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

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KNX 42-11

42.5 Devices

Various. building. blocks. exist. for. developing. KNX. compatible. devices.. Dierent. transceivers. are.

requ

ired

.depe

nding

.on.the.tran

smission

.medi

um.

.For.TP1,.four.die

rent

.tran

sceiver

.solu

tions

.allo

optim

ization

.of.the.KNX.devi

.desig

.in.acco

rdance

.with.the.area.of.appl

ication.

.A.tran

sceiver

.circ

uit

cons

tructed

.from.disc

rete

.comp

onents

.oer

.low-

cost

.bus.acce

ss,

.but.requ

ires

.high.cert

ication

.eor

 e.use.of.the.FZE.1065.tran

sceiver

.IC.with.tran

sformer

.coup

ling

.and.bit.inte

rface

.allo

.a.high

.resis

tant

.solu

tion,

.whil

.the.FZE.1066.tran

sceiver

.with.dire

.bus.coup

ling

.enab

les

.a.resis

tant

.and.mini

atur-

ized

.solu

tion.

.Both.tran

sceiver

.ICs.oer.a.bit.inte

rface

.and.allo

.impl

ementing

.a.cert

ied

.physi

cal

.laye

with.mini

mum

.eor

.Fina

lly,

.the.TP-U

ART

.IC.is.a.tran

sceiver

.with.dire

.bus.coup

ling

.and.a.UART.

host.inte

rface.

.It.allo

.cert

ied

.and.mini

aturized

.bus.acce

.with.rela

xed

.timi

.requ

irements

.on.the.

micr

ocontroller,

.as.it.hand

les

.most.of.the.KNX.TP1.DL..For.the.PL11

.medi

um,

.only.a.singl

.type.of.

tran

sceiver

.ASIC.is.avai

lable.

. e.use.of.the.RF.and.IP.medi

.does.not.requ

ire

.hard

ware

.that.is.spec

i-

cally

.desi

gned

.for.KNX

.furt

her

.ease.syst

.deve

lopment

.and.cert

ication,

.KNX.den

.stan

dardized

.comm

unication

modu

les

.(i.e

.bus.atta

chment

.unit

.BAUs

)

.such.as.the.bus.coup

ling

.unit.(BCU

.the.bus.inte

rface

.mod-

.(BIM

.or.the.powe

rline

.inte

rface

.modu

.(PIM

.whic

.prov

ide

.an.impl

ementation

.of.the.comp

lete

netw

ork

.stac

.and.appl

ication

.envi

ronment.

. ey.can.host.simpl

.user.appl

ications,

.supp

orting

.the.use.

of.GOs.in.a.way.simil

.to.loca

.vari

ables.

.BIMs

/PIMs

.are.sold

ered

.or.deta

chable

.comm

unication

.mod-

les

.that.are.dire

ctly

.atta

ched

.to.the.main.devi

.circ

uit

.boar

.wher

eas

.BCUs.are.equi

pped

.with.housi

and.shi

elding

.aga

inst

.ele

ctromagnetic

.int

erference.

Most

.KNX.devices.come.either.in.rail-mount.housings.for.mounting.in.distribution.boxes.or.as.ush-

mount

.devi

ces.

.Flus

h-mount

.end.devi

ces

.base

.on.BCUs.are.typi

cally

.spli

.into.two.part

.the.com-

unication

.modu

.(i.e

.BCU).and.the.appl

ication

.modu

le.

.Both.are.conn

ected

.via.the.stan

dardized

physi

cal

.exte

rnal

.inte

rface

.(PEI

.whic

.can.be.con

gured

.in.a.numbe

.of.ways

.Simp

.appl

ication

.mod-

les

.such.as.wall.swit

ches

.may.use.it.for.para

llel

.digi

tal

.I/O.or.as.inpu

.to.the.BCU.A/D.conv

erter.

.More.

comp

lex

.user.appl

ications

.requ

iring

.the.use.of.a.sepa

rate

.micr

oprocessor

.may.use.the.PEI.for.high

-level

acce

.to.the.netw

ork

.stac

.via.EMI.wrap

ped

.in.an.asyn

chronous

.seri

.proto

col

.(BCU.1.devi

ces

.use.

a.proto

col

.with.prop

rietary

.hard

ware

.hand

shaking,

.whil

.the.proto

col

.supp

orted

.by.BCU.2.devi

ces

.is.

base

.on.FT1

.as.spe

cied

.in.IEC.608

70-5).

Dierent

. gene

rations

. of. TP1. comm

unication

. modu

les

. exis

. e. trad

itional

. BCU. 1,. BIM. M111

and.BIM.M115.modu

les

.feat

ure

.a.Motor

ola

.68HC

05B6

.or.comp

atible

.type.micr

ocontroller

.runn

ing

at.2.MHz.with.176.byte

.RAM,.256.byte

.EEPR

OM,

.and.5936.byte

.ROM..BCU.2.and.BIM.M113.use.a.

68HC

05BE12

.micr

ocontroller

.runn

ing

.at.2.45

.MHz.. ey.have.384.byte

.RAM,.991.byte

.EEPR

OM,

and.1190

.byte

.ROM..Most.of.the.RAM.and.ROM.are.occu

pied

.by.the.syst

.sow

are.

.To.over

come

the.seve

.perf

ormance

.limi

tations

.of.thes

.out-

dated

.plat

forms,

.a.new.gene

ration

.of.BIMs.has.been.

deve

loped.

. ey.are.base

.on.the.NEC.78K0

/Kx2

.micr

ocontroller

.and.oer.from.8.up.to.48.kB.ash.

memory..Additionally,.a.far.more.comfortable.soware.development.toolchain.(including.a.C.compiler.

and.debu

gger)

.is.avai

lable

.for.this.new.plat

form.

.For.PL11

.68HC

05B16

.micr

ocontroller

.base

.BAUs.

(e.g

.PIMs

)

.exis

.that.are.quit

.simil

.to.the.68HC

05B6

.seri

.but.feat

ure

.larg

.ROM.and.RAM.and.a.

cloc

.fre

quency

.of.4.MHz.

part

.from.thes

.stan

dardized

.BAUs

.vari

ous

.othe

.KNX.cert

ied

.inte

rface

.modu

les

.exis

.For.exam

ple,

.so-c

alled

.seri

.inte

rface

.modu

les

.(SIM

.are.avai

lable,

.whic

.can.be.dire

ctly

.sold

ered

.to.prin

ted

circ

uit

.boar

.in.a.way.simil

.to.BIMs

. ey.cont

ain

.the.comp

lete

.comm

unication

.stac

.and.the.appl

cation

.can.inte

rface

.with.the.KNX.netw

ork

.using.a.simpl

.prop

rietary

.seri

.proto

col.

.Comp

lete

.so-

are

.stac

.for.seve

ral

.micr

ocontroller

.fami

lies

.(e.g

.Atme

.ATme

.and.ARM7

.Texa

.Inst

ruments

MSP4

30,

.NEC.78K

.can.als

.be.obt

ained

.fro

.var

ious

.ven

dors.

42-12 Industrial Communication Systems

42.6 Conguration

In. KNX,. considerable. attention. is. given. to. uniform,. manufacturer-independent. conguration,.

para

meterization,

.and.bind

ing.

. is.is.refe

rred

.to.as.con

guration interworking.

.Cent

ral

.to.the.KNX.

con

guration

.inte

rworking

.conc

ept

.is.a.sing

le,

.univ

ersal

.PC.sow

are

.pack

age

.for.plan

ning

.and.com-

issioning

.KNX.inst

allations.

.It.is.main

tained

.and.sold.by.the.KNX.Asso

ciation,

.base

.on.Micr

oso

Wind

ows

.and.call

.ETS.(Eng

ineering

.Tool.Sow

are).

.ETS.assi

sts

.with.den

ing

.the.proje

.in.a.stru

tured

.way.and.is.used.to.con

gure

.the.beha

vior

.and.comm

unication

.rela

tionships

.of.KNX.devi

ces.

 is.incl

udes

.load

ing

.appl

ication

.prog

rams

.and.sett

ing

.appl

ication

.para

meters

.and.can.be.done.over.

the.netw

ork

.or.the.PEI,.if.avai

lable.

.ETS.also.prov

ides

.bus.moni

toring

.func

tions

.for.trou

bleshooting.

Manufacturers

.are.requ

ired

.to.supp

.the.nece

ssary

.devi

.and.user

-application

.desc

riptions

.alon

with.thei

.hard

ware.

.Tool

.for.thei

.crea

tion

.are.prov

ided

.by.the.KNX.Asso

ciation

.as.well

.ETS.can.also.

be.exte

nded

.by.way.of.plug

-ins,

.shou

.the.con

guration

.of.a.devi

.requ

ire

.it..Only.a.mino

.numbe

.of.

devi

ces

.need.furt

her

.setu

.tools.in.addi

tion

.to.ETS..For.inte

racting

.with.such.exte

rnal

.tools

.ETS.sup-

orts

.the.exp

ort

.of.pro

ject

.le

For

.acce

ssing

.the.con

gurable

.reso

urces

.with

.KNX.devi

ces,

.both.a.memo

ry-mapped

.appr

oach

.and.

a.more.tran

sparent

.objec

t/property-oriented

.mode

.are.den

ed.

. e.reso

urces

.them

selves

.(e.g

.memo

loca

tions,

.prop

erty

.iden

tiers,

.and.thei

.purp

ose)

.are.also.stan

dardized

.as.far.as.the.comm

unication

syst

.is.conc

erned.

. e.mana

gement procedures

.appl

icable

.for.a.part

icular

.devi

.and.its.reso

urce

.lay-

.are.spec

ied

.by.the.devi

.pro

.it.conf

orms

.to..Acce

.to.the.user.appl

ication

.stil

.larg

ely

.requ

ires

ETS.and.the.dev

ice

.man

ufacturers’

.des

criptions.

Increasingly,

.KNX.devices.that.do.not.require.ETS.for.commissioning.are.available.. is.is.referred.

to.as.E-Mo

.(for.“Eas

y”),

.whil

.con

guration

.via.ETS.is.call

.S-Mo

.(for.“Sys

tem”).

.A.vari

ety

.of.

E-Mo

des

.exis

ts.

. eir.aim.is.to.prov

ide

.inst

allers

.with.easie

.and.less.erro

r-prone

.(alb

eit

.less.powe

rful

and.exi

ble)

.ways.of.crea

ting

.comm

unication

.bind

ings.

. is.can.be.acco

mplished

.by.loca

lly

.brin

ging

the.bind

ing

.part

ners

.(and.only.them

)

.into.a.spec

ial

.con

guration

.mode.(pus

.butto

.mode

.sett

ing

tag.numbe

.on.devi

ces

.that.are.to.coop

erate

.to.iden

tical

.valu

.(LTE.mode

.or.a.hand

-held,

.dedi

cated

con

guration

.tool.that.enum

erates

.possi

ble

.bind

ing

.part

ners

.(con

troller

.mode

.Whil

.in.S-Mo

de,

.GOs.

are.boun

.indi

vidually,

.E-Mo

des

.usua

lly

.perf

orm

.bind

ing

.for.a.grou

.of.logi

cally

.corr

esponding

.GOs.

(ref

erred

.to.as.cha

nnels)

.toge

ther.

Although

.the.abil

ity

.to.be.con

gured

.with.ETS.is.a.cert

ication

.requ

irement

.for.all.KNX.devi

ces,

this.requ

irement

.is.temp

orarily

.susp

ended

.since.ETS.does.not.yet.supp

ort

.E-Mo

.devi

ces.

.A.furt

her

con

guration

.mod

.(A-

Mode)

.was.als

.par

.of.the.KNX.sta

ndard,

.but.was.rem

oved

.fro

.rel

ease

.2.0

42.7 Conclusion and Outlook

When.the.convergence.process.between.EIB,.Batibus,.and.EHS.started.in.1997,.EIB.was.assigned.

a.lead

ing

.role

.It.was.to.be.enha

nced

.by.feat

ures

.that.were.pres

ent

.in.EHS.and.Bati

bus

.but.not.yet.

in.EIB..In.2002

.a.new.stan

dard

.emer

ged

.as.a.resu

lt,

.atte

mpting

.to.brid

.thre

.die

rent

.doma

ins

by.the.comb

ination

.of.thre

.tech

nologies:

.elec

trical

.inst

allation

.(lig

hting/shading)

.via.EIB,.HVAC.

via.Bati

bus,

.and.hous

ehold

.appl

iances

.(whi

.good

.via.EHS.. is.stan

dard

.was.late

.labe

led

.KNX..

EIB.devi

ces

.were.auto

matically

.KNX.comp

liant;

.this.was.not.the.case.for.Bati

bus

.and.EHS.devi

ces,

howe

ver.

.Toda

.Bati

bus

.and.EHS.heri

tage

.has.larg

ely

.been.elim

inated

.from.KNX.sinc

.no.KNX.

prod

ucts

.base

.on. thes

.part

.of.the. stan

dard

.were.made.avai

lable

.comm

ercially.

.EHS.1.3a. has.

beco

.a.KNX-

associated

.stan

dard,

.but.the.prod

ucts

.on.the.mark

.that.are.base

.on.it.are.not.

KNX.comp

atible.

Nevertheless,

.the. KNX. stan

dard

.has. been. stea

dily

.impr

oved

.and. augm

ented.

. e.most. visi

ble

impr

ovements

.over.EIB.are.its.RF.medi

um,

.the.IP.tunn

eling

.prot

ocol,

.new.con

guration

.mode

.that.

do.not.requ

ire

.ETS,.and.the.addi

tion

.of.mete

ring

.as.well.as.full

-edged

.HVAC.cont

rol

.for.home.

as.well.as.ligh

.comm

ercial

.envi

ronments.

.Howe

ver,

.the.func

tions

.adde

.for.the.HVAC.trad

.are.

KNX 42-13

not.fully.and.seamlessly.integrated.with.those.that.have.grown.from.the.electrical.trade..As.a.con-

sequence

.fro

.the

.dev

elopments,

.the.KNX.spe

cication

.has.bec

ome

.com

plex

.to.rea

.alt

hough

con

siderable

.eo

rts

.tow

ard

.con

solidation

.wer

.tak

.for.the.cur

rent

.rel

ease

.of.the.KNX.mas

ter

.spe

ci-

cation

.(KNX

Handbook

.2.0

Nevertheless,

.the

.is.amp

.roo

.for.fur

ther

.act

ivities:

.Ope

.and.sta

ble

.for

mats

.for.the.des

cription

of.pro

duct

.con

guration

.dat

.(us

.app

lication

.res

ources)

.and.pro

ject

.spe

cic

.dat

.are.sti

.mis

sing,

alt

hough

.an.XML

-based

.pro

posal

.has.bee

.in.its.dra



.sta

.for.yea

.and.the.upc

oming

.ETS.ver

sion

4.stor

.pr

oject

.an

.pr

oduct

.da

.in.XM

.E

orts

.sh

ould

.al

.be.di

rected

.in

.a.We

.se

rvices

.ma

pping.

Whi

.pro

tocol

.sec

urity

.is.slo

wly

.bei

.add

ressed

.by.man

ufacturers,

.saf

ety

.iss

ues

.hav

.not.bee

.tak

into.ac

count

.so.fa

abbreviations

AL. Application.layer

APDU

. App

lication

.la

yer

.pr

otocol

.da

.un

. Add

ress

.ty

BAU

. Bus.at

tachment

.un

BCU

. Bus.co

upling

.un

BIM

. Bus.in

terface

.mo

dule

cEMI

. Com

mon

.ex

ternal

.me

ssage

.in

terface

. Dat

.li

.la

yer

DPT

. Dat

.po

int

.ty

EIB

. Eur

opean

.In

stallation

.Bu

EMI

. Ext

ernal

.me

ssage

.in

terface

ETS

. Eng

ineering

.too

.so

ware

. Fun

ctional

.bl

ock

FCS

. Fra

.ch

ecking

.se

quence

. Gro

.ob

ject

. Int

ernet

.pr

otocol

LTE

. Log

ical

.ta

.ex

tended

. Net

work

.la

yer

PDU

. Pro

tocol

.da

.un

PIM

. Powerline.interface.module

PL110

. Pow

erline

.11

. Rad

.fr

equency

SAP

. Ser

vice

.ac

cess

.po

int

. Tra

nsport

.la

yer

TP1

. Twi

sted

.Pa

. Tra

nsport

.la

yer

.pr

otocol

.da

.un

references

. 1.. KNX Specications, Version 2.0,.KNX.Association,.Diegem,.Belgium,.2009.

. 2.. EN.50090,.Hom

.and.buildin

.elec

tronic

.system

.(HBES),.CENELEC,.Bru

ssels,

.Belg

ium,

.1994–2009.

. 3.. EN. 133

21-1,

. Ope

. dat

. com

munication

. in. bui

lding

. aut

omation,

. con

trols

. and. bui

lding

man

agement—Home

.and.buildin

.elec

tronic

.system—P

art

.1:.Pro

duct

.and.system.req

uirements,

CEN,.Br

ussels,

.Be

lgium,

.2006.

. 4.. EN. 133

21-2,

. Ope

. dat

. com

munication

. in. bui

lding

. aut

omation,

. con

trols

. and. bui

lding

man

agement—Home

.and.buildin

.elec

tronic

.system

s—Part

.2:.KNXnet/IP.communic

ation,

.CEN,.

Bru

ssels,

.Be

lgium,

.2006.

42-14 Industrial Communication Systems

. 5.. ISO/IEC.14543-3,.Information.technology—Home.electronic.system.(HES).architecture—Part.3,.

ISO/IEC,.Gen

eva,

.Sw

itzerland,

.2006–2007.

. 6.. Han

dbook for Home and Building Control, Basic Principles,

.5th. edn.,. ZVEI/ZVEH. (eds.),. KNX.

Ass

ociation,

.Diegem,.Be

lgium,

.2006.

. 7.. W..Kas

tner

.and.G..Neugsc

hwandtner,

.EIB:.Euro

pean

.Ins

tallation

.Bus,.in.Ind

ustrial Communication

Technology Handbook,

.CRC.Pr

ess,

.Bo

.Ra

ton,

.FL,.2005.

. 8.. ERC.reco

mmendation

.70-03.rel

ating

.to.the.use.of.sho

.rang

.devices.(SRD),.CEPT,.Euro

pean

Comm

unications

.Oce,.Co

penhagen,

.Denm

ark,

.1997–2010.

. 9.. EN. 13757,. Comm

unication

. system

. for. meter

. and. remo

. readin

. of. meter

. CEN,. Bru

ssels,

Belg

ium,

.2002–2008.

. 10.. EN. 50065-1,. Spe

cication

.for.signa

lling

.on.low-vo

ltage

.elec

trical

.inst

allations

.in.the. fre

quency

rang

.3.kHz.to.148.5.kHz..Genera

.req

uirements,

.fre

quency

.ban

.and.elec

tromagnetic

.dist

ur-

bances,

.CENELEC,.Br

ussels,

.Be

lgium,

.2001.

. 11.. EN.50523,.Ho

usehold

.ap

pliances

.int

erworking,

.CENELEC,.Br

ussels,

.Be

lgium,

.2009.

. 12.. IEC.60870-5-1,.Tele

control

.equi

pment

.and.system

.Par

.5:.Tran

smission

.pro

tocols—Section

.1:.

Tran

smission

.fra

.fo

rmats,

.IEC,.Gen

eva,

.Sw

itzerland,

.1990.

. 13.. IEC.60870-5-2,. Tele

control

.equi

pment

.and.system

.Par

.5:.Tran

smission

.pro

tocols—Section

.2:.

Link.tra

nsmission

.pr

ocedures,

.IEC,.Gen

eva,

.Sw

itzerland,

.1992.

43-1

43.1 Introduction

Time-triggered.systems.derive.control.by.the.progression.of.time.and.thus.use.the.concept.of.time.in.

the.prob

lem

.stat

ement

.as.well.as.in.the.prov

ided

.solu

tion.

. is.appr

oach

.supp

orts

.a.spec

ication

.of.

inte

rfaces

.incl

uding

.the.temp

oral

.doma

.(e.g

.send.and.rece

ive

.inst

ants

.of.mess

ages)

.and.the.impl

mentation

.of.“tem

poral

.rew

alls,”

.whic

.prev

ent

.erro

.prop

agation

.via.cont

rol

.signa

ls.

.Time

-triggered

syst

ems

.sup

port

.memb

ership

.ide

ntication,

.int

eroperability,

.and.rep

lica

.det

erminism.

.conc

epts

.of.time

-triggered

.syst

ems

.have.been.comp

osed

.in.the.time

-triggered architecture

.[KB0

3],

esta

blishing

.a.fram

ework

.for.the.impl

ementation

.of.depe

ndable

.dist

ributed

.real

-time

.embed

ded

.appl

cations.

.Besid

.proto

cols

.that.empl

.a.time

-triggered

.sche

duling

.like.Flex

ray

.[Fle

05]

.and.TT-C

[HMF

H00],

.ther

.exis

.thre

.proto

cols

.that.are.espe

cially

.desig

ned

.acco

rding

.to.the.time

-triggered

arch

itecture:

.time

-triggered

.proto

col

.(TTP

.time

-triggered

.Ether

net

.(TTEt

hernet),

.and.TTP.for.SAE.

Clas

.A.[SA

E95a]

.app

lications

.(TT

P/A).

. TTP. (als

. know

. as. TTP/

. proto

col

. since. it. suit

. SAE. clas

. C. appl

ication

. requ

irements

[SAE9

5b])

.prov

ides

.a.high

.depe

ndable

.real

-time

.comm

unication

.serv

ice

.with.a.faul

t-tolerant

.cloc

sync

hronization

.and.membe

rship

.serv

ice.

.TTP.is.suit

able

.for.X-by-

wire

.syst

ems

.in.the.autom

otive

.and.

avio

nics

.dom

ain.

Protocols of the

Time-Triggered

Architecture: TTP,

TTEthernet, TTP/A

43.1. Introduction.....................................................................................43-1

43.2

. e.Tim

e-Triggered

.Par

adigm......................................................43-2

Sparse.Time. •. Flow.Control.and.Temporal.Firewall

43.3. Time-Triggered.Communication..................................................43-3

43.4

. Time

-Triggered

.Pro

tocol

.(TT

P)....................................................43-4

Fault.Hypothesis.and.Fault.Handling. •. Fault.Tolerance. •. .

Membership

43.5. Time-Triggered.Ethernet................................................................43-5

Principles.of.Operation. •. Time.Format. •. Periods. •. Fault-Tolerant.

TTEthernet.Conguration. •. Clock.Synchronization

43.6. TTP/A................................................................................................43-7

Interface.File.System. •. e. ree.Interfaces.of.a.Smart.

Transducer. •. Principles.of.Operation

Acknowledgments.....................................................................................43-11

References...................................................................................................43-11

Wilfried Elmenreich

University of Klagenfurt

Christian

El-Salloum

Vienna University

of Tec

hnology

43-2 Industrial Communication Systems

TTEthernet. is. a. uniform. communication. architecture. covering. a.whole. spectrum. of. distributed.

applications.reaching.from.simple.non-real-time.applications.to.multimedia.systems.up.to.the.most.

demanding.safety-critical.hard.real-time.products.

.time-triggered.eldbus.TTP/A.is.intended.for.the.integration.of.smart.transducers.in.all.types.

of.distributed.real-time.control.systems..Although.the.rst.targets.are.automotive.applications,.TTP/A.

has.been.designed.to.meet.the.requirements.of.process.control.systems.as.well..TTP/A.supports.low-cost.

implementations.on.a.wide.set.of.available.component-o-the-shelf.microcontrollers.

.this.chapter,.we.introduce.these.protocols.by.rst.giving.a.short.overview.on.the.common.under-

lying

.concepts.of. the.time-triggered.architecture..A. reader. that.is.familiar. with.the. time-triggered.

paradigm.may.directly.go.to.the.sections.on.TTP,.TTEthernet.and.TTP/A,.where.we.introduce.the.

application.domains,.requirements,.and.principles.of.operation.of.the.specic.protocols.

43.2 the time-triggered Paradigm

 e.time-triggered.paradigm.encompasses.a.set.of.concepts.and.principles.that.support.the.design.

of.highly.dependable.hard.real-time.systems.

43.2.1 Sparse time

When.global.physical.time.is.used.to.deduce.causality.of.distributed.events,.it.is.necessary.to.synchro-

nize

.the.local.clocks.precisely..Clock.synchronization.is.concerned.with.bringing.the.time.of.clocks.in.a.

distributed.network.into.close.relation.with.respect.to.each.other..Measures.of.the.quality.of.clock.syn-

chronization

.are.precision.and.accuracy..Precision.is.dened.as.the.maximum.oset.between.any.two.

clocks.in.the.network.during.an.interval.of.interest..Accuracy.is.dened.as.the.maximum.oset.between.

any.clock.and.an.absolute.reference.time.

Due

.to.the.impossibility.to.perfectly.synchronize.clocks.and.the.digitalization.error,.it.is.impossible.

to.guarantee.that.two.observations.of.the.same.event.will.yield.the.same.timestamp..A.solution.to.this.

problem.is.provided.by.introducing.the.concept.of.a.sparse time base.[Kop92]..In.this.model,.the.timeline.

is.partitioned.into.an.innite.sequence.of.alternating.intervals.of.activity.and.silence..Figure.43.1.depicts.

the.intervals.of.silence.(s).and.activity.(a).. e.duration.of.the.silence.intervals.depends.on.the.precision.

of.the.clock.synchronization.

.architecture.must.ensure.that.signicant.events,.such.as.the.sending.of.a.message.or.the.obser-

vation

.of.an.event,.occur.only.during.an.interval.of.activity..Events.occurring.during.the.same.seg-

ment

.of.activity.are.considered.to.have.happened.at.the.same.time..Events.that.are.separated.by.at.least.

one.segment.of.silence.can.be.consistently.assigned.to.dierent.timestamps.for.all.clocks.in.the.system.

43.2.2 Flow Control and temporal Firewall

In.order.to.transfer.data.between.two.components,.they.must.agree.on.the.ow-control.mechanism.to.

use.and.the.direction.of.the.transfer..Commonly,.a.communication.between.two.subsystems.is.either.

controlled.by.the.sender’s.request.(push.style).or.by.the.receiver’s.request.(pull.style).[AFI+00].

Figure

.43.2.shows.the.push.method.. e.producer.is.allowed.to.generate.and.send.its.message.at.any.

time,.thus.ow.control.is.managed.by.the.producer.. is.method.is.very.comfortable.for.the.push.pro-

ducer,

.but.the.push.consumer.has.to.be.watchful.for.incoming.data.messages.at.any.time,.which.may.

s s

a a

Real time

FIGURE 43.1 Sparse.time.base.

Protocols of the Time-Triggered Architecture: TTP, TTEthernet, TTP/A 43-3

result.in.high.resource.costs.and.dicult.scheduling.[EHK01]..Popular.“push”.mechanisms.are.mes-

sages,

.interrupts,.or.writing.to.a.le.[DeL99].. e.push.style.communication.is.the.basic.mechanism.of.

event-triggered.systems.

.Figure.43.3,.the.ow.control.is.on.the.consumer..Whenever.the.consumer.asks.to.access.the.mes-

sage

.information,.the.producer.has.to.respond.on.the.request.. is.facilitates.the.task.for.the.pull.con-

sumer,

.but.the.pull.producer.has.now.to.be.watchful.for.incoming.data.requests.[EHK01]..Popular.“pull”.

mechanisms.are.reading.a.le,.polling,.state.messages,.or.shared.variables.[DeL99].. e.pull-style.com-

munication

.is.the.basic.mechanism.of.client-server.systems.. e.time-triggered.paradigm.implements.a.

hybrid.approach,.which.is.explained.in.Figure.43.4.

.temporal.rewall.[KN97].enables.dierent.control.ow.directions.between.sender.and.receiver.

(Figure.43.4).

.model.uses.a.combination.of.“push”.and.“pull”.communication..Each.component.possesses.

a.memory.object.that.acts.as.a.data.source.and.sink.for.communication.activities..Components.that.

want.to.submit.data.are.able.to.write.the.data.into.this.memory.using.a.producer’s push.interface.. e.

transmission.of.data.between.the.sender.and.the.receiver.is.handled.autonomously.by.the.communica-

tion

.subsystem.according.to.the.time-triggered.paradigm..Aer.transmission,.the.consumer.component.

accesses.the.data.using.a.consumer’s pull.interface.

.values.in.the.memory.are.state.messages.that.keep.their.content.until.they.are.updated.and.overwritten..

Since.in.the.time-triggered.architecture.all.nodes.have.knowledge.about.transmission.schedules.and.access.to.

a.global.time.base,.the.instant.when.the.protocol.updates.a.value.in.the.memory.element.is.known.to.all.nodes.

43.3 time-triggered Communication

 e.very.basic.principle.of.time-triggered.communication.is.that.the.events.of.message.transmission.

depend.only.on.the.progression.of.time.and.not.on.the.availability.of.new.information.. erefore,.time-

triggered

.communication.requires.a.sucient.synchronization.among.all.nodes’.clocks.

Sender

Receiver

Control

ow

Data

ow

FIGURE 43.2 Push.communication.model.(implicit.ow.control).

Sender Receiver

Control

flow

Data

flow

FIGURE 43.3 Pull.communication.model.(explicit.ow.control).

Control

ow

Control

ow

Sender

Memory

Data

ow

Receiver

Memory

Data

ow

Time-triggered

communication system

Information push

ideal for sender

Information pull

ideal for sender

FIGURE 43.4 Temporal.rewall.

43-4 Industrial Communication Systems

 e.instants.at.which.information.is.delivered.or.received.are.a.priori.dened.and.known.by.all.nodes.

of.a.cluster..Any.node-local.scheduling.strategy.that.will.satisfy.the.known.deadlines.is.“t.for.purpose.”.

It.is.the.responsibility.of.the.time-triggered.communication.service.to.transport.the.information.from.

the.temporal.rewall.of.the.sending.node.to.the.temporal.rewall.of.the.receiving.node.within.the.inter-

val

.delimited.by.these.a.priori.known.fetch.and.delivery.instants.

43.4 time-triggered Protocol (ttP)

 e.TTP.[TTA03].is.a.fault-tolerant.protocol.providing

•

. Autonomous.fault-tolerant.message.transport.at.known.times.and.with.minimal.jitter.between.

the.nodes.of.a.cluster.by.employing.a.time.division.multiple.access.(TDMA).strategy.on.replicated.

communication.channels

•

. Fault-tolerant.clock.synchronization.that.establishes.a.global.time.base.without.relying.on.a.cen-

tral

.time.server

•

. A.membership.service.to.inform.every.correct.node.about.the.consistency.of.data.transmission..

 is.service.can.be.viewed.as.a.distributed.acknowledgment.service.that.informs.the.application.

promptly.if.an.error.in.the.communication.system.has.occurred

•

. Clique.avoidance.[BP00].to.detect.faults.outside.the.fault.hypothesis,.which.cannot.be.tolerated.

at.the.protocol.level

.TTP,.communication.is.organized.into.TDMA.rounds.as.depicted.in.Figure.43.5..A.TDMA.round.

is.divided.into.slots..Each.node.in.the.communication.system.has.its.sending.slot.and.must.send.

frames.in.every.round.. e.frame.size.allocated.to.a.node.can.vary.from.2.to.240.bytes.in.length,.each.

frame.usually.carrying.several.messages.. e.cluster.cycle.is.a.recurring.sequence.of.TDMA.rounds;.

in.dierent.rounds.dierent.messages.can.be.transmitted.in.the.frames,.but.in.each.cluster.cycle.the.

complete.set.of.state.messages.is.repeated.. e.data.are.protected.by.a.24.bit.cyclic.redundancy.check.

(CRC).. e.schedule.is.stored.in.the.message.descriptor.list.(MEDL).within.the.communication.con-

troller

.of.each.node.

.clock.synchronization.is.necessary.to.provide.all.nodes.with.an.equivalent.time.concept..In.doing.

so,.it.makes.use.of.the.common.knowledge.of.the.send.schedule..Each.node.measures.the.dierence.

between.the.a.priori.known.expected.and.the.observed.arrival.time.of.a.correct.message.to.learn.about.

the.dierence.between.the.sender’s.clock.and.the.receiver’s.clock..A.fault-tolerant.average.algorithm.

needs.this.information.to.periodically.calculate.a.correction.term.for.the.local.clock,.so.that.the.clock.is.

kept.in.synchrony.with.all.other.clocks.of.the.cluster.. e.membership.service.uses.a.distributed.agree-

ment

.algorithm.to.determine.whether,.in.case.of.a.failure,.the.outgoing.link.of.the.sender.or.the.incom-

ing

.link.of.the.receiver.has.failed.

.core.algorithms.of.TTP.have.been.formally.veried.to.prove.their.correctness..Particular.control-

ler

.hardware.has.been.tested.with.multimillion.fault.injection.and.heavy.ion.radiation.experiments.and.

experiments.with.electromagnetic.interferences.have.been.carried.out.successfully.

Node A

m1,m2,m3 m1,m6,m8

m1,m6,m8

m1,m2

m1,m2,m4

m1,m5,m6

m1,m5,m6m1,m2,m3

Channel A

Channel B

TDMA round

Cluster cycle

Time

Node A Node A Node AOther slots Other slots Other slots Other slots

FIGURE 43.5 Frames,.messages,.slots,.TDMA.round,.and.cluster.cycle.in.TTP.communication.

Protocols of the Time-Triggered Architecture: TTP, TTEthernet, TTP/A 43-5

43.4.1 Fault Hypothesis and Fault Handling

Provided.that.the.components.of.a.properly.congured.TTP-based.system.are.in.dierent.fault.contain-

ment

.regi

ons,

.each.can.fail.in.an.arbi

trary

.way..Unde

.this.assu

mption,

.the.prob

ability

.of.two.conc

ur-

rent

.inde

pendent

.comp

onent

.fail

ures

.is.smal

.enou

.to.be.consi

dered

.a.rare.even

.that.can.be.hand

led

by.an.app

ropriate

.nev

er-give-up

.(NG

.str

ategy

.[TT

A03,

.p..27]

.for.hard

ware

.faul

ts,

.TTP.is.desig

ned

.to.isol

ate

.and.toler

ate

.singl

e-node

.faul

ts.

.By.intr

oducing

.a.

bus.guar

dian,

.it.is.guar

anteed

.that.a.faul

.node.cann

.prev

ent

.corr

ect

.node

.from.exch

anging

.data

 e.bus.guar

dian

.ensu

res

.that.a.node.can.only.send.once.in.a.TDMA.roun

.ther

eby

.elim

inating

.the.

prob

lem

.of.bab

bling

.idi

ots

.tha

.mon

opolize

.the.com

munication

.med

ium.

43.4.2 Fault tolerance

 e.mechanisms.described.above.ensure.fault.tolerance.at.the.communication.subsystem.level.in.TTP..

 ese.mech

anisms

.of.the.comm

unication

.subs

ystem

.guar

antee

.that.faul

.node

.cann

.prev

ent

.cor-

ect

.node

.from.comm

unicating

.and.serv

.as.a.comm

unication

.plat

form

.for.the.appl

ication.

.At.the.

appl

ication

.leve

.faul

.toler

ance

.need

.to.be.impl

emented

.by.a.faul

t-tolerance

.laye

.and.an.appr

opriate

appl

ication

.desig

.Faul

.toler

ance

.can.be.real

ized

.by.repl

icating

.a.sow

are

.subs

ystem

.on.two.fail-

silent

node

.Tole

rance

.of.a.singl

.arbi

trary node failure

.can.be.ensu

red

.by.trip

.modu

lar

.redu

ndancy

.(TMR

)

voti

ng.

.Both.mech

anisms

.will.toler

ate

.singl

e-component

.faul

.with.the.resp

ective

.fail

ure

.sema

ntics

and.are.thu

.t.to.han

dle

.bot

.tra

nsient

.and.per

manent

.har

dware

.fau

lts.

43.4.3 Membership

A.major.objective.in.the.design.of.TTP.is.that.the.protocol.should.transmit.data.consistently.to.all.cor-

rect

.node

.of.the.dist

ributed

.syst

.and.that

.in.case.of.a.fail

ure,

.the.comm

unication

.syst

.shou

deci

.on.its.own.whic

.node.is.faul

ty.

. ese.prop

erties

.are.achi

eved

.by.the.membe

rship

.proto

col

.and.

an.ack

nowledgment

.mec

hanism.

Each

.node.of.a.TTP-b

ased

.clus

ter

.main

tains

.a.membe

rship

.list.with.all.node

.that.are.consi

dered

to.be.corr

ect.

. is.info

rmation

.is.upda

ted

.loca

lly

.in.acco

rdance

.with.succ

essful

.(or.unsu

ccessful)

.data.

tran

smissions

.and.thus.ree

cts

.the.loca

.view.of.the.rece

iving

.node.on.all.othe

.node

.With.each.tran

mission,

.each.rece

iver

.sees.and.chec

.the.send

er’s

.membe

rship

.that.is.incl

uded

.in.the.send

er’s

.tran

mission

.or.hid

den

.in.the.CRC.cal

culation.

.inco

nsistent

.view.on.the.membe

rship

.can.only.be.caus

.by.faul

.exce

eding

.the.faul

.hypo

thesis

(e.g

.mult

iple

.conc

urrent

.faul

.due.to.heav

.elec

tromagnetic

.inte

rference).

.In.this.case

.a.cliq

.avoi

ance

.mech

anism

.esta

blishes

.consi

stency

.by.rest

arting

.the.node

.whic

.have.inco

nsistent

.view.with.the.

major

ity

.of.nod

es.

43.5 time-triggered Ethernet

TTEthernet.is.a.uniform.communication.architecture.covering.the.whole.spectrum.of.real-time.appli-

cations

.[KAG

S05].

.It.meet

.the.requ

irements

.of.simpl

.non-

real-time

.appl

ications,

.mult

imedia

.syst

ems,

and.safe

ty-critical

.hard.real

-time

.syst

ems.

.TTEth

ernet

.is.full

.back

ward-compatible

.with.the.Ether

net

stan

dard

.and.comb

ines

.the.pro

perties

.of.sta

ndard

.Ethe

rnet

.and.TTP

.impo

rtant

.feat

ure

.of.TTEth

ernet

.is.that.it.enab

les

.the.inte

gration

.of.nonc

ritical

.best

-eort

.appl

cations

.and.high

.dema

nding

.safe

ty-critical

.cont

rol

.appl

ications

.into.a.singl

.netw

ork.

.Due.to. its.

back

ward

.comp

atibility

.to.the.Ether

net

.stan

dard,

.exis

ting

.Ether

net-based

.lega

.appl

ications

.can.be.

inte

grated

.into.a.TTEth

ernet

.netw

ork

.with

out

.any.modi

cation.

.It.is.guar

anteed

.by.desig

.that.thes

lega

.appl

ications

.cann

.disru

.the.temp

orally

.pred

ictable

.comm

unication

.of.hard.real

-time

.appl

ica-

tions

.in.the.TTEt

hernet

.net

work.

43-6 Industrial Communication Systems

43.5.1 Principles of Operation

In.order.to.allow.deterministic.real-time.communication.to.coexist.with.competing.senders.com-

municating

.in.a.bes

t-eort

.man

ner,

.TTE

thernet

.dis

tinguishes

.bet

ween

.two.fun

damentally

.di

erent

cat

egories

.of.tra

c:

.sta

ndard event-triggered

.(ET

)

.Eth

ernet trac

.and.tim

e-triggered

.(TT).Eth

ernet

trac.

.In.the.cas

.of.TTE

thernet

.tra

c,

.the.sen

ders

.are.coo

perating

.acc

ording

.to.a.con

sistent

.mes

sage

.sch

edule

.in. a.way. tha

.no. con

icts

.wil

.occ

.bet

ween

.TTE

thernet

.mes

sages

.in. a.fau

lt-free

TTE

thernet

. sys

tem.

. TTE

thernet

. tra

c

. pro

vides

. dep

endable

. har

. rea

l-time

. com

munication

. tra

c

.whi

.coe

xists

.wit

.sta

ndard

.Eth

ernet

.tra

c

.but.is.gua

ranteed

.not.to.be.dis

rupted

.by.sta

ndard

Eth

ernet

.mes

sages.

Since

.sta

ndard

.Ethe

rnet

.tra

c

.typ

ically

.ori

ginates

.in.an.unc

ontrollable

.ope

.wor

ld,

.no.tem

poral

gua

rantees

. for. the. sta

ndard

. Ethe

rnet

. tra

c

. can. be. giv

en.

. Whe

never

. a. sta

ndard

. Ethe

rnet

. mes

sage

(wh

ich

.is.typ

ically

.unc

oordinated)

.con

icts

.wit

.a.TTEt

hernet

.mes

sage,

.the.tra

nsmission

.of.the.sta

dard

.Ethe

rnet

.mes

sage

.wil

.be.pre

empted

.in.ord

.to.be.abl

.to.tra

nsmit

.the.TTEt

hernet

.mes

sage

.wit

an.a.pri

ori

.est

ablished

.con

stant

.del

.(i.

e.,

.thi

.del

.is.the.sam

.in.the.cas

.whe

.a.sta

ndard

.Ethe

rnet

mes

sage

.has.to.be.pre

empted

.in.ord

.to.res

olve

.a.con

ict

.as.it.is.in.the.cas

.whe

.no.con

ict

.has.

occ

urred).

.Whe

.the.tra

nsmission

.of.the.TTEt

hernet

.mes

sage

.has.bee

.com

pleted,

.the.pre

empted

.sta

dard

.Eth

ernet

.me

ssage

.wi

.be.au

tomatically

.re

transmitted.

. pre

emption

. of. sta

ndard

. Eth

ernet

. mes

sages

. is. per

formed

. by. a. ded

icated

. TTE

thernet switch

[SG

AK06].

. e.swi

tch

.han

dles

.the.sta

ndard

.Eth

ernet

.tra

c

.acc

ording

.to.the.sto

re-and-forward

.par

adigm

.and.a.bes

t-eort

.del

.acc

ording

.to.the.sta

ndard

.Eth

ernet

.spe

cication.

. e.tim

e-triggered

trac.is.handled.according.to.the.cut-through.paradigm.with.an.a.priori.known.constant.delay.and.

min

imal

.jit

ter.

43.5.2 time Format

A.digital.time.format.can.be.characterized.by.three.parameters:.the.granularity,.the.horizon,.and.

the.epo

ch.

. e.gra

nularity

.det

ermines

.the.min

imum

.int

erval

.bet

ween

.two.adj

acent

.tic

.of.a.clo

ck,

tha

.is,.the.sma

llest

.int

erval

.tha

.can.be.mea

sured

.wit

.thi

.tim

.for

mat.

. e.rea

sonable

.gra

nular-

ity

.can.be.der

ived

.fro

.the.ach

ieved

.pre

cision

.of.the.clo

.syn

chronization

.[KO

87].

. e.hor

izon

det

ermines

.the.ins

tant

.whe

.the.tim

.wil

.wra

.aro

und.

. e.epo

.det

ermines

.the.ins

tant

.whe

.the.

mea

suring

.of.tim

.sta

rts.

.tim

.for

mat

.of.TTEt

hernet

.is.a.bin

ary

.tim

.for

mat,

.whi

.is.bas

.on.the.phy

sical

.sec

ond

.rep

resented

.by.64.bit

. e.fra

ctions

.of.a.sec

ond

.are.rep

resented

.as.24.neg

ative

.pow

ers

.of.2,.whi

.res

ults

in.a.gra

nularity

.of.abo

.60.ns,.and.the.ful

.sec

onds

.are.rep

resented

.as.40.posi

tive

.pow

ers

.of.2.whi

res

ults

.in.a.hor

izon

.abo

.30,

000

.yea

rs.

. e.tim

.for

mat

.has.bee

.sta

ndardized

.by.the.OMG.in.the.sma

tra

nsducer

.int

erface

.sta

ndard

.[OM

G02].

. e.rep

resentation

.of.the.bin

ary

.tim

.for

mat

.can.be.tra

nslated

to.th

.wa

.cl

ock

.ti

.by.a.st

andard

.Gr

egorian

.ca

lendar

.fu

nction.

43.5.3 Periods

In.TTEthernet,.the.period.durations.of.time-triggered.messages.are.restricted.to.the.positive.and.nega-

tive

.pow

ers

.of.2.of.the.sec

ond

.(1.s,.2.s,.4.s.….or.1/2.s,.1/4.s,.1/8.s.…)..Due.to.thi

.res

triction,

.eac

.per

iod

dur

ation

.can.be.rep

resented

.by.one.of.the.64.bit

.of.the.bin

ary

.tim

.for

mat.

. e.bit.rep

resenting

.the.

per

iod

.dur

ation

.of.a.tim

e-triggered

.mes

sage

.is.cal

led

.the.per

iod bit.

. e.TTEt

hernet

.imp

lementation

(ve

rsion

.1.9

)

.sup

ports

.16.di

erent

.dur

ations

.and.thu

.req

uires

.4.bit

.to.enc

ode

.the.per

iod

.bit.(se

.Fig

ure

43.

6).

. e.os

.of.the.sen

.ins

tant

.of.a.mes

sage

.to.the.sta

.of.the.per

iod

.is.cal

led

.the.pha

.of.the.mes

sage.

. e.pha

.is.rep

resented

.by.a.pat

tern

.of.12.bit

.rig

.to.the.per

iod

.bit

. us

.in.TTEt

hernet

.2.byt

are.req

uired

.to.stor

.the.per

iod

.dur

ation

.and.the.pha

.of.a.mes

sage.

. es

.2.byt

.are.cal

led

.the.per

iod

identier.