.shown.in.Figure.33.4,.the.summation.frame.will.shi.inside.all.the.

SRs.and.this.way.data.sent.by.the.master.will.cross.all.the.nodes.. ere.is.a.precise.time.instant.when.

all.output.data.registers.inside.each.slave.will.contain.the.data.addressed.to.that.slave..At.that.moment,.

data.contained.in.the.output.data.register.will.be.stored.into.the.node,.whereas.data.addressed.to.the.

master.will.be.loaded.into.the.input.data.register.and.will.begin.to.travel.along.the.ring.by.substituting.

the.original.data.into.the.summation.frame.. is.operating.mode.is.very.ecient.allowing.the.ring,.into.

a.single.round,.to.transfer.data.from.and.to.the.master.

.important.role.is.played.by.the.CRC.register,.which.is.switched.to.the.input.data.register.in.

parallel.. e.Comité.Consultatif.International.Téléphonique.et.Télégraphique.(CCITT).polynomial.

g(x).=.x

.+.x

.+.1.is.used.for.the.CRC,.which.is.able.to.detect.burst.errors.shorter.than.16.bits.. e.

CRC.registers.are.used.during.the.frame.check.sequence.to.check.whether.the.data.have.been.transmitted.

correctly..An.important.point.is.that,.since.the.CRC.is.located.at.the.end.of.the.summation.frame,.each.

slave.checks.the.data.correctness.only.when.the.whole.frame.has.crossed.inside.it,.but.as.data.contained.

into.the.summation.frame.are.changed.during.the.crossing.of.the.various.slaves,.CRC.must.be.recalculated.

several.times..For.this.reason,.two.CRC.registers.are.present.into.each.node.. e.rst.one.(on.the.le.side.

Figure.33.3).is.used.to.check.incoming.data,.whereas.the.second.one.(on.the.right.side.Figure.33.3).is.used.

to.calculate.the.new.CRC.value.to.be.attached.at.the.end.of.the.summation.frame.

.length.of.the.I/O.data.registers.in.each.node.depends.on.the.number.of.I/Os.of.the.individual.

node.. e.master.needs.to.know.which.and.how.many.devices.are.connected.to.the.bus.so.that.it.can.

assign.the.right.I/O.data.to.the.right.device..For.this.reason,.once.the.bus.system.has.been.switched.

on,.the.master.starts.a.series.of.identication.cycles,.which.enable.it.to.detect.how.many.and.which.

devices.are.connected..Each.slave.has.an.identication.data.register.with.a.xed.length.16.bit.identi-

cation

.code.

.master.can.use.this.identication.code.to.assign.a.slave.node.to.a.dened.device.class.(e.g.,.digital.

I/O.node.and.analog.I/O.node).and.detect.the.length.of.the.I/O.data.registers.in.a.data.cycle.. e.control.

data.registers.are.switched.in.parallel.to.the.identication.data.registers,.whereby.the.individual.devices.

can.be.managed.by.the.master..Commands.are.transmitted,.for.example,.for.local.resets.or.outgoing.

Out data

Data flow

inside the

shift registers

Loopback

word

Loopback

word

Master

Input

buffer

Output

buffer

N N – 1

In data

FIGURE 33.4 Logical.structure.of.the.ring.in.INTERBUS.

INTERBUS 33-5

interface.shutdown.. e.identication.cycle.is.also.used.to.nd.the.cause.of.a.transmission.error.and.to.

check.the.integrity.of.the.SR.ring.

.individual.registers.are.switched.in.the.dierent.phases.of.the.INTERBUS.protocol.via.the.selector.

in.the.ring.

.layer.1,.INTERBUS.uses.two.telegram.formats.with.start.and.stop.bits:

•

. e.5.bit.status.telegram

•

. e.13.bit.data.telegram

.status.telegram.is.used.to.synchronize.the.activities.on.the.medium.during.pauses.in.data.trans-

mission.

. e.slave.nodes.use.the.status.telegram.to.reset.their.internal.watchdogs,.which.are.used.to.

control.a.failsafe.state.. e.data.telegram.is.used.to.carry.a.byte.of.the.layer.2.payload.. e.remain-

ing

.bits.of.both.telegrams.are.used.to.distinguish.between.data.and.identication.cycles,.as.well.as.

the.data.transfer.and.FCS.phases.within.a.cycle.. is.information.is.used.by.the.selector.shown.in.

Figure.33.4.to.switch.the.relevant.register.in.the.ring..INTERBUS.uses.a.physical.transmission.speed.

of.500.kbps.or.2.Mbps.

.cycle.time,.that.is,.the.time.required.for.I/O.data.to.be.exchanged.once.with.all.the.connected.

nodes,.depends.on.the.amount.of.user.data.in.an.INTERBUS.system,.that.is,.on.the.number.of.nodes.

and.on.the.dimension.of.the.SR.inside.each.node..Depending.on.the.conguration,.INTERBUS.can.

achieve.cycle.times.of.just.a.few.milliseconds.. e.cycle.time.increases.linearly.with.the.number.of.I/O.

points,.as.it.depends.on.the.amount.of.information.to.be.transmitted..For.more.detailed.information,.

refer.to.the.chapter.performance.evaluation.

.architecture.of.the.INTERBUS.protocol.is.based.on.the.open.system.interconnection.(OSI).ref-

erence

.model.according.to.International.Standards.Organization.(ISO).7498..As.is.typical.for.eldbus.

systems,.for.reasons.of.eciency,.ISO.layers.3–6.are.not.explicitly.used.(see.Figure.33.5).but.are.com-

bined

.in.the.lower.layer.interface.(LLI).in.layer.7.. e.protocol.architecture.of.INTERBUS.provides.both.

periodic.and.asynchronous.communications.

Application process

PMS services

PNM7 services

PNM7

PNM1/2

Management

PMS

Empty (layer 3–6)

Data link layer (layer 2)

Physical layer (layer 1)

LLI

PDL

PHY

Application layer (layer 7)

FIGURE 33.5 Protocol.architecture.of.an.INTERBUS.node.