NI Multisim：高级的捕捉与设计

NIMultisim：高级的捕捉与设计

NIMultisim：高级的捕捉与设计

Overview

Transformingadesignfromscribblesonanapkintoanorganizedand

professionalschematicisavitalstepinanyelectronicsdesign

process,andtheneedforaproductiveyetpowerfulcapturetoolis

critical.Asanycircuitdesignercanattestto,timeisavaluable

commodity,andisbetterspentonimportantdesignworkratherthan

learningtheidiosyncrasiesofadifficult-to-mastcrcapture

program.NationalInstrumentsMultisim(Figure1)isaprofessional

schematiccaptureandcircuitsimulationpackagethathasfocusedon

providingpowerfuldesignfeaturesthatintegrateseamlesslyintothe

applicationdesignflow.Thisintuitiveenvironmenthelpsany

engineertoeasily,successfullyandquicklycompletetheirdesigns.

Inprojectsofanycomplexity,Multisim'sadvancedcaptureprovides

benefitsbyofferingintuitivetoolsatalllevelsofschematic

capture:fromthefundamentalsofplacementandwiring,tothe

advancedfeaturesofprojectmanagementandcommunication.

Figure1.MultisimCaptureEnvironment

IntuitiveandEfficientCapture

Multisimcombinesanintuitivesimulationenvironmentwithadvanced

capturefeaturestoenheincedevelopment,reducerepetitivetasks,and

becomeanassettoanycircuitdesigner.Thetruebenefitsofthese

featuresareeasilyrealizedinMultisim,becausetheyare

implementedwithinaneasy-to-useenvironmentwithintuitive

interfaces.InthemajorityofEDAtoolstaskssuchascomponent

selection,placement,andwiringaretime-intensiveandlaborious.

Multisimhasbeendevelopedtobreakawayfromthisarduousmold.

Everyschematicbeginswiththeselectionandplacementofcomponents,

andasaresultanengineer,sinitialtaskistosearchtheir

capturetool'sdatabaseforspecificcomponents.Manytraditional

EDAtoolsarelumberedwithdisorganizeddatabasesthataredifficult

tonavigate.Inthesetools,componentselectionisahurdleinthe

designprocess.InMultisim,all17,000componentsinthemaster

databasearelogicallyorganizedintoeasy-tonavigategroups(Figure

2).Thesegrouj21ngsreflectthetypeofdeviceandfunctionality,so

thatcomponentssuchasdiodesareinonegroup,whileop-amps

populateaseparateanaloggroup.Thislogicalorganizationmirrors

thewaymostmanufacturerspresenttheirownpartslibraries,

providinganintuitiveinterfacethatanengineerhasencountered

manytimesbefore.

Figure2.Multisimdatabaseorganization

Withcomponentsselectedfromthedatabase,theengineerisfaced

withthesecondfundamentaltaskincapture:wiringtogether

individualcomponents.Inherentlythedesignprocessisquite

involvedasanengineercontinuouslynavigatestothedatabase,

searchesforandpicksapart,andthenwiresitintothedesign.In

manytraditionalEDAtools,anengineerwillquicklyrealizethat

wiringrequiresthemtorepeatedlyswitchbetweenplacementand

wiringmodesforeachnewcomponentandwiretobeplaced.Overthe

courseofanentiredesign,thisconstantswitchingcanborderupon

painfulforanengineer.InMultisim,thistediumiseliminatedbya

modelessenvironment,wherethemousecursor'sproximitytopinsand

otherconnectorswi1]automaticallyallowthedrawingofwires

(Figure3).Theabilitytoquicklycreateconnectionswithout

constantlyswitchingbetweendrawingmodesmakesthecaptureprocess

muchmoreefficient.

Figure3.EffortlesswiringintheMultisimmodelessenvironment

Withpartsplacedandconnectionscreated,evenasimpledesign

beginstoevolveintoaschematicofsizeandcomplexity.Devicesand

wiresspanasheet,makingthesearchforspecificelementssomewhat

difficult.Thisisanissuesincethenatureofthedevelopment

processistobeinastateofconstantchange,withelementsbeing

movedandeditedwhileadesignisimproved.Theabi1itytoeasily

manageandaccesstheseelementsacrossavastschematicis

extraordinarilyimportant.Foradesignofanyscope,theMultisim

spreadsheetview(Figure4)isadetailedtabularlistingofallnets

andcomponentsthatcanbesortedbyreferencedesignator,schematic

sheetandotherproperties.Theengineerbenefitsfromanorganized,

singleinterfaceinwhichtoviewandeditthepropertiesofthe

listeddesignelements.Thisspreadsheetviewgathersthe

functionalitythatcannormallyonlybeaccessedbyselectingthe

partitselfontheschematic.Thisoffersimmediateandcomprehensive

accesstoallelementsofacircuit.Fromthisspreadsheetview,a

footprintcanbechanged,apartreplacedandanetrenamed,

eliminatingthetryingtaskofsearchingacrossmultiplepagesand

numerousblockstoaccomplishthesameresult.

Figure4.ReplacingapartfromtheSpreadsheetView

Project-BasedDesign

Astheschematicevolvesinsizeandcomplexity,thedesigncan

naturallybecomecluttered,unreadableanddifficulttounderstand.

Designsofscalecanbebettermanagedandorganizedwithamodular

approachbysplittingthecircuit*sfunctionalityintoblocksthat

existacrossseveralschematicfiles(Figure5).Theproject

managementtoolsinMultisimprovideaneffectivemannerinwhichto

handleandkeeptrackofvariousfunctionalmodulesandtheir

respectiveinterconnectionswithinthegreaterdesign.Notonlydoes

thisefficientlyorganizeadesign,butitalsoresultsinre-usable

hierarchicalblocksthatcanbesharedamongmultipleprojectsand

teamsofengineers.

Figure5.ModulardesignwithHierarchicalBlocksinMultisim

Whenusinghierarchicalblocksformodulardesign,thenext

requirementofthecapturetoolistocentrallymanageallstagesof

thedesign,fromschematicstodatasheets,toproposalanddesign

documents.Thisentailsaproject-basedapproach,andisadvantageous

tobothtosmallsimpledesignsandmorecomplexandbroad-reaching

circuits.IntheMultisimenvironmentaprojectcanbedefined.

Throughthisprojectal1schematics,layoutfilesanddocumentscan

belinkedtogether.Thisorganizationcreatesasingleprojectthat

bindstheseparatepartsofadesignintooneentity,simplifyingthe

managementofallpartsofthedesignprocess,particularlyinteam

development.Whencollaborationextendsamongcubiclesorcontinents,

Multisimprovidesanorganizedwaytoeffectivelybringadesign

together.

DesignCommunication

Thecollaborativeprocessnurturedbyprojectmanagementcreatesa

realneedforeffectivecommunication.Engineersmaydevelop

individualsectionsofaschematic,however,itisimportantthat

anyonewhoviewsthedesignfullyunderstandeachofthesemodules

andthedesigndecisionsmade.Communicationisthereforeparamount

andschematicfeaturesandstatisticsneedtobefullyandclearly

conveyed.InMultisim,regionsofinterestandimportancecanbe

annotatedinastraightforwardmanner,withcommentsthatexist

directlyontheschematic.

Asthedesignapproachescompletion,thegroupofpeoplewithvested

interestintheprojectextendsbeyonddesignengineers,so

communicationmustbemorestructuredthaninsertedcommentsalone.

Others,whorevieworevaluateaproject,requiredetaileddesign

information.Reportingprovidesanorganizedsnapshotofadesignby

communicatingwhatiskeyintheevaluationofaprojectplan.Eor

example,aBillofMaterials(Figure6)canbegeneratedtolistall

componentsintheschematic,providingadetailedviewofwhat

devicesarerequiredtomanufacturethedesign.Thebenefitofany

reportinMultisimisthatitispopulatedautomaticallywitha

singlemouseclickenablingeffortlesscommunication.Majoraspects

ofthedesignarecoveredinthesereports,andtheycanbeeither

printedorexportedtoapplicationssuc