OPENENVIRONMENTFOR PROGRAMMINGSMALL CONTROLLERS ACCORDING
TO IEC 61131-3STANDARD
DARIUSZ RZOCA, JANSADOLEWSKI, ANDRZEJ STEC, ZBIGNIEW WIDER, BARTOSZ TRYBUS, AND
LESZEK TRYBUS
∗
Abstrat. AontrolengineeringenvironmentalledCPDevforprogrammingsmallontrollersinST,FBDandILlanguages
ofIEC61131-3standardispresented.Theenvironmentonsistsofaompiler,simulatorandhardwareongurer. Itisopeninthe
sensethat: (1)odegeneratedbytheompileranbeexeutedbydierentproessors,(2)low-levelomponentsoftheontroller
runtimeprogramaredevelopedbyhardwaredesigners,(3)ontrolprogrammersandenelibrarieswithfuntions,funtionbloks
andprograms.
OfthethreeIEClanguages,STStruturedTextisabasisforCPDev. FBDdiagramsaretranslatedtoST.ILompileruses
thesameodegenerator. Theruntimeprogramhas theformofvirtualmahinewhihexeutesuniversal odegenerated bythe
ompiler.ThemahineisanANSICprogramwithsomeplatform-dependentomponents.ThemahinesforAVR,ARM,MCS51
andx86proessorshavebeendevelopedsofar. AppliationsinludetwoontrollersforsmallDCSsystemsandPCequippedwith
I/Oboards. CPDevmaybedownloadedfromhttp://pdev.prz-rzeszow .pl /dem o.
Keywords: ontrolengineeringtool,IEC61131-3standard,STlanguageompiler,multi-platformvirtualproessor
1. Introdution. Remarkablenumberofsmall-and-medium-saleompaniesinEuropemanufature
tran-smitters, atuators, drives, PID and PLC ontrollers, and other ontrol-and-measurement equipment.
Engi-neering tools for programming suh devies are often fairly simple and do not orrespond to IEC 61131-3
standard[4℄, requiredbygrowingnumberofustomers. Theproblem maybesolvedto someextentby
devel-opingopenengineering environmentsforprogrammingsmallontrol deviesbasedonAVR, ARM,MCS51or
othermiroontrollersaordingtoIEC languages(61131-3will bedroppedforbrevity). Developmentofsuh
environmentalledCPDev(Control ProgramDeveloper)wasinitiatedbytheauthorsattheendof2006.
TheCPDevisopenin thefollowingsense:
•
odegeneratedbytheompileranbeexeutedbydierentproessors,•
low-levelomponentsofruntimeprogramareprovidedbyhardwaredesigners,•
ontrolprogrammersreatetheirownlibrarieswithreusableprogramunits.TheCPDevompilergeneratesanintermediate,universalodeexeutedbyruntimeinterpreterattheontroller
side. Dierent proessorsrequiredierentinterpreters. This resembles somewhatthe oneptof Javavirtual
mahines[7℄apableofexeutingprogramsondierentplatforms. HenetheinterpretersoftheCPDevuniversal
odearealsoalledvirtual mahines.
Thesameapproahwasadaptedearlierin ISaGRAFpakagefromISC Triplex[5℄ (nowinRokwell).
IS-aGRAFuniversalodeisalledTIC(TargetIndependent Code) andmaybeexeutedonplatformssupporting
Windows, Linux, VxWorks, QNX and RTX. Muh simplerCPDev does notimpose suh requirements,
how-ever. AnotheropenenvironmentalledBeremiz[11℄ompilesIEC languageodeintoC/C++program,tobe
translatedfurtherintoproessorode. InthisaseommerialrestritionsontheuseofC/C++ompilersmay
mattersometimes.
This paper follows a few earlier publiations, e.g. [9, 10℄, whih reported on CPDev development. The
ontentisorganizedasfollows. ForthereadernotfamiliarwithIECstandard,Se.2providessomeinformation
on programming in high-level ST language. Components of CPDev, user interfae, standard funtions and
librarieswithfuntionbloksaredesribedinSe.3. Setion4haraterizessanner,parserandodegenerator
ofSTompiler, writtenin C#at Ms.NET platform. Someinstrutionsof theuniversalodealledVMASM
(Virtual Mahine Assembler) are also presented. Setion 5 desribes operation and struture of the virtual
mahine. The mahine is written in industry standard C and onsists of universal and platform-dependent
modules. Platform-dependentmodulesarewrittenbyhardwaredesigners. Setion6haraterizesdevelopment
of userfuntion bloks, both in ST andC languages. Bloks written in Cbeome omponents of thevirtual
mahine. Programming in graphial FBD and textual ILlanguages is desribed in Se. 7. FBD diagram is
translatedtoSTandthenompiled. AppliationsofCPDevforprogrammingasmallontrol-and-measurement
∗
Departmentof ComputerandControlEngineering, Faultyof Eletrialand ComputerEngineering, RzeszowUniversityof
distributed system, ontrollers of ship ontrol-and-positioning system and a softontroller based on PC with
I/OboardsarepresentedinSe.8.
2. A few notes on IEC 61131-3. The IEC 61131-3 standard[4℄ denes veprogramming languages,
LD,IL,FBD,STandSFC,allowingtheuserto hoosetheonesuitableforpartiularappliation. Instrution
list IL and Strutured Text ST are text languages, whereas Ladder Diagram LD, Funtion Blok Diagram
FBD and Sequential Funtion Chart SFC are graphial ones (SFC is not an independent language, sine it
requires omponents written in the other languages). Relatively simple languages LD and IL are used for
small appliations. FBD, ST and SFC are appropriate for medium-sale and large appliations. John and
Tiegelkamp'sbook[6℄isagoodsouretolearnIEC programming.
STisahigh-levellanguageoriginatedfromPasal,espeiallysuitableforompliatedalgorithms. Equivalent
odeforaprogramwritteninanyoftheotherfourlanguagesanbedevelopedinST,butnotvieversa. Hene
mostofengineeringpakagesuseSTas adefaultlanguageforprogramminguserfuntionbloks. Due tosuh
reasons,SThasbeenseletedasabaselanguagefortheCPDevenvironment.
2.1. Datatypes. Datatypes,literals(onstants)andvariablesareommonomponentsofIEClanguages.
Names (identiers) are typial, although there is no distintion between apital and small haraters. The
standarddenestwentyelementarydata types, severalof whih arelistedin Table2.1together withmemory
sizes andranges(inCPDev). BOOL,INT,REALand TIMEaremostommon. FALSE,13,-4.1415and T#1m25s
areexamplesoforrespondingonstants.
Table2.1
SeveralelementaryIECdatatypes
Type Size(range) Type Size(range)
BOOL 1B(
0
,1
) LREAL 8BIEEE-754formatBYTE 1B(
0
...255
)TIME
4B(-T#24d20h31m23s648ms...
WORD 2B(
0
...65535
) T#24d20h31m23s647ms)INT 2B(
−
32768
...32767
)TIME_OF_DAY
4B(
00
:00
:00
.
00
...REAL 4BIEEE-754format
23
:59
:59
.
99
)Thestandarddenesthree levelsforaessing variables,LOCAL,GLOBALandACCESS.LOCALsareavailable
in theprogram,funtion blokor funtion. GLOBALs anbeusedin thewholeprojet,butprograms,funtion
bloksorfuntionsmustdelarethemasEXTERNAL.ACCESSvariablesexhangedatabetweendierentsystems.
2.2. POU units. Programs, funtion bloks and funtions, alled jointly Program Organization Units
(POUs), are omponents of IEC projets. Funtion bloks, designed for reuse in dierent parts of program,
are of ruial importane. A blok involvesinputs, outputs and memory for data from previous exeutions.
Therefore the bloks must be delared as instanes. The IEC denes small set of standard bloks, suh as
ip-ops,edgedetetors,timersandounters. Threeofthem areshowninFig.2.1.
Fig.2.1. Examplesofstandardfuntionbloks: RSip-op,R_TRIGrisingedgedetetor,TONon-delaytimer
2.3. Programming. ProgramswritteninSTorotherlanguagesbeginwithdelarationsofvariablesand
instanesoffuntionbloksplaedbetweenVAR_EXTERNALorVARandEND_VARkeywords. GLOBALvariablesare
delared before programs orseparately. Thedelarations are followed by list of statements. Thestatements
involveexpressionswhih,whenevaluated,yieldresultsinoneofdeneddatatypes,i.e. elementary(Table2.1)
STlanguageprovidesvetypesofstatements:
•
assignment:=(Pasalsymbol),•
seletionsIF,CASE,•
loopsFOR,WHILE,REPEAT,•
earlyexitsRETURN,EXIT,•
funtionandfuntion blokinvoations.Simpleexamplesarepresentedinthefollowingsetions. Typialprogramlookslikeasequeneoffuntionand
funtionblokinvoations(alls).
3. CPDev environment. The CPDevonsists of threeprograms exeuted by PC andoneby the
on-troller(Fig3.1). ThePCprogramsareasfollows:
•
CPDevompilerofSTlanguage,•
CPSimsimulator,•
CPConongurerofhardwareresoures.Theprogramshavedediated interfaesand exhangedata throughlesin appropriate formats. The CPDev
ompiler(thesamenameasthepakage)generatesuniversalodeexeutedbyvirtualmahine(VM)runbythe
ontroller. TheVMoperatesasaninterpreter. TheuniversalodeisalistofinstrutionsofVMlanguagealled
VMASMassembler. VMASMis notrelated toanypartiular proessor,but loseto typialassemblers. The
ompileremploysSTsyntaxrules,listofVMASMinstrutionsandPOUsfromlibraries. Besidestheuniversal
odetheompilergeneratessomeinformationfordebuggingandsimulationbyCPSim.
Fig.3.1. ComponentsofCPDevenvironment
CongurationofhardwareresouresbymeansofCPConinvolvesmemory,input/outputandommuniation
interfaes. Userspeiationsdene memorytypesandsizes, numbersand typesofI/Osandommuniation
hannels, validity ags, et. Alloation of hardware resoures has the form of a map that assigns symboli
addressesfromSTprogramstophysialones. Byusingit,theompiledodeanbeassembledforapartiular
platformto reatenal, universalexeutableode. FromCPDevviewpoint,hardwareplatformsdieronlyin
hardwarealloationmaps, whereastheompiledodeis idential.
TheCPDev environmenthasbeenreentlyextended by graphieditor of FBDdiagrams andompiler of
ILlanguage. FBD diagramis automatiallyonverted intoST ode andompiled asabove. Compilersof ST
andILdierin detailsonly.
3.1. User interfae. MainwindowofCPDev STompilerisshownin Fig.3.2. The windowonsists of
threeareas:
•
treeofprojetstruture,ontheleft,•
programinSTlanguage,enter,•
messagelist,bottom.Framesoftheareasanbeadjusted andtheontentssrolled.
TreeoftheSTART_STOPprojetshowninthegureinludesPOUunitwiththeprogramPRG_START_STOP,
ve global variables from START to PUMP, task TSK_START_STOP, and two standard funtion bloks TON and
TOFfrom IEC_61131library. The programis written aordingto ST languagerules. Therstpartinvolves
delarations VAR_EXTERNAL of the use of global variables. Loal delarations of the instanes ON_DELAYand
OFF_DELAYofthebloksTON,TOFaretheseondpart. Programbodyonsistsoffourstatements. Therstone
turnsaMOTORonifSTARTispressed,providedthat STOPorALARMarenot. NextthreestatementsturnaPUMP
onandoveseondsafter theMOTOR(FBD diagramorrespondingtothis projetisshowninFig 7.1).
Globalvariablesandthetaskaredenedusingseparatewindows(notshown). AordingtoIECstandard
the variables anbe assigned CONSTANT and RETAINattributes, and logialaddresses. Task anbe exeuted
one, ylially with agiven period, orassoon aspreviousexeution is ompleted. There is no limiton the
numberofprogramsassignedtoatask.
Fig.3.2.UserinterfaeofSTompiler(START_STOPprojet)
arenomistakes,theompiledprojetis storedin twoles. Therstoneontainsuniversalexeutableodein
binaryformatforthevirtualmahine. Theseondonestoresmnemoni ode,togetherwithsomeinformation
forsimulatorandhardwareongurer(variablenames,et.).
3.2. Funtionsandfuntionbloks. TheCPDevompilerprovidesmostofstandardfuntionsdened
inIEC. Fivegroupsofthemfollowedbyexamplesarelistedbelow:
•
typeonversions: INT_TO_REAL,TIME_TO_DINT,TRUNC,•
numerialfuntions: ADD,SUB,MUL,DIV,SQRT,ABS,LN,•
Booleanand bitshiftfuntions: AND,OR,NOT,SHL,ROR,•
seletionandomparisonfuntions: SEL,MAX,LIMIT,MUX,GE,EQ,LT,•
funtionsoftimedatatypes: ADD,SUB,MUL,DIV(IECusesthesamenamesasfornumerialfuntions).SeletorSEL,limiter LIMITand multiplexerMUXfrom seletionandomparision grouparepartiularly useful.
Variablesofanynumerialtype,i. e.INT,DINT,REALandLREALareargumentsinmostofrelevantfuntions.
Twolibrariesoffuntionblokareavailable,namely:
•
Basi_blokslibrarywithsimpleblokssupplementingthestandard.Therstone involves: (1) ip-opsandsemaphoreRS,SR, SEMA,(2) risingandfalling edgedetetorsR_TRIG,
F_TRIG, (3) up, down, up-down ounters CTU, CTD, CTUD, (4) pulse, on-delay, o-delay timers TP, TON, TOF.
Blokstypialforsmallmultifuntionontrollersareintheseondlibrary,i.e. integrator,lters,max/minover
time,memories,timemeasurement,et.
4. STlanguageompiler. ThetaskoftheompileristoonvertXMLsourelewiththeprojetinST
languageintoalewithuniversalodeinbinaryformat. Generaldiagramoftheompileroperationinvolving
sanner,parserandodegeneratorisshownin Fig.4.1.
Fig.4.1. STompileromponents
4.1. Sanner, parser and ode generator. The sanner (lexial analyser) analysesharater stream
from STsourele anddeomposesit into lexialunits,i. e. tokens. Thetokensarelassiedinto ategories
suh as identiers, keywords,operators, onstants(a few ategories), delimiters, diretives, omments, white
spaesandinvalidharaters. Thetokenswithategoriesareolletedonalistpassedtotheparser.
The parser operates aording to top-down sheme with syntax direted translation [3℄. By employing
theST syntaxthe parser reognizesonseutivetoken onstrutionsfrom thesanner list. White spaesand
omments are dropped. When orretonstrution isreognized the parser replaesitby aset of mnemoni
instrutionsoftheVMASMassembler. Todoso,theparseremploysbuiltinelementarydatatypes(Table2.1)
andlistofVMASMinstrutions. ExamplesoftheseinstrutionsarepresentedinTable4.1.
Table4.1
ExamplesofVMASMassemblerinstrutions
Instrution Meaning Instrution Meaning
MCD Constantinitialization GE Greaterorequal
MEMCP Assignment SHL Bitshifttotheleft
ADD Addition JMP Unonditionaljump
SUB Subtration JZ Conditionaljump
AND Logiprodut MEMCP Memoryopy
NOT Negation RETURN Returnfromfuntion
NormallyasingleSTstatementistranslatedintoseveralVMASMinstrutions. Sometranslationsrequire
introdutionofauxiliaryvariablesandlabels. DeriveddatatypesandPOUsfromlibraries(funtions,funtion
bloksandprograms)arealsoparsed. Themnemoniodeiswritteninaspeialtextformat. Theodeanbe
onsolidatedwithothermnemoni odes.
In the third step the ode generator onverts the onsolidated mnemoni ode into universal exeutable
odein binaryformat. MnemonisoftheVMASMinstrutions,namesofthevariablesandlabelsarereplaed
by orresponding number identiers. To do so, the generator employs a Library Conguration File (LCF)
withtheidentiersof theinstrutions,numbersand typesoftheoperands,andinformationhowtheoperands
are aquired (operand identier may be an index to variable or a diret value). Eah implementation of
virtual mahine is dened by spei LCF onguration le. Besides binary le with the exeutable ode
theompilergeneratesatext lewithmnemoni ode,someadditionalinformation forCPSimsimulatorand
CPConongurer(variablenames,et.) andompilationreport(HTML).
4.2. Parser and ode generatorlasses. Essentialomponentsoftheompileraredesignedaslasses
in C#language[1,2℄. Eah tokenof STlanguageisenapsulated into anobjetoforresponding lass. The
lassesinheritfromanabstratSTIdentifiatorlass. Duringompilation,identiersareolletedintolists.
Identiers in alist are heked for uniqueness. When idential namesare found ompilation is stopped and
errorreported. Ifloalidentierhidesaglobalone,theompilerproduesawarning.
The parser generates text sequene of VMASM instrutions for the ode generator. Eah instrution is
represented by a mnemoni followed by operand names. Code generator replaes mnemonis and variable
nameswith appropriatenumberidentiers (indexes). Whileproessingan instrution,the generatorextrats
some information from libraries, e.g. operand size, type and passing method. The number identier an
be interpreted as a pointer to variable or as immediate value. Instrutions resulting from ompilation are
representedby instanes of VMInstrutionlass. Theoperand listVMOperand is also storedasa member of
thislass. Byusinglistsofoperandstypialproblemswithxed-sizeoperandtablesareavoided.
5. Multi-platformvirtual mahine. Binary lewiththeuniversalode andhardwarealloationmap
from the CPCon ongurer are downloaded into the ontroller, to be proessed by virtual mahine. Main
featuresoftheproessingareharaterizedbelow.
a)OperationofVM b)Memoryorganization
Fig.5.1. VirtualMahine
5.1. Operation yle. Virtualmahine isan automatonoperatingaordingto Fig.5.1a. Asindiated
before, the mahine is spei for a partiular proessorand works as an interpreter. The task onsists of
programsexeutedonseutively. Thebinaryodeinvolvesnumberidentiersoftheinstrutionsandaddresses
of operands. The mahine, similarly as a real proessor, maintains program ounter with the addressof
in-strution to be exeuted, and base addressof the data area with operands(speied for eah POU). Given
theinstrution address,the mahine fethes theidentier, deodesit, fethes theoperands,and exeutesthe
instrution. Stak emulationand update of the base addresses permit multiple, onurrentalls of funtions
and funtion bloks. The mahine monitorstime yle ofthe task andsets alarmag if timeoutappears. It
alsotriggersinput/outputproedures responsibleforexternalvariables.
Alloationofsoftwaretomemorysegmentsisshownin Fig.5.1b. Theinstrutionsandtheiroperandsare
in the ode segment (read only). Data segmentontainsglobal, loal and auxiliaryvariables, someof them
withonstantvalues. Thedata segmentanbeaesseddiretly orindiretlybyspeialvirtualregisters. The
mahine's internal memory keepsode of the interpreter, staks and registers. There is no wayof aessing
internalmemoryfromtheprogramlevel. Themahineisableto exeutemultiple instanesofprograms.
As shown in Fig.5.2, thevirtual mahine onsistsof afew universal andplatform-dependentmodules to
simplify implementation. The universalmodules remainunhanged(if one negletsompilation of thesoure
ode for agiven proessor). The platform-dependent modules interfae the mahine to partiular hardware,
exeutingVMrequeststolow-levelproedures. Forinstane,themodule Time&Clokisassoiatedwith
hard-ware,asitemploystimeinterruptstohandleTIMEdata. DATE_AND_TIMEdatarequirereal-timelok(RTC)on
board. I/Ofuntionsprovideinterfaetoanalogandbinaryinputsandoutputs,andtoommuniationeldbus
Fig.5.2. Universalandplatform-dependentVMsoftwaremodules
The universal part of the virtual mahine hasbeen written in ANSI C, so it an be diretly applied to
dierent proessors. As indiated in Se. 4.1, the number of data types and the way in whih the mahine
instrutions are exeuted are dened by the LCF onguration le. Forexample, one anlimit the number
ofelementarydatatypesor deneasubset ofVMASM instrutionto beused. Aset of generalspeiations
has been developed in CPDev for handling proessor omponents (interrupt system, RTC) and external
in-terfaes(I/O,ommuniations). Thespeiationsare in theform ofprototypesof orrespondingproedures
(names, types of inputs and returned outputs). The prototypes do not depend on proessor and hardware
solutions.
Thelewith theprototypesisompiled togetherwiththeuniversalmodules ofthevirtualmahine. The
ontents(bodies)ofthe speiationproeduresanbepreparedbyhardwaredesignersand, asabinaryle,
onsolidatedwiththeompileduniversalmodules. Thisgivestheompleteodeofthevirtualmahineforgiven
platform. Tillnow,themahinesforAVR,ARM,MCS-51andPCplatformshavebeendeveloped.
We stress that the ontentsof low-level proedures dependent on hardware solutionsmay bewritten by
designersthemselves. ThismakestheCPDevpakageopen inthehardwaresense.
6. User dened funtion bloks. The CPDev environment allowsthe user to dene funtion bloks
bothatPCsideandatontrollerside,i. e. asomponentsofvirtualmahine. ThePCsidebloksarewritten
in ST, whereas theVM side ones are in C. However,the C bloks are still invokedin themain ST program
ompiledanddownloadedfrom PC.So, asfaras invoationsareonerned, thereis nodierene betweenST
andCbloks.
6.1. ST bloks. User libraries are reated in CPDev as typial projets whih may inlude all kinds
of POU units of IEC standard, i. e. programs, funtions and funtion bloks. Delarations VAR_INPUTand
VAR_OUTPUTdetermineinput/outputstrutureoffuntionsandfuntion bloks. Thereisnodierenebetween
programming of a projet diretly for ontroller implementation and programming a library. However, the
libraryprojetissemi-ompiledto VMASMmnemonisand notto binaryform. Sothelast omponentof ST
ompiler,odegenerator(Fig. 4.1),is notneeded. Thele withmnemonis beomesuser-dened libraryand
isexportedtoLibrariesfolder.
Example of user funtion blok FB_PULSE is shown in Fig.6.1. The blok generatessingle pulse at the
outputQaftertimeT,sinerisingedgehasappearedattheinputIN.Theprogramoftheblokmayimplement
FBDdiagramofFig.6.1b,withstandardbloksR_TRIG,RSandTONfromCPDevIEC_61131library(Fig.2.1).
CorrespondingST odeis shownin Fig.6.1,with FB_PULSEbelonging totheprojetPROJ_MY_BLOCK(top of
Fig.6.1). XMLlewithPROJ_MY_BLOCKSsoureodeshouldbesavedforfutureextensionsandmodiations.
Semi-ompilationoftheprojetyields ale withVMASMmnemonis, alled,forinstane, My_Library. This
lemust beexported toLibraries. IfFB_PULSEis needed ina newprojet, bothMy_Libraryand IEC_61131
mustbeimported (thelattertosupporttheformer).
6.2. C-language bloks. Suh bloks are needed at hardware level to handle I/Oand ommuniation
hannels. Inputs andoutputsaredelaredin ST, buttheblokbodyisimplementedin C,atvirtualmahine
side(delarations are also repeated). Diretive (*$HARDWARE_BODY_CALL...*)informsCPDev ompilerthat
theblokisaomponentofVM.
Table6.1presentsinitialpartsoftheodeofGPS_GGAblokwhihprovidesserialommuniationwithaGPS
devieaordingtoNMEAprotool(GGAisaommandinNMEA).IdentierID:0003inthe(*$HARDWARE...)
a)Timediagram
) STode
b)FBDrealization
Fig.6.1. FuntionblokFB_PULSE
Table6.1
Delaration ofClanguageblokforGPSinterfaing
STdelaration CdelarationinVM
FUNCTION_BLOCK GPS_GGA typedef strut
(*$HARDWARE_BODY_CALL __delspe(align(4))
ID:0003; Align:4 *) tagIO_GPS_GGA
VAR_INPUT {
PORT : BYTE; END_VAR /*inputs*/ VM_BYTE Port;
VAR_OUTPUT /*outputs*/
UTC : TIME_OF_DAY; VM_TIME_OF_DAY Ut;
LAT : LREAL; VM_LREAL Lat;
LON : LREAL; VM_LREAL Lon;
ALT : LREAL; VM_LREAL Alt;
QUALITY : BYTE; END_VAR VM_BYTE Quality;
END_FUNCTION_BLOCK } IO_GPS_GGA, *PIO_GPS_GGA;
Strutureofthebody
swith(ID) {...
ase 0x0003: {
PIO_GPS_GGA arg = (PIO_GPS_GGA)GET_PARAM _POI NTER (); ...} ... }
The blok's PORT input speies ommuniation hannel. The outputs determine UTC time, LATitude,
LONgitudeand ALTitudeofatualposition,togetherwithQUALITYof GPSreading. Westressthat besidesthe
delarationsthereisnobodyinSTomponentoftheblok.
StruturetagIO_GPS_GGAdened atVMsiderepeatsSTdelarationswithalignment,speiestypename
and pointer type. Exeutions of C bloksare implementedby swith(ID)statementwith bodies entered at
suessiveases. SothebodyofGPS_GGAisenteredat ase 0x0003. FuntionGET_PARAM_POINTER()returns
pointer issavedin argvariable,suientforfurther proessing. OtherClanguagebloksare implementedin
thesameway. Givensuhtemplate,hardwaredesigners anprepareCbloksthemselves.
7. FBD and IL ompiler. The CPDev environment has been extended reently with simple graphi
editor of FBD diagrams and ompiler of IL textual language, mainly for teahing purposes. ST ompiler
remainsbasiplatformoftheenvironment.
7.1. Programmingin FBD. Thegraphieditor, alledBlokers(Fig.7.1),providesbasiediting
fun-tions,i.e. insertingbloksintodiagram,onnetinginputsandoutputsof thebloks,seleting andremoving
objets,zooming,et. ThebloksarehosenfromCPDevlibraries. Globalinput/outputvariablesandonstant
valuesarealso plaedin thediagram. Built-in syntax hekerveriesorretness. Resulting FBDdiagram is
savedin XML textle whosestruture followsreommendationsofPLCopen[13℄. TheXML leis then
on-verted into ST language by means of FBD2CPDev translator. Connetions between the bloks and instanes
of the bloks are representedby automatially reated loal variables of orrespondingtypes. Convention of
variablenamesisbasedontypesof bloksinthediagramandonexeutionorder.
Fig.7.1.FBDdiagramoftheSTART_STOPsystem
Figure7.1showsFBDdiagramoftheSTART_STOPsystemdrawnusingtheBlokerseditor. Numbersinthe
upperleft orners ofthe bloks indiate exeution order. Notiethat in aseof thefuntion bloks TON,TOF
thenumbersmaybeused to distinguishinstanes. Thevariablesplaedin narrowretangles onthe leftand
right areinterpreted asglobal. Equivalent ST ode generatedby FBD2CPDevtranslator is shown in Table 7.1
(ompareFig.3.2).
Table7.1
STprogramonvertedfromFBD
PROGRAM START_STOP
TON10 : TON;
VAR_EXTERNAL TOF11 : TOF;
START : BOOL; END_VAR
STOP : BOOL;
ALARM : BOOL; var_AND6_0 := AND(var_OR7_0,var_NOT9_0 ,va r_NO T8_ 0);
MOTOR : BOOL; var_OR7_0 := OR(var_AND6_0,START);
PUMP : BOOL; var_NOT8_0 := NOT(ALARM);
END_VAR var_NOT9_0 := NOT(STOP);
TON10(IN := var_AND6_0, PT := t#5s);
VAR TOF11(IN := TON10.Q, PT := t#5s);
var_OR7_0 : BOOL; MOTOR := var_AND6_0;
var_NOT9_0 : BOOL; PUMP := TOF11.Q;
var_NOT8_0 : BOOL;
Itisseenthat:
•
onnetionsbetweenthebloksare representedbyloal variablesvar_OR7_0to var_AND6_0;nameofavariable indiatessoureblokofthat variable,
•
twoinstanesTON10,TOF11arereated,withnamesinvolvingthebloktypeandexeutionorder.Outputsoftheinstanes,i.e.TON10.QandTOF11.Q,aredenotedin thestandardway(ompareFig.3.2).
7.2. Programming in IL. Sine delarationparts of programswrittenin ST andILare thesame,and
outomeof eahompilation is ale withVMASM ode,the ompilerof ILlanguagehasbeendevelopedby
extendingtheoriginalST ompiler. TheST ompilergeneratestheVMASModefrom expressiontreesbuilt
oftokensaquired from ST ode. Byanalysing asequeneofIL instrutionsoneanreate similartrees and
employtheminsuesivestagesofompilation,inthesamewayaswhileompilingST.Thisgivesmoreeient
VMASModethandiret translationofILinstrutionsintoVMASM,sineVMASM,unlikeIL,doesnotrely
onthenotionofaumulator. Aumulatorisnotneededinexpressiontrees,typialforhigh-levellanguages.
Table7.2
ILprogramforSTART_STOPprojet
PROGRAM PRG_START_STOP
LD START
VAR_EXTERNAL OR MOTOR
START : BOOL; ANDN STOP
STOP : BOOL; ANDN ALARM
ALARM : BOOL; ST MOTOR
MOTOR : BOOL;
PUMP : BOOL; CAL ON_DELAY(IN:=MOTOR, PT:=t#5s)
END_VAR CAL OFF_DELAY(IN:=ON_DELAY. Q, PT:=t#5s)
VAR LD OFF_DELAY.Q
ON_DELAY : TON; ST PUMP
OFF_DELAY: TOF;
END_VAR END_PROGRAM
ThePRG_START_STOPprogramof Fig 3.2is rewrittenin ILin Table7.2. TheinstrutionLD STARTloads
CRregister(CurrentResult;aumulatorinIEC)withthevalueofSTART.NexttheCRisORedwithMOTOR,with
theresultinCR.ThefollowingANDNnegates STOP,ANDsitwithCR,alwayswiththeresultinCR.Similarlyfor
anotherANDN.ST MOTORsavesCRin thevariable MOTOR.CALinstrutionsinvokefuntion bloks.
8. CPDev appliations. TheCPDevpakageisurrentlyappliedforprogrammingnewSMController
from LUMEL, Zielona Góra, Poland. SMC operates as a entral unit in small DCS systems involving
dis-tributedI/Omodules,intelligenttransmitters,PIDontrollers,et.[12℄. Developmentofanotherappliationin
forthomingversionofMINI-GUARDShipControl&PositioningSystemfromPraxisAutomationTehnology,
Leiden,TheNetherlands,isin progress[8℄. ForlabandteahingappliationsPC-basedsoftontrollersanbe
used.
8.1. SMC ontroller. The SMC shown in Fig. 8.1a is based on Atmel AVR 8-bit miroontroller.
Platform-dependent modules of virtual mahine, i. e. interrupts, RTC and ommuniation interfaes, have
beenwritten byLUMELengineers, and sent to theauthorsin binaryformat. Consolidationof universal and
LUMELmoduleshasresultedin aVM-SMCmahinewhih,asSMCrmware,exeutesSTprogramompiled
anddownloadedfromPC.Theontrollerisequippedwithtwoserialports,one(master)fordistributedI/Osand
elddevies,another(slave)forhostPCorHMIpanel. ModbusRTUprotoolisapplied(up to230.4kbaud).
ThirdComplex_blokslibrarytoimplementself-tuningPIDontrolloopsisprovided.
8.2. MINI-GUARD ontrollers. The MINI-GUARD system onsists of seven types of ontrollers
(Fig. 8.1b)involvingNXPARM7 16/32-bitmiroontrollers. The ontrollershaveappliation dediated
fae-plates. VirtualmahineforAtmelARM7hasbeensenttoPraxisA.T.,tobeadaptedfortheNXPARM7. The
softwaretohandleClanguagebloksdesribedinSe6.2hasbeendevelopedespeiallyforMINI-GUARD.The
ontrollersommuniate overEthernet,externaldeviesareonnetedviauniversalserial interfaeorOPC.
8.3. Softontrollers with NI and InTeCo boards. A PC equipped with I/O board and exeuting
a)SMController b)AlarmPanelofMINI-GUARD
)NI-DAQI/Oboard d)RT-DACI/Oboard
Fig.8.1.AppliationsofCPDevpakage
CPDev.CPCom.ICommDevhasbeendeveloped,withprovisionforothertypes. Softontrollerisonguredintwo
steps. First aboard isseletedfrom menuandI/Ohannelsdened. Thenglobal variablesoftheprojetare
linkedtothehannels. BinaryhannelsbeomeBOOLsandanalogoneREALs. Softontrollersanbeonneted
intoDCS systembymeansofModbusTCPprotool.
9. Conlusions and future work. CPDevenvironmentforprogrammingsmall ontrollersinST, FBD
and ILlanguagesof IEC 61131-3 standardhas been presented. The environmentis onsidered openbeause
ompiledodeanbeexeutedbydierentproessors,low-levelsoftwareomponentsareprovidedbyhardware
designers,andontrol programmersan reatetheirownlibrarieswithreusable programunits. Theompiler
produesuniversalexeutableodeproessedbyruntimevirtualmahineoperatingasinterpreter. Themahine
isanANSICprogramomposedofuniversalandplatform-dependentmodules. ThemahinesforAVR,ARM,
MCS51(ore)andx86proessorshavebeendevelopedsofar. Userfuntion bloksanbeprogrammedin ST
andC. TheSTbloksarekeptin CPDev libraries,whereasCbloksbeome omponentsof virtualmahine.
FBDdiagramistranslatedtoSTandthenompiled. CPDevhasbeenusedforprogrammingontrollersintwo
smallDCSsystemsandforPC-basedsoftontrollerwithI/Oboards.
simpleFBDeditor should beupgradedto moreprofessional level. Depending onST statementstheompiled
odeislongerorshorter,asintheexpressionx1 AND x2vs. funtionAND(x1, x2). Templatesindiatingmore
eient solutionsare important forthe users. Virtualmahine for FPGAplatform with simplemultitasking
mehanismisurrentlyunderdevelopment.
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Editedby: JanuszZalewski
Reeived: September30,2009
