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ALLENBRADLEYCONTROLLOGIXAND

COMPACTLOGIXPLCAPPNOTEFORVIPER

SYSTEM

PN0095008325

Revision0

ReleasedNovember2011

TECHNICALSERVICESUPPORTBULLETIN


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CalAmpWirelessNetworksTechnicalSupport|Tel507.833.8819|[email protected] Page2of10

CONTENTS

1. Overview.........................................................................................................................................................................3

2. AllenBradleyCompactLogix/ControlLogixPLCs.............................................................................................................3

2.1.

PLCladder

logic

on

restart

opens

all

connections

at

once

instead

of

sequentially

...................................................

3

2.2. ABCompactLogix/ControllogixseriesPLCsEtherNet/IPconnectiontimeout...........................................................4

2.3. ABCompactLogix/ControllogixseriesPLCssendstomanyCIPForwardOpenandCIPForwardClose..............6

2.4. ABCompactLogix/ControlLogixseriesPLCssendsmanyTCP/IPkeepalivemessages...............................................9

3. Viper.............................................................................................................................................................................10

3.1. SetupViperinroutermode(insteadofBridgemode).............................................................................................10

3.2. FilteringTCPkeepalivewithViperTCPproxymode................................................................................................10

3.3. ReplacingorresettingaViperusingproxymodewithoutrestartingpolling...........................................................10


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1. OVERVIEW

AguidetoassistwithAllenBradleyCompactLogix/ControlLogixcommunicationsetupbetweenmasterPLCandremotePLC

usingABEtherNet/IPTCPprotocolbetweenPLCs.

PLCcommunication

via

serial

lines

or

serial

terminal

server

is

not

covered

here,

never

the

less

some

of

the

information

couldapply.

NOTE:PleaseconsulttheCalAmpsViperGeneralPLCsetupsupportbulletinforimportantinformationonsettingup

systemswithPLCs.

2. ALLENBRADLEYCOMPACTLOGIX/CONTROLLOGIX PLCS

BelowisalistofimportantsettingstoimprovecommunicationwhenusedwithalimitedbandwidthVipernetwork.More

informationoncommunicationcanbefoundintheCalAmpsViperGeneralPLCsetupsupportbulletinonCalAmps

supportWebpage.

NOTE:Whenrequired,contactyourPLCproviderorAllenBradley/RockwellAutomationsupport.

2.1. PLC LADDER LOGICON RESTART OPENS ALL CONNECTIONS ATONCEINSTEAD OF

SEQUENTIALLY

WhenPLCladderprogramissetuptohaveatstartupallwritemessagerungssettotrue,allTCPconnectionsaretriggered

"simultaneously".ThiscreatesanoverloadofTCPSYNsandsomewhatcouldcongesttheonairtrafficdependingonthe

system.

Itisrecommendedtosetuptheladderwritemessagerungsnottostartupsimultaneously.Writemessagesshouldbesetup

toopentheTCPconnectionsequentially.FormoreinformationcontactyourPLCproviderorAllenBradley/Rockwell

Automationsupport.


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2.2. AB COMPACTLOGIX/CONTROLLOGIX SERIES PLCSETHERNET/IP CONNECTION TIMEOUT

(SETTING TIMEOUT TO SHORTCANCAUSEPROBLEMS!)

WhenusingtheEthernet/IPwithAllenBradleyCompactLogix/ControlLogix(Logixseries),theTCPConnectiontimeoutisset

onapermessageinstructionbasisusingMessageConfigurationratherthanChannelconfiguration Channel1ofthe

MicroLogixseries.

WhenmessagesaredefinedusingMessageConfigurationandusingpathex:LocalENB,2,192.168.1.9:1,0.

Briefdescription:

TCPconnectionisopenedwhenthefirstmessageissent.

TheTCPconnectiontimeoutissetbydefaultto120secsincetheinactivitydefaultsettingis120sec.

WhileconnectionisestablishedwithsameremoteIPandsameport,ex:192.168.1.9, othermessageswilluse

thesameTCPconnection,andthereforeresettingthetimeoutcountforeachmessagesent.

Whenallmessagesareusingthesamedefaultinactivitytime(120sec)theTCPconnectionsstaysopenaslong

thenextmessageissentwithintheinactivitytimeoutperiod.

TheTCPconnectionisclosedafterthelastmessageplustheinactivityperiod(default120sec).

The

TCP

connection

can

also

be

terminated

based

on

network

connection

problems.

Exampleusingdefaultinactivitytimeout(120sec).

OverwritingthedefaultinactivitytimeoutfortheTCPconnectioninMessageConfiguration:

(Notrecommendedunlessrequired)

ItispossibletooverwritetheMessageConfigurationdefaultinactivitytimeoutvaluebyusingpathex:LocalENB,2,

192.168.1.9:inactivity100,1,0.Usinginactivity100wouldsettheinactivitytimeoutto100secondsinsteadofthedefault

120seconds.(Note:Settingofinactivityx:wherexcanbebetween1and120seconds,usingx>120secondswilldisable

themessagecompletely).

Overwritingthedefaultinactivitytimeoutisnormallynotrequiredandcancauseadditionalsideeffects.Oneoftheseside

effectswouldbewhentheinactivitytimeoutislessthanthelongestdelaybetweentwomessages;additionalIPmessages


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aresentforeachcloseandreopenoftheTCPconnection.Thisaddsalotofonairtrafficandimpactsthesystem

performance.

NotewhenusingdifferentinactivitytimeoutvaluesformessageswiththesameTCPconnection:

WhendifferentmessagesforthesameremotesharethesameTCPconnection,eachdifferentmessagesinactivitytimeout

wouldrestartthetimeouttimer.Messageexample:msg1inactivity60,msg2inactivity100,msg3inactivity30.These

messagesare

then

sent

as

follows:

msg1

is

sent,

msg2

is

sent,

msg3

and

then

await

is

done.

Since

the

last

message

was

msg3withinactivitytimeoutof30seconds,theTCPconnectionwouldcloseafter30secondsofmsg3.

Settingexampleusingcustominactivitytimeout(100sec).

Summary

on

TCP

connection

timeout

(inactivity

setting)

SincethelongestinactivitytimeoutperTCPconnectionwitharemoteunit(PLC/RTU)is120seconds(basedonmessage

inactivitymaxof120seconds), itisimportantthateachremote(PLC/RTU)ispolledwiththe120secondperiodtoavoid

extratrafficresultingfromadditionalTCP/IPopenandcloseconnectionmessages.Forsystemswherepollingisdone

infrequently(>120sec)theadditionalTCPtrafficneedstobeconsideredforthesystemtrafficplan.

FornormaloperationtheinactivitytimeoutdoesnotneedtobespecifiedinthePathsetting.Masterandremotesshould

besetthisway,especiallyifremotePLCssendunsolicitedmessagesorinitiatecommunicationwithotherremotes.Ifa

systemhasamixofPLCs(CompactLogix/ControlLogixwithMicroLogix/SLC),thenalsorefertoCalAmpsAllenBradleyPLC

forViperSystemsupportbulletinavailableonCalAmpsWEBsiteundersupport.


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2.3. AB COMPACTLOGIX/CONTROLLOGIX SERIES PLCSSENDS TO MANYCIPFORWARDOPEN

AN D CIPFORWARDCLOSE

WhenusingtheEtherNet/IPwithCIPcommunicationprotocolwithAllenBradleyCompactLogix/ControlLogixPLCs(and

withotherLogixseriesPLCs),theoptiontouseConnectedorUnconnectedisavailableintheMessageConfiguration.

BydefaulttheConnectedcheckboxisselectedandthereforeitwilladdadditionalmessages(CIPforwardopenandCIP

forward

close

messages)

for

each

read

/

write

operation

when

next

message

is

sent

outside

the

message

timeout

period

(default=30sec).

Tolowertheonairtrafficthe"Connected"checkboxshouldbeunchecked(Unconnected).

ConnectedorUnconnectedoperationdescriptionforCIP:

Whenthe"Connected"checkboxischecked(Connected),ifthere'snotaCIPconnectionalreadyestablished,then

thecontrollersendsanopenforwardCIPconnectioncommandandwaitsforthegoodresponsepriorto

transmittingthereadorwritecommand. TheCIPconnectionremainsopenaslongasthereisactivitypriortothe

timeout(default=30sec). AnymessageinstructionsendingcommandstothesamedevicecanusethesameCIP

andTCPconnection. Ifthistimeoutisreached,acloseCIPconnectioncommandissent.

Whenthe"Connected"checkboxisunchecked(Unconnected),thecontrollerusestheUnconnectedCIPserviceto

transmitthereadorwritecommand,sothereislessoverhead.

TheConnectiontimeoutisonapermessageinstructionbasisasshownbelow thisiswithregardstotheCIP

ConnectiononlynottheTCPconnection,whichisonlycontrolledbytheInactivityTimeout:

For the Logix controllers, theUnconnectedTimeout has to be individually adjusted in each message

instruction tag. The default is 30,000,000 microseconds (30 seconds):


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Whenusing

Message

type

EtherNet/IP

CIP

protocol.

TolowertheonairtrafficuncheckConnectedintheMessageConfigurationmethod.

BelowisanexamplewhentheMessageTypeis"CIPDataTableRead"or"CIPDataTableWrite". Notethatthe

"Connected"checkboxshouldbeunchecked,thisis becauseifyouleaveitchecked,theneverytimetheMSGinstructionis

executedaCIPconnection(withCIPopenmessage)willbeestablishedandbroken(withCIPclosemessage) whichadds

unnecessarilytothenetworktraffic.

Whencommunication

between

ControlLogix/CompactLogix

and

other

Logix

series

PLCs.

ThesePLCs/ControllerusuallyuseEtherNet/IPCIPunconnectedprotocoltocommunicatebetweeneachother.

Note(seebelow)thatwhentheMessageTypeis"SLCTypedRead"or"SLCTypedWrite",theLogixMSGinstructionalways

usesanUnconnectedCIP(noticethatthe"Connected"checkboxisuncheckedandgrayedout).Forexamplethisisused

whenusingPCCCencapsulatedinEtherNet/IPcommand.OthersthanreadorwriteforSLCtypesarenotdescribedinthis

document.


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SummaryofConnectedorUnconnectedoperation

WithConnectedoptionselectedandpollingintervalbetweenMessagesforthesameremoteCIPconnectionislonger

thantheUnconnectedTimeout(default30seconds),CIPForwardOpenandCIPForwardClosemessagesadd4extra

onairmessages(includesmsgreply)foreachunitpolled.Ifeachpollis2messages(msgandreply)the4extramessages

increasethemessageload(onair)by200%.

Therefore"Connected"checkboxshouldbeunchecked(Unconnected)toavoidsending)CIPForwardOpenandCIP

ForwardClosemessages.IfConnectedisrequiredthenincreasetheUnconnectedTimeoutandConnectionRate

timeoutto

avalue

greater

than

the

polling

interval

per

remote

(use

precaution

with

this).

TimeoutsusedformessageresponsesoverEtherNet/IPConnectedorUnconnectedshouldnotbetooshort,therefore

shouldnotbesetlowerthan15sec(normally)intheeventitisrequiredbeinglowerthan30sec forapplicationlevel

retransmission.TheTCP/IPcommunicationdriverdoesitsownretransmissionsandwillnotrequireapplication

retransmissionsofmessagessinceaTCPconnectionwillnotlooseamessageunlesstheconnectionterminatesnormallyor

duetoaproblem. ThereforewithTCPlongertimeoutswithinreasonareok.Longertimeouts(ex30sec)areoksincethey


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minimizeduplicatedmessagebeingbufferedbyTCPintheeventofnetworkcongestionorcommunicationproblemswith

remoteunit.

WithfuturereleasesofPLCsoftware/firmwarethedescribedoperationcouldchange.Itisalwaysrecommendedtobe

informedonPLCreleasechangesfromyourPLCproviderorAllenBradley/RockwellAutomationsupport.

2.4. AB COMPACTLOGIX/CONTROLLOGIX SERIES PLCSSENDS MANYTCP/IPKEEPALIVE

MESSAGES

TheCompactLogix/ControlLogixseriesPLCssendsTCP/IPkeepalivemessagesevery8secondsinbothdirectionsforeach

TCPconnection.WhenseveralPLCsdothesameitispossiblethatagoodpartoftheonairbandwidthisusedupbythe

keepalivetraffic.

WerecommendthattheViperisconfiguredinroutermodeandthatTCPproxyisenabled.TheViperTCPproxyfeaturewill

filterouttheTCP/IPkeepalivemessages.

ThePLCsTCPkeepalivecannotbedisablednoradjusted.RecommendedtoAllenBradley/RockwellAutomationtohavean

optioninthePLCsettingstodisablekeepaliveandhavingusersettablekeepaliveintervals.Thiscouldpotentiallybecome

availableinfuturereleasesofPLCfirmware.


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3. VIPER

3.1. SETUP VIPERINROUTER MODE (INSTEAD OF BRIDGEMODE)

Info:ViperBridgemodecannotfilterkeepaliveandcannotoperateinTCPproxymode.

IfthesystemhasveryfewunitsandfewmessagesViperBridgemodecouldbeused.ButforlargersystemsandPLCdoing

manykeepalives,oronairnetworkbeingcontentious,itmayberequiredtouseroutermode.Routermodeallows

retransmissionofmessageslostduetoonaircontention.Bridgemodeonlydoesbroadcastswithoutretries.InBridge

modetheapplicationneedstoretrylostmessages.

3.2. FILTERINGTC P KEEPALIVE WITHVIPERTCP PROXYMODE

WhenusingTCPprotocolandhavingPLCswheretheTCPkeepaliveratecannotbecontrolled,itisimportanttoenable

ViperTCP(OIPproxy)mode.ThisrequiresthatallVipersareconfiguredinroutermode(ViperBridgemodecannotfilter

keepaliveandcannotoperateinTCPproxymode).

Note:ForPLCswherethekeepalivecanbecontrolledandarerequired,setkeepaliveto4minutes.

OneoftheViper'sTCPproxymodeusagesallowsfilteringofkeepalivemessagesandpreventsthemtobesentovertheair.

Withoutthisfiltering,severalPLCssendingkeepalivemessagescouldeasilyloadtheonairnetwork.

SeeViperusermanualandWebpagestoenableproxy.BydefaultViperproxymodeisenabled.SeeViperWebpage

Advancedsetup >OIPoptimizations.AlsounderNetworkmanagement >NeighborTables(neighbormanagement)make

surethatneighborsareconfiguredwiththeproxyattribute.

3.3. REPLACINGOR RESETTING A VIPERUSINGPROXYMODEWITHOUT RESTARTING POLLING

Whenreplacingorresetting:aremoteViper,aViperusedasarepeater,orevenamasterViperconnectedthrougha

switch,theViperproxycontextislostandwilloperatewithouttheproxybenefit.

ToreestablishTCPproxycontextfortheTCPconnection,thePLCneedstoclosetheoldTCPconnectionandreopenanew

TCPconnection.ThereforenormallyafterdoingVipermaintenancethemasterPLCneedstoberestarted.FutureViper

firmwaremayreestablishproxyautomatically.

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