TEK 070-6863-00 ProductGroup38 24658/24678 OSCILLOSCOPES SERVICE [ 24678400MHz GPIBSTATUS .lOCK.SRQ .REM !.!oI / FOCUSREADOUTINTENSITY SCALE IlLUMrpOWEil BEAM TRACE Off fiND ROTATIONASTIG0

fACTORS fACTORS . Off ONCH1oRf3 lMI1 15pf::400Vpk 5011::5VRMS CH2CH3 (C-AIiBRATOR'< CH4 :Jl5Hz-5MHI1Ml1 15pf ::400VpklMI1 15pf::400Vpk!COMP PROBE@I"" i 1M11 15pf::400Vpk @e )@ () lillc: ywsun- 5011::5V RMS \.k....,._....",.__ TEK First Printing MAY1988 Revised SEP 1989 070-6863-00 Product Group 38 24658/24678 OSCILLOSCOPES SERVICE I WARNINGI THEFOLLOWINGSERVICINGINSTRUCTIONSARE FORUSEBYQUALIFIEDPERSONNELONLY.TO AVOIDPERSONALINJURY,DONOTPERFORMANY SERVICINGOTHERTHANTHATCONTAINEDIN OPERATINGINSTRUCTIONSUNLESSYOUARE QUALIFIEDTODOSO.REFERTOOPERATORS SAFETYSUMMARYANDSERVICESAFETYSUM-MARYPRIORTOPERFORMINGANYSERVICE. PleaseCheck for CHANGE INFORMA TION at theRear of ThisManual COMMITTED TO EXCELLENCECopyright@)1988Tektronix,Inc.Allrightsreserved. Contentsof thispublicationmaynotbereproducedinany formwithout thewrittenpermissionof Tektronix,Inc. Products of Tektronix,Inc.andits subsidiariesare covered byU.S.andforeignpatentsand/or pendingpatents. TEKTRONIX,TEK,SCOPE-MOBILE,and~are registeredtrademarksofTektronix,Inc. PrintedinU.S.A.Specificationandpricechangeprivileges arereserved. INSTRUMENT SERIAL NUMBERS Eachinstrument hasa serialnumber ona panelinsert,tag, orstampedonthechassis.Thefirstnumberorletter designatesthecountryofmanufacture.Thelastfivedigits oftheserialnumberareassignedsequentiallyandare uniquetoeachinstrument.Thosemanufacturedinthe UnitedStateshavesixuniquedigits.Thecountryof manufactureisidentifiedasfollows: BOOOOOO 100000 200000 300000 700000 Tektronix,Inc.,Beaverton,Oregon,USA TektronixGuernsey,Ltd.,ChannelIslands TektronixUnitedKingdom,Ltd.,London Sony/Tektronix,Japan TektronixHolland,NV,Heerenveen, TheNetherlands 2465B/2467B Service TABLEOFCONTENTS Page LIST OFILLUSTRATIONS ..................iii LIST OF TABLES .................................iv OPERATORSSAFETYSUMMARy....vi SERVICINGSAFETYSUMMARy .......vii SECTION1SPECIFICATION INTRODUCTION ..............................1-1 PERFORMANCECONDITIONS......1-1 SECTION2OPERATINGINFORMATION SAFETy ...........................................2-1 LINEVOLTAGESELECTION ..........2-1 LINEFUSE .......................................2-1 POWERCORD...... ............ .... .... ......2-1 INSTRUMENT COOLING ................2-1 OPERATINGINFORMATION ..........2-1 START-UP .......................................2-2 REPACKAGINGFORSHIPMENT ..2-2 SECTION3THEORYOFOPERATION (SNB050000 &ABOVE) INTRODUCTION ................................3a-1 SECTIONORGANiZATION .............3a-1 HYBRIDANDINTEGRATED CIRCUITDESCRIPTIONS ..............3a-1 BLOCK DIAGRAM...........................3a-1 BLOCK DESCRIPTION ...................3a-1 DETAILEDCIRCUIT DESCRIPTION3a-5 INTRODUCTION .......... ..... ....... ........3a-5 PROCESSORANDDIGITAL CONTROL........................................3a-5 FRONT-PANEL SCANNINGand ANALOGCONTROLS ..... ............ ....3a-9 FRONT-PANEL CONTROLS ...........3a-11 ATTENUATORSANDPREAMPS ..3a-13 DISPLAY SEQUENCER, TRIGGERS,ANDSWEEPS ............3a-17 VERTICAL CHANNELSWITCH ANDOUTPUT AMPLIFIERS ...........3a-23 READOUT .... ... ... ... ... ....... ....... ...... ....3a-27 HIGHVOLTAGEPOWERSUPPLY ANDCRTFOR2465BONLy ..........3a-35 HIGHVOLTAGEPOWERSUPPLY ANDMCP-CRT FOR2467B ONLY3a-40 LOW VOLTAGEPOWERSUPPLY.3a-46 LOW-VOLTAGEREGULATORS .....3a-51 POWERDISTRIBUTION .................3a-53 INTERCONNECTIONS ....................3a-53 SECTION3THEORYOFOPERATION (SNB049999 & BELOW) Page INTRODUCTION ................................3-1 SECTIONORGANiZATION .............3-1 HYBRID ANDINTEGRATED CIRCUITDESCRIPTIONS ..............3-1 BLOCKDIAGRAM ...........................3-1 BLOCKDESCRIPTION ...................3-1 DETAILEDCIRCUITDESCRIPTION3-5 INTRODUCTION ..............................3-5 PROCESSORANDDIGITAL CONTROL........................................3-5 FRONT-PANELSCANNINGand ANALOGCONTROLS ............... ......3-9 FRONT-PANEL CONTROLS ...........3-11 ATTENUATORSANDPREAMPS ..3-13 DISPLAYSEQUENCER, TRIGGERS,ANDSWEEPS ............3-17 VERTICAL CHANNELSWITCH ANDOUTPUTAMPLIFIERS ...........3-23 READOUT.. ... .......... ..... ... ..... .... ........3-27 HIGHVOLTAGEPOWERSUPPLY ANDCRTFOR2465B ONLy ..........3-35 HIGHVOLTAGEPOWERSUPPLY ANDMCP-CRTFOR2467B ONLY3-40 LOWVOLTAGEPOWERSUPPLY.3-46 LOW-VOLTAGEREGULATORS .....3-51 POWERDISTRIBUTION .................3-53 INTERCONNECTIONS ....................3-53 SECTION4PERFORMANCECHECKAND FUNCTIONALVERIFICATION INTRODUCTION ................................4-1 PREPARATION ................................4-1 VERTiCAL............................ ..............4-4 TRIGGERING .....................................4-15 HORIZONTAL. ...... .... ..... .... ... .............4-20 PARAMETRICMEASUREMENTS CHECK ...............................................4-27 COUNTER/TIMER/TRIGGER CH ECKS..... ....... ... .... .... ... ..... ...... ........4-29 HORIZONTAL (cont) .................... ......4-34 CALIBRATOR,EXTERNAL Z-AXISANDGATEOUTPUTS ..........4-36 ADDITIONAL FUNCTIONAL VERIFiCATION ...................................4-38 WORDRECOGNIZERCHECKS .......4-40 2465B/24678 Service TABLEOFCONTENTS(cont) Page SECTION5ADJUSTMENTPROCEDURE INTRODUCTION ...................... ..........5-1 PARTIAL PROCEDURE ..................5-2 PREPARATIONFOR ADJUSTMENT ...... .................. .........5-2 POWERSUPPLIESAND DACREFADJUSTMENTS................5-2 2467B CRT ADJUSTMENTS ............5-4 2465B CRT ADJUSTMENTS ............5-7 CH1 ANDCH2 INPUT CAPACITANCE,AND VERTICALREADOUT JITTER ADJUSTMENTS .................................5-10 AUTOMATIC CALIBRATION CONSTANTS,HORIZONTAL ANDVERTICAL GAIN, CENTERING,ANDTRANSIENT RESPONSEADJUSTMENTS............5-13 CAL 01-HORIZONTAL. .................5-13 CAL 02-VERTICAL .......................5-16 CAL 03-TRIGGERING ..................5-18 CAL 04-CH 2DELAY ENABLE/DISABLE ..........................5-19 CAL 05-Set HRSONand PWRON/OFF CyCLES ...................5-20 CAL 06-VERTICAL TRANSIENTRESPONSE................5-20 CAL 07-READOUT CENTERING ANDGAIN.... .............................. ......5-22 CAL 09-PARAMETRIC MEASUREMENTS .............. ............5-22 DYNAMIC CENTERING, DCBALANCE, AND X-YPHASEDIFFERENTIAL ADJUSTMENTS .................................5-25 SECTION6MAINTENANCE ii STATIC-SENSITIVE COMPONENTS6-1 PREVENTIVEMAINTENANCE..........6-2 INTRODUCTION.. .......... ..................6-2 GENERALCARE ............ .................6-2 INSPECTIONAND CLEANING.......................................6-2 LUBRICATION .................................6-4 SEMICONDUCTORCHECKS .........6-4 PERIODICREADJUSTMENT .........6-4 TROUBLESHOOTING .......................6-5 INTRODUCTION ................ ..............6-5 TROUBLESHOOTINGAIDS ...........6-5 TROUBLESHOOTING EQUIPMENT ....................................6-7 Page TROUBLESHOOTING TECHNIQUES ..................................6-7 DIAGNOSTICROUTINES.. ...... .......6-10 CORRECTIVEMAINTENANCE .........6-20 INTRODUCTION .......... ...... ..............6-20 MAINTENANCEPRECAUTIONS ....6-20 OBTAININGREPLACEMENT PARTS .............................................6-20 MAINTENANCE AIDS .....................6-21 INTERCONNECTIONS ....................6-21 TRANSISTORS,INTEGRATED CIRCUITS,ANDHYBRID CIRCUITS ........................................6-22 SOLDERINGTECHNIQUES ...........6-22 REMOVAL ANDREPLACEMENT INSTRUCTIONS ..............................6-24 SECTION7OPTIONS INTRODUCTION ..............................7-1 POWERCORDOPTIONS ...............7-1 OPTION01(2465B ONLy) ..............7-1 OPTION1R ......................................7-1 OPTION05............ ...... ........ ............7-2 OPTIONS06 AND09......................7-2 OPTION10 ......................................7-2 OPTION11......................................7-2 SECTION82465B REPLACEABLEELECTRICAL PARTS SECTION92467B REPLACEABLEELECTRICAL PARTS SECTION10DIAGRAMS ACRONYMDICTIONARY SECTION112465B REPLACEABLEMECHANICAL PARTS SECTION122467B REPLACEABLEMECHANICAL PARTS CHANGEINFORMATION Diagnostic and Troubleshooting Information: DIAGNOSTICROUTINES .................................6-10 TROUBLESHOOTINGCHARTS .......................SECTION10 24658/24678 Service LISTOFILLUSTRATIONS Figure 1-1246S8Dimensionaldrawing.. ..... ........... ............. ... ..... .... ...... ... ... .... ............... ........ ... ..... ... ..... ..... ...1-22 1-224678Dimensionaldrawing..........................................................................................................1-23 2-1Lineselectorswitch,linefuse,anddetachablepower cord ...... .......... ..... .... .... .... ... ..... .... ..... .......2-2 (For SN8050000 & Above) 3-1Instrumentblockdiagram ................................................................. ,............................................3a-2 3-1Instrumentblock diagram(cont) ....................................................................................................3a-3 3-2Addressdecoding .......................................................................................................................... 3a-7 3-3Front-panelswitchmatrix..................... ........ .................................................................................3a-12 3-4Scaleilluminationcircuit ................................................................................................................ 3a-16 3-SSweep generator ........................................................................................................................... 3a-22 3-6Developingthereadoutdisplay.....................................................................................................3a-28 3-7Readoutdisplay priorities .............................................................................................................. 3a-32 3-8Timingof RefreshPrioritizer..........................................................................................................3a-33 3-9Dcrestorer circuit(246S8 only).....................................................................................................3a-38 3-10Dcrestorer circuit(24678 only).....................................................................................................3a-43 3-11Timingrelationshipsof theInverterDrivesignals.........................................................................3a-48 3-12Simplifiedschematicof controlnetwork.......................................................................................3a-49 (For SN8049999 & 8elow) 3-1Instrumentblockdiagram ..............................................................................................................3-2 3-1Instrumentblockdiagram(cont) ....................................................................................................3-3 3-2Addressdecoding...................................................................................................................... ....3-7 3-3Front-panelswitchmatrix.............................................................................................................. 3-12 3-4Scaleilluminationcircuit................................................................................................................3-16 3-SSweepgenerator..................................................................................................................... ......3-22 3-6Developingthereadoutdisplay.....................................................................................................3-28 3-7Readoutdisplay priorities..............................................................................................................3-32 3-8Timingof RefreshPrioritizer..........................................................................................................3-33 3-9Dcrestorer circuit(246S8only).....................................................................................................3-38 3-10Dcrestorer circuit(24678 only).....................................................................................................3-43 3-11Timingrelationshipsof theInverter Drivesignals .........................................................................3-48 3-12Simplifiedschematicof controlnetwork.......................................................................................3-49 6-1MultipinConnectorOrientation.....................................................................................................6-6 6-2RibbonCableRemoval..................................................................................................................6-26 6-3PowerSwitchPush8uttonDisassembly ......................................................................................6-31 10-1Color codesforresistorsandcapacitors. 10-2Semiconductorleadconfigurations. 10-3Locatingcomponentsonschemcaticdiagramsandcircuitboardillustrations. 10-4Instrumentblockdiagram. 10-SAS-Control board. 10-6A6-Front Panelboard. 10-7A 1-Main andA8-Scale Illuminationboards. 10-8A 1S-Holdoff board. 10-9A 14-Dynamic Centeringboard. 10-10A4-Readout board. 10-11A9-24678 HighVoltageboard. 10-12A9-246S8 HighVoltageboard. 10-13A2-Regulator andA3-lnverter boards. Page iii 2465B/2467B Service iv Table 1-1 1-2 1-3 1-4 1-5 1-6 1-7 1-8 2-1 3-1 3-2 3-3 3-4 3-5 3-6 3-7 3-1 3-2 3-3 3-4 3-5 3-6 3-7 4-1 4-2 4-3 4-4 4-5 4-6 4-7 4-8 4-9 4-10 4-11 4-12 4-13 4-14 4-15 4-16 4-17 5-1 5-2 5-3 5-4 5-5 5-6 LISTOFTABLES Page 24658/24678 ElectricalCharacteristics ......... .... ....................... ........ ........ ....................................1-2 Option06(C/T/T)ElectricalCharacteristics ..................................................................................1-13 ResolutionSelections....................................................................................................................1-19 ResolutionSelections....................................................................................................................1-19 Option09(WR)ElectricalCharacteristics .....................................................................................1-20 24658 MechanicalCharacteristics ........ '"............ ... .... .... ..... ....... ....... .......... ... ..... ...... ........ .... .......1-21 24678 MechanicalCharacteristics ......... '"................................... '"....... ........ .......... ...... ...............1-22 EnvironmentalRequirements.........................................................................................................1-23 Power CordandVoltageData ......................................................................................................2-3 (ForSNB050oo0 & Above) Intensity Control ............................................................................................................................ 3a-19 TriggerSourceSelection...............................................................................................................3a-21 VerticalDisplaySelection ........... , ..................................................................................................3a-24 HorizontalDisplaySelection......................................................... .................................................3a-26 81ankingandIntensityControlSelection ......................................................................................3a-27 ReadoutDisplayMode Selection ..................................................................................................3a-31 Operationof PrioritizerShiftRegister...........................................................................................3a-32 (ForSNB049999 & Below) IntensityControl ............................................................................................................................ 3-19 TriggerSourceSelection ...............................................................................................................3-21 VerticalDisplaySelection ..............................................................................................................3-24 HorizontalDisplaySelection..........................................................................................................3-26 81ankingandIntensityControlSelection......................................................................................3-27 ReadoutDisplayMode Selection..................................................................................................3-31 Operationof PrioritizerShiftRegister...........................................................................................3-32 TestEquipmentRequired..............................................................................................................4-2 AccuracyLimits .............................................................................................................................. 4-7 AccuracyLimits .............................................................................................................................. 4-9 CH3andCH4AccuracyLimits...................................................................................................4-11 CH1 or CH2 TriggeringConditions.............................................................................................4-16 CH3 or CH4 TriggeringConditions.............................................................................................4-17 SettingsforAand8TimingAccuracyChecks............................................................................4-22 HorizontalTimingAccuracyCheckedAgainst theGraticule........................................................4-23 DeltaTimeDisplayAccuracy.........................................................................................................4-25 DelayedSweepDeltaTimeAccuracy...........................................................................................4-26 ParametricMeasurementPeriodChecks.....................................................................................4-27 ParametricMeasurementVoltsChecks.......................................................................................4-28 DataSetup TimeChecks..............................................................................................................4-41 DataHold TimeChecks.................................................................................................................4-42 MinimumClockPulseWidthChecks............................................................................................4-42 DelayFromSelectedEdgeto WORDRECOGOUTChecks......................................................4-43 WordRecognitionDelay................................................................................................................4-43 PowerSupplyVoltageandRippleTolerances ..............................................................................5-3 HorizontalTiming...........................................................................................................................5- 15 HorizontalTiming ................................................ " ... " ................. ,..................................................5-16 VerticalCalibrationSignals ............................................................................................................5-17 VerticalCalibrationSignals ............................................................................................................5-17 ParametricMeasurementCalibration ............................................... , ........... , ....................... ,........5-23 24658/24678 Service LISTOFTABLES(cont) 6-1SusceptibilitytoStaticDischargeDamage...................................................................................6-1 6-2ExternalInspectionCheckList. ..................................... " ............. " ...............................................6-2 6-3InternalInspectionCheckList .......................................................................................................6-3 6-4Sequenceof Diagnostic Tests .......................................................................................................6-11 6-5Sequenceof ExerciserRoutines...................................................................................................6-13 6-6KernelTestFailureCodes .............................................................................................................6-13 6-7Front-PanelLEDOptionCodes .....................................................................................................6-13 6-8Front-PanelLEDDeviceCodes.....................................................................................................6-14 6-9Potentiometer CodesandValues(Exerciser01) ..........................................................................6-16 6-1 0PotsandSwitchesColumn...........................................................................................................6-17 6-11NOPTest Data .............................................................................................................................. 6-19 6-12MaintenanceAids .......................................................................................................................... 6-21 v 24658/24678 Service OPERATORSSAFETYSUMMARY Thegeneralsafetyinformationinthispartofthesummaryisforbothoperatingandservicingpersonnel. Specificwarningsand cautionswill be foundthroughoutthe manual wherethey apply and do not appear inthis summary. Terms inThisManual CAUTIONstatementsidentifyconditionsorpracticesthat couldresultindamage to theequipmentor other property. WARNINGstatementsidentifyconditionsorpracticesthat couldresultinpersonalinjury or loss of life. Terms as Marked onEquipment CAUTIONindicatesapersonalinjuryhazardnotimmedi-atelyaccessibleasonereadsthemarkings,or a hazardto property,includingtheequipmentitself. DANGERindicatesapersonalinjuryhazardimmediately accessibleasonereadsthemarking. SymbolsinThisManual Thissymbolindicateswhereapplicablecau-tionaryor otherinformationistobefound.For maximuminputvoltageseeTable1-1. Symbolsas Marked onEquipment DANGER- Highvoltage. Protective ground(earth)terminal. ATIENTION- Referto manual. Power Source Thisproductisintendedtooperatefromapowersource thatwillnotapplymorethan250voltsrmsbetweenthe supplyconductorsor betweeneithersupplyconductorand ground.Aprotectivegroundconnectionbywayofthe groundingconductorinthepower cordisessentialforsafe operation. vi GroundingtheProduct Thisproductisgroundedthroughthegroundingconductor ofthepowercord.Toavoidelectricalshock,plugthe power cordintoa properlywiredreceptaclebeforemaking anyconnectionstotheproductinputoroutputterminals. Aprotectivegroundconnectionbywayofthegrounding conductor inthepower cordisessentialfor safe operation. Danger ArisingfromLossofGround Uponlossof theprotective-groundconnection,allaccessi-bleconductiveparts(includingknobsandcontrolsthat mayappear to beinsulated)canrenderanelectricshock. Use the Proper Power Cord Useonlythepowercordandconnectorspecifiedforyour product. Use onlya power cordthatisingood condition. Fordetailedinformationonpowercordsandconnectors, seeTable2-1. Use theProper Fuse Toavoidfirehazard,useonlyafuseofthecorrecttype, voltageratingandcurrentratingasspecifiedintheparts listforyourproduct. DoNot OperateinExplosiveAtmospheres Toavoidexplosion,donotoperatethisinstrumentinan explosiveatmosphereunlessithasbeenspecifically certifiedforsuchoperation. DoNot RemoveCovers orPanels Toavoidpersonalinjury,donotremovetheproductcov-ersorpanels.Donotoperatetheinstrumentwithoutthe coversandpanelsproperlyinstalled. 24658/24678 Service SERVICINGSAFETYSUMMARY FORQUALIFIEDSERVICE PERSONNELONL Y Refer a/sotothe preceding Operators Safety Summary. DoNot Service Alone Donotperforminternalserviceoradjustmentofthispro-ductunlessanotherpersoncapableofrenderingfirstaid andresuscitationispresent. Use CareWhenServicing WithPower On Dangerousvoltagesexistatseveralpointsinthisproduct. Toavoidpersonalinjury,donottouchexposedconnec-tionsor componentswhilepower ison. Disconnectpowerbeforeremovingprotectivepanels, soldering,or replacingcomponents. Power Source Thisproductisintendedtooperatefromapowersource thatdoesnotapplymorethan250voltsrmsbetweenthe supply conductorsor betweeneithersupplyconductorand ground.Aprotectivegroundconnectionbywayofthe groundingconductor inthepower cordisessentialfor safe operation. vii Specification-24658/24678 Service Characteristics CALIBRATOR Output VoltageandCurrent RepetitionPeriod Accuracy CH2SIGNAL OUT Output Voltage Offset AGATEOUT andBGATEOUT Output Voltage OutputDrive SourceVoltage NominalRanges 115 V 230 V SourceFrequency FuseRating MaximumPower Consumption (fully optioned instrument) PrimaryCircuitDielectricVoltageWithstandTest PrimaryGrounding Performance requirement not checked inmanual. 1-10 Table 1-1(cont) Performance Requirements SIGNAL OUTPUTS WithASEC/DIVset to 1 ms. 0.4V 1%intoa1-M12load,0.2V 1.5% intoa 50-12load,or 8 rnA 1 .5% into ashortcircuit. a Two timestheASEC/DIVsettingforSEC/DIVfrom100 nsto 100 ms. 0.1 %,duringsweeptime. 20 mV /division 10% into 1M12,10 mV /division 10% into 50 12. 20 mVinto 1 M12,whendc balancehasbeenperformedwithin 50 C of theoperatingtemperature. 2.4V to 5V positive-goingpulse,startingat0 V to 400 mV. Willsupply 400 J.LAduringHIstate;willsink2 rnAduringLOstate.a ACPOWERSOURCE 90 V to 132 V. 180 Vto 250 V. 48Hzto 440 Hz.a 2A,250 V,AGC/3AG,Fastblow;or 1.6 A,250V,5X20mm Quick-acting. a 120 watts (180 VA).8 1500 Vrms,60Hzfor10 secondswithoutbreakdown. a Type test to 0.112maximum.Routinetest to checkgrounding continuitybetweenchassisgroundandprotective earthground.a Section1-24658/24678 Service SPECIFICAliON INTRODUCTION TheTEKTRONIX24658and24678Oscilloscopesare portable400-MHzbandwidthinstrumentshavingfour-channelverticaldeflectionsystems.Channel1andChan-nel2providecalibrateddeflectionfactorsfrom2 mVper divisionto5Vperdivision.Foreachofthesechannels, inputimpedanceisselectablebetweentwovalues:either 1MQinparallelwith15pF,or50Q internaltermination. Input-signalcouplingwith1 MQimpedance canbeselected aseitherACorDC.Channel3andChannel4have deflectionfactorsofeither0.1Vor0.5Vperdivision. Eachof thesechannelshasaninputimpedanceof 1 MQin parallelwith15pF,withDCinput-signalcoupling. Thetriggersystemworksautomaticallyformostsig-nals.Theyoperateinvariousmodes,fromanychannel, withcouplingsforawiderangeofsignals.Thetrigger systemgivesstabledisplays fromdcto 500MHz. Thehorizontaldeflectionsystemprovidescalibrated sweepspeedsfrom1.5sperdivisionto500psperdivi-sion,includingtheeffectsoftheX10magnifierandthe calibratedvariablebetweenthe1-2-5steps.Horizontal displaysincludeA-Sweep,8-Sweep (delayed),A alternated with8,andCH1 (for X/Ydisplays). TheAUTO,SAVE,andRECALL featuressavetimeand preventerrors.PressingtheAUTOSetupbuttongivesa workablesetupforalmostanysignal.Forrepetitivemea-surements,theSaveandRecallfunctionsrecordand immediatelyorsequentiallyrestoreasmanyas30instru-mentsetups.TheSETUPbuttonsoperateallinstrument functions,includingtheextendedfunctionoptions. Direct,on-screenreadoutsoftimemeasurements,volt-agemeasurements,scalefactors,triggerlevels,and auxiliaryinformationalsosavetimeandimproveoperator confidence. The24678yields4 divisions/nsvisualwritingrate.This isabout100timesfasterthanconventional,high-performanceoscilloscopes.The24678visiblydisplaysany Signal,atanyrepetition-rate,atanysweepspeed,intypi-calroomlight.Visiblesingle-shotsinclude1nsstepsat 500ps/division. Theinstrumentsareshippedwiththefollowingstan-dardaccessories: 2Probepackages(24658) 4Probepackages(24678) 1Snap-lockaccessoriespouch 1Zip-lockaccessoriespouch 1Operatorsmanual 1Power cord(installed) 12-A,250-V fuse 1Clearplastic CRTfilter 181ueplasticCRT filter (installed) 1Front-panelcover 1Operatorspocket referencecard Forpartnumbersandfurtherinformationaboutboth standardandoptionalaccessories,referto"Optionsand Accessories"(Section7)oftheinstrumentsOperators manualortheAccessoriesinformationattherearofthis manual.YourTektronixrepresentativeorlocalTektronix FieldOfficecanalsoprovideaccessoriesinformationand orderingassistance. PERFORMANCECONDITIONS Thefollowingelectricalcharacteristics(Table1-1)are validfortheinstrumentwhenithasbeenadjustedatan ambienttemperaturebetween+20Cand+30C,has hadawarm-upperiodofatleast20minutes,andis operatingatanambienttemperaturebetween-15C and +55C (unlessotherwisenoted). Itemslistedinthe"PerformanceRequirements"column definethemeasurementcapabilitiesoftheinstruments. Supplementarymeasurementconditionsmayalsobelisted inthe"PerformanceRequirement"column. MechanicalcharacteristicsarelistedinTables1-6and 1-7. EnvironmentalcharacteristicsaregiveninTable1-8. Theoscilloscopemeetstheenvironmentalrequirementsof MIL-T-28800CforTypeIII,Class3,StyleCequipment, withthehumidityandtemperaturerequirementsdefinedin paragraphs3.9.2.2,3.9.2.3,and3.9.2.4. 1-1 Specification-24658/24678 Service Table1-1 24658/24678 Electrical Characteristics CharacteristicsPerformance Requirements VERTICALDEFLECTIONSYSTEM-CHANNEL 1 ANDCHANNEL2 DeflectionFactor Range Accuracy +15C to+35C On-GraticuleAccuracy ~V Accuracy(usingcursorsover entire graticule area) - 15 C to+ 15 C and+ 35 C to +55C 50 0Coupling CH2Inverted ~ VRange V/DIVVARiable,noninverted FrequencyResponse -3 dBBandwidth 5mVto 5V 2mV - 15 C to+ 15 C and+ 35 C to +55C 5 mVto 5 V 2mV aperformance requirement not checked inmanual. 2 mV /divisionto 5 V/divisionina1-2-5 sequenceof 11steps. 1 MOinput,noninverted. Within 2% atanyVOLTS/DIVsettingfora fouror five-division signalcenteredonthescreen. (1.25% of reading+0.03 div+signalaberrations). Add2% of reading.a Add 1%of reading. Add 1% of reading. 8XVOLTS/DIV setting.a ContinuouslyvariablebetweenVOL TS/DIVsettings.Extends deflectionfactorto> 12.5 V/division. Bandwidthismeasuredwithaleveled,low distortion,50-0source, sine-wavegenerator,terminatedin50O.Thereferencesignal amplitudeissetat thelesser of 6 divisions or themaximumleveled amplitude.Externalterminationbandwidthischeckwitha 4 division referencesignal. Bandwidthwithprobeis checkedusingaBNC-to-probe-tip (013-0227 -00) adapter. Bandwidth withexternalterminationischeckedusingaBNC50-0 feedthroughterminator(011-0049-01). Usingstandardaccessoryprobe or internal50-0 termination. Dcto 400MHz.b Dcto 350MHz.b Dcto 350MHz.a Dcto 300MHz.a blftheinstrumentissubjectedto"greaterthan"85%relativehumidity,bandwidthisreducedby50MHz.Aftertheinstrumentis subjectedto"greater than"85%relativehumidity,it requiresmorethan50hoursof operationat"less than"60%relativehumi-dity before fullbandwidth isrestored. 1-2 Specification-2465B/2467B Service Table1-1(cont) CharacteristicsPerformanceRequirements -4.7 dBBandwidthUsingSO-Qexternalterminationon1-MQinput. -1SoC to+3SoC S mVto S VDcto400MHz.b 2 mVDcto3S0MHz.b +3SoC to+SsoC S mVtoS VDcto3S0MHz.a 2 mVDcto 300MHz.a ACCoupled,Lower-3 dB10Hz or less. Frequency WithStandardAccessoryProbe1 Hzor less.a StepResponseRiseTimeCalculatedfromTr=0.3S/Bw.a S mVto S V ps. 2 mV ns. ChannelIsolation attenuationof deselectedchannelat100MHz;at 400MHz,foraneight-divisioninputsignalfromS mVper division toSOOmVperdivision,withequalVOL TS/DIVsettingsonboth channels. DisplayedChannel2 SignalAdjustablethrougha rangeof atleast-SOOpsto+SOOps.a DelaywithRespecttoChannel 1 Signal InputRand C (1MQ) Resistance1 MQo.s%.a Capacitance1SpF2 pF.a MaximumInput Voltage A DC,AC,or GNDCoupled400V (dc+peakac). 800Vp-pac.at10kHz or less. a InputR (SOQ) ResistanceSOQ1%.a VSWR Dcto 300MHz300to400MHzMaximumInputVoltage A S V rms,averagedfor1 second;SOVpeak.a CascadedOperationChannel2 VerticalSignalOutputintoChannel1 input;DCcoupled usinga SOQ RG-S8C/Ucoaxialcable,with1 MQDCor1 MQAC Channel1 input coupling;withChannel1 andChannel2 VOLTS/DIVsetat2 mVand20MHzBandwidthLimitOn. DeflectionFactor200 IJ. Vperdivision 10%. aperformancerequirement not checked inmanual. blftheinstrumentissubjectedto"greater than"85%relativehumidity,bandwidthisreducedby50MHz.Aftertheinstrumentis subjectedto"greater than"85%relativehumidity,itrequiresmorethan50hours of operationat"less than"60%relativehumi-dity before fullbandwidth is restored. 1-3 Specification-2465B/2467B Service Characteristics CMRR (ADDMode with Channel2inverted) Table1-1(cont) Performance Requirements At least 20: 1 at 50MHz for common-modesignalsof eight divisions or less,withVARVOLTS/DIV controladjustedfor best CMRRat 50 kHz,at anyVOLTS/DIV setting. VERTICALDEFLECTIONSYSTEM-CHANNEL 3ANDCHANNEL 4 DeflectionFactors Values100 mVand500 mVper division. AccuracyWithin 10%. FrequencyResponseBandwidthismeasuredwitha leveled,low distortion,50-Dsource, sine-wavegenerator,terminatedin50D.Thereferencesignal amplitudeissetat thelesser of 6 divisions or themaximumleveled amplitude.Externalterminationbandwidthischeckedwitha 4 divisionreferencesignal. BandwidthwithprobeischeckedusingaBNC-to-probe-tip (013-0227 -00) adapter. Bandwidthwithexternalterminationischeckedusinga BNC50-Q feedthroughterminator (011-0049-01). - 3 dB BandwidthUSingstandardaccessoryprobe. +15C to+35CDcto 400MHz.b - 15 C to+ 15 C and+ 35 C toDcto 350 MHz.a +55C -4.7 dBBandwidthUsing50-Qexternaltermination. +15C to+35CDcto 400MHz.ab - 15 C to+ 15 C and+ 35 C toDc to 350MHz.a +55C Step ResponseRise Time~ 8 7 5ps (calculatedfromTr=0.35/Bw).a ChannelIsolation~ 5 0 :1 attenuationof deselected channelat100 MHzwithan8-divisioninput signal. SignalDelayBetweenChannelWithin 1.0 ns,measuredat the50%pOints.a 1 andEitherChannel3 or Channel4 InputResistance1 MQ1%.a Input Capacitance15 pF3 pF.a MaximumInputVoltage & 400V (dc+peakac). 800V p-pacat10kHz or less.a aperformance requirement not checked inmanual. bittheinstrumentissubjectedto"greater than"85%relativehumidity,bandwidthisreducedby50MHz.Aftertheinstrumentis subjectedto"greaterthan"85%relativehumidity,itrequiresmorethan50hoursofoperationat"lessthan"60%relative humidity before fullbandwidth is restored. 1-4 Specification-24658/24678 Service Table1-1(cont) CharacteristicsPerformance Requirements VERTICALDEFLECTIONSYSTEM-ALL CHANNELS Low-frequencyLinearity BandwidthLimiter VerticalSignalDelay ChoppedMode SwitchingRate MinimumP-PSignalAmplitudeforStable Triggering fromChannel1 or Channel2Source DCCoupled NOISEREJCoupled ACCoupled H F R EJCoupled LFREJCoupled MinimumP-PSignalAmplitudeforStable Triggering fromADDSource MinimumP-PSignalAmplitudeforStable Triggering fromCH3 or CH4Source MinimumP-PSignalAmplitudefor Stable Triggering fromComposite,MultipleChannelSource,ALT VerticalMode aperformance requirement not checked inmanual. 0.1divisionor lesscompressionor expansionof a two-division, center-screensignalwhenpositionedanywherewithinthegraticule area. Reducesupper 3 dBbandpassto a limitof 13MHzto 24MHz. At least30nsof thesweep isdisplayedbeforethetriggeringevent isdisplayedatanySEC/DIV~10ns/div.At 5 ns/div,atleast10 ns of thesweepisdisplayedbeforethetriggeringevent. a WithdisplayedSEC/DIVinthe20J,LSto 2 J,Ls/divrange,the switchingrateis2.5MHz 0.2%.Otherwise,theswitchingrateis 1MHz 0.2%.Thedisplay cyclerateequalsthechopswitching ratedividedbythenumberof channelsdisplayed.Thechop switchingrateismodulatedslightlyto minimizewaveformbreaks withrepetitivesignals.a TRIGGERING 0.35 divisionfromdcto 50MHz;increasingto1.0 divisionat 300MHzand1.5 divisionsat500MHz. ~ 1 . 2divisions fromdc to 50MHz;increasingto 3 divisionsat 300MHzand4.5divisionsat500MHz. 0.35divisionfrom60Hzto 50MHz;increasingto1.0 divisionat 300 MHzand1.5 divisionsat500MHz.Attenuatessignalsbelow 60Hz. 0.5divisionfromdc to 30kHz. 0.5divisionfrom80kHzto 50MHz;increasingto1.0 divisionat 300MHzand1.5 divisionsat500MHz. Add0.5divisionto CH1 or CH2 requirementat 300MHz and 500MHz. 0.5XCH1 or CH2 requirement. Checkedat50mVper division. Add1 divisiontothesingle-channelsourcespecification. 1-5 Specification-2465B/2467B Service Characteristics MaximumP-PSignalRejectedbyNOISEREJ COUPLINGSignalsWithintheVerticalBandwidth CH1 orCH2 SOURCE CH3 or CH4SOURCE Jitter 2467B 246SB LEVELControlRange CH1 or CH2 SOURCE CH3 or CH4 SOURCE LEVELReadoutAccuracy CH1 or CH2 SOURCE + 1SoC to+3SoC -1SoC to+3SoC and+3SoC to +SsoC SOQ Input CH2Inverted NOISEREJCoupled CH3 or CH4 SOURCE NOISEREJCoupled AUTOLVLModeMaximumTriggeringSignalPeriod ASEC/DIVSetting 50 ms aperformance requirement not checkedinmanual. 1-6 Table1-1(cont) Performance Requirements divisionfor VOLTS/DIVsettingsof10mV/divandhigher. Maximumnoiseamplituderejectedisreducedat 2 mV /divand S mV/div. division.a pswithS divisions of 400MHzat SOOps/division. pswithS divisionsof 400MHz atSOOps/division. 18XVOL TS/DIVsetting.a 9XVOL TS/DIVsetting. a Fortriggeringsignalswithtransitiontimesgreater than20ns. Within [3% of reading+3% of p-psignal+0.2division+ O.SmV+(O.SmVXprobeattenuationfactor)]withVerticalInput at1 MQDC,CH2SourceNotInverted,andTriggerDCCoupled. Add1.SmVXprobeattenuationto+ 1S C to+ 3S C specification. a .. Add 1% to1 MQInputspecification. a Add 1% of readingto non-invertedspecification. a Add 0.6 divisiontoDCCoupledspecifications. a Within [3% of reading+4%of p-psignal+0.1division+ (O.SmVXprobeattenuationfactor)]andTriggerDCCoupled. Add0.3 divisionto theDCCoupledspecification. a Atleast20ms.a AtleastfourtimestheA-SEC/DIVsetting.a Atleast200ms.a REVOCT1988 Specification-2465B/2467B Service Table1-1(cont) CharacteristicsPerformance Requirements AUTOModeMaximumTriggeringSignalPeriod A-SEC/DIVSetting 50 msAt least800ms.a AUTOLVLMode TriggerAcquisitionTimeEightto 100 timestheAUTOLVLModemaximumtriggeringsignal period,dependingonthetriggeringsignalperiodandwaveform. TriggerHoldoff Minimum 2467BThegreater of theA-SEC/DIVsettingvalueor1 }.LS,within+33% +500nsto-10%.a 2465BThegreater of theA-SEC/DIVsettingvalueor 2 }.LS,within+33% to-10%, except1 }.LSat5 ns/div.a VariableIncreasestriggerholdoff timeto 10 to 25timestheminimum holdoff. SLOPESelectionConformsto trigger -sourcewaveformor acpower -source waveform. HORIZONTAL DEFLECTIONSYSTEM ASweep TimeBaseRange500ms/divto 5 ns/divina 1-2-5 sequenceof 25steps.X10MAG extendsmaximumsweeprateto 500ps/div. BSweep TimeBaseRange50ms/div to 5 ns/divina1-2-5 sequence of 22steps.X10MAG extendsmaximumsweeprateto 500ps/div. TimingAccuracy+ 15C to+35C, ASweep,withSEC/DIVat100 ms/div or faster. SweepAccuracyUnmagnified(0.7% of timeinterval+0.6%of fullscale). DotAccuracyWithCursors,Unmagnified (0.5% of timeinterval+0.3% of fullscale). DotAccuracywithSweepDelay (0.3% of timeinterval+0.1 % of fullscale+200 ps). DelayAccuracy,ASweep Trigger toStart of B(0.3% of delaysetting+0.6% of fullscale)+0 to-25 ns. Sweep B-SweepAccuracyandDotAccuracywithCursorsonAdd 0.3% of timeintervalto A-Sweepspecifications. BSweep aperformance requirement not checked inmanual. 1-7 Specification-2465B/2467B Service Characteristics X10MAGAccuracy 500msor 200ms/div TimingAccuracy (ASweep only) SEC/DIVVARTimingAccuracy TimingAccuracy(-15C to+15C and+35C to +55C) ~ tReadoutResolution ~ tRange SweepDelayRange Delay Jitter 2467B 2465B HorizontalPOSITIONRange X-Y Operation X-AxisDeflectionFactor Range,Variable,and Input Characteristics DeflectionFactor Accuracy X-AxisBandwidth PhaseDifferenceBetweenX andY withBW LimitOff X-AxisLow-frequencyLinearity aperformance requirement not checked inmanual. 1-8 Table 1-1(cont) Performance Requirements Add 0.5% of timeintervalto unmagnifiedSweepand~ tCursors specifications.Excludethefirst0.5 divisionafter thesweepstarts (thefirst0.5% of thefull100 divisionsweep). Add 0.5%of intervalto specificationsforASEC/DIVat100 ms or faster. Add2% of timeintervalto sweepaccuracyspecifications when V ARisout of detent. Add 0.2%of timeintervalto all~ tanddelayspecifications.Add 0.5% of intervalto sweepaccuracyspecification. a Greater of either10 ps or 0.025% of fullscale.a 10 timesA-SEC/DIVsettingwithCursors, 9.95timesA-SEC/DIVsettingwithSweepDelay.a o to 9.95 timestheASEC/DIVsetting,from500 msto10 ns.A-Sweep triggeringeventisobservable onBSweepwithzero delay settingfor ASEC/DIVsettings10 J.lsor faster.a Within0.01 % (onepart or lessin10,000) of themaximumavailable delay,plus100 ps.a Within0.004% (onepart or lessin25,000) of themaximum availabledelay,plus50ps. a Start of 1 msper divisionsweep canbepositionedfromrightof graticule center to at least10 divisionsleft of graticule center. Someportion of 1 ms per divisionsweep isalwaysvisiblewithX10 MAG off.a SameasChannel1. SameasChannel1. a Dcto 3 MHz. ~ 1 fromdc to 1 MHz;~ 3 from1 MHzto 2MHz. 0.1divisionor less compressionor expansionof a two-division, center-screensignalwhenpositionedwithinthegraticulearea. Characteristics CursorPositionRange DeltaVoltsDeltaTimeGraticule Size 24678 24658 Markings TraceRotationRange StandardPhosphor VisualWritingRate 24678 24658 PhotographicWritingSpeed(24678) DisplayIntensityLimitation(24678) Sensitivity Dcto2 MHz 2 MHzto 20MHz InputResistance MaximumInputVoltage.&. aperformance requirement not checked inmanual. Specification-2465B/2467B Service Table1-1(cont) Performance Requirements DISPLAY Atleast thecenter 7.6verticaldivisions. At leastthecenter9.6horizontaldivisions. 68mmX 85mm.a 80mmX 100 mm.a 8 major divisionsverticallyand1 0 major divisionshorizontally,with auxiliarymarkings. a Adequateto aligntracewiththe centerhorizontalgraticuleline. P31a divisions/ns. NOTE Usingthestandard-accessory c%r filter,no morethan5bright spotswill bevisibleat maximumintensity and no bright-spot halo will bevisiblewithinthecenter 7 X 9 divisions.Additional bright spots may bevisibleafter displaying a high-intensity trace.These added spotswill extinguishwhenintensity isset to minimum. divisions/f,Ls. 10 divisions/ns. Controlsettingsandtrigger ratearemonitoredtolimitthe display intensityafter a timeof nocontrolactivity. a Z-AXISINPUT Positivevoltagedecreasesintensity;+2 V blanksa maximum intensitytrace. +2 Vmodulatesa normalintensitytrace.a 9kQ 10%.a 25 V peak;25V p-pacat10kHzor less.a 1-9 Specificatioii-24658/24678 Seii;ice Table1-1(cont) CharacteristicsPerformance Requirements PARAMETRICMEASUREMENTS Period Accuracy + 15C to+35C0.9%+0.5ns+Jitter Error. - 15to+ 15 C andAdd0.3%. +35C to+55C MinimumPeriod::::;;2ns. MaximumPeriod~ 1 0 0ms(MINFREQ=10Hz). MinimumSignalAmplitude ::::;;(60mV+probeattenuationfactor p-p). IfDCcouplingisused,theDCoffset voltagemustmeetthe followingcriteria: ata VOLTS/DIV settingwhichgivesa p-pSignal~4 divisions, thepeaksignal+offset mustbe::::;;12divisions. FrequencyCalculatedas1/period. Volts + Peak,- Peak,Peak-to-Peak,andAverage Accuracy + 15 C to+ 35 C5%of reading+5 mV+(0.5mV*probeattenuation)+signal aberrations+1LeastSignificantDigit(LSD). - 15 C to+ 15 C andAdd(1.5mV*probeattenuation). +35C to+55C MinimumWidthatPeakAmplitude::::;;10ns. MaximumSineWaveFrequency + 15 C to+ 35 C~1MHz. - 15 C to+ 15 C andAdd2%. +35C to+55C Voltsmeasurementsdependonpeaksignalmeasurements. Noiseontheinputsignal,evenifata low repetitionratethat makesit difficultto see,willbedetectedandwillaffect the measurements. PulseWidth(Highor Low) Accuracy + 15 C to+ 35 C0.9% of reading+1.0 ns+jitter error+2 *offset error. - 15 C to+ 15 C andAdd0.3%. 35C to+55C MinimumPulseWidth::::;;5 ns. MinimumRepetitionRate::::;;10Hz (withMINFREQ=10Hz). REVOCT1988 1-11 Specification-2465B/2467B Service Characteristics Duty Cycle RiseTime,FallTime,andTimeInterval Accuracy Rise/FallTime TimeInterval - 15 to+ 15 C and +35C to+55C MinimumTime MinimumRepetitionRate Jitter Error 1-12 Table1-1(cont) Performance Requirements CalculatedfromPulseWidthandPeriod. 5% of reading+3.0ns+jitter error+offset error. Add0.5nsif measurementismadebetweenCH1andCH2. 0.5 %of reading+5% of start eventtransitiontime+5% of stop event transitiontime+3.0 ns+ jitter error+ offset error. RiseandFalltimemeasurementismadeat 20% and80% points of transitionandlinearlyextrapolatedto the10% and 90% pOints. Accuracyisrelativeto timeintervalasmeasuredonscreen using cursors.Measurementismade usingpeak-to-peak transitionfor measurementpointsinpercent. Add2%. ~5 ns. ~10 Hz(withMINFREQ=10 Hz). Noise onthe input signalcausesjitter whichintroduceserrorsin themeasurements.Theamount of jitter dependsonthenoise amplitudeandtheslew rateof theinputsignals. Theamount of jitter canbe calculatedas: Input slew rateshouldbemeasuredat2 Volts/div.settingsmore sensitivethanthe settingat the endof themeasurementsor at 5 mV/div,whicheveris lesssensitive. Theslewratemust bemeasuredatthesamepOintsatwhich themeasurementwillbe taken.ThepOintsfor thevarious measurementsare: Measurement Frequency Width Rise,FallTime Timeinterval Measurement Points First Measurement point 50% amplitude 50% amplitude Second Measurement pOint 50%amplitude 50%amplitude 10% amplitude90% amplitude Specifiedby TimeSpecifiedbyTime IntervalConfigurationIntervalConfiguration REVOCT1988 Characteristics OffsetError Specification-2465B/2467B Service Table1-1(cont) Performance Requirements Thealgorithmsusedfor themeasurementsresultinthe followingequationfor thetotaljitter error thatmustbeapplied totheaccuracyspecifications. Jitter Error=2 *firstpoint jitter + 2 *secondpoint jitter. Offset error isintroducedwhenthetriggerlevelisnotset exactlyattheexpectedpOints.Thismisplacementof thetrigger levelappliedto anynon-infiniteslewrateproducesa timing error.Themagnitudeof the errorisgivenby: OffsetError=.offset Inputslewrate Frequencymeasurementsdonotsuffer fromoffset errorssince measurementsaremadewiththesametriggerlevelandslope, sono offset isintroduced. Allother timingmeasurementssufferfromoffset errors. Theslewratesusedto calculateoffset errorsmustbemeasured atthefirstandsecondmeasurementpoints giveninthe MeasurementPointstable. Offset error iscalculatedas: OffsetError=0.2 div FirstPointslewrate 0.2div +SecondPointslewrate If a timeintervalmeasurementismadeusingVoltsmode,the offsetat eachmeasurementpOintis: 0.2div+ 5%of measurementpointvoltageconvertedto divisions. 1-13 Specification-2465B/2467B Service Table1-2 Option 06(CIT IT)Electrical Characteristics Characteristics MaximumInputFrequencyforCountandDelayby Events MinimumWidthof HighorLow State of InputSignal for CountandDelaybyEvents Sensitivity Dcto 50MHz (0.5Hzto50MHz for FrequencyandPeriod) CH1 andCH2 CH3andCH4 50MHzto150 MHz CH1 andCH2 CH3andCH4 Ranges AutomaticRanging aperformance requirement not checkedinmanual. Performance Requirements SIGNAL INPUT WithDCCouplingof A TriggerandB Trigger. ~ 1 5 0MHz. =s:;3.3ns. For Count,DelaybyEvents,andLogicTriggerFunctions ExcludingWordRecognizer. 1.5 divisions. 0.75 division. 4.0 divisions. 2.0divisions. FREQUENCY RANGELS08 1 Hz100 nHz 10 Hz1 ~ H z 100 Hz10 ~ H z 1 kHz100 ~ H z 10 kHz1 mHz 100 kHz10 mHz 1 MHz100 mHz 10 MHz1 Hz 100 MHz10 Hz 150 MHz100 Hz Uprangesat100% of fullscale;downrangesat9% of full scale.Downrangeoccursat90MHzon150MHzrange. FullscalecorrespondstothevaluegivenintheRange column.Themaximumdisplayedvalueforanyrangeisthe RangevalueminustheLSDvalue. Characteristics Accuracy TimeBaseError (TBE) Resolution DisplayUpdateRate Ranges MinimumPeriod AutomaticRanging Accuracy Resolution DisplayUpdateRate aperformance requirement not checked in manual. Specification-2465B/2467B Service Table1-2 (cont) Performance Requirements [Resolution+ (FrequencyXTBE)]Hz. 10 ppmwithlessthan5 ppmper yeardrift. 1.4XFreguency2XTJE+ LSD N. Twiceper secondor twice theperiodof theinputsignal, whicheverisslower. PERIOD RANGE 10 ns 100 ns 1 ,.,.s 10,.,.s 100,.,.s 1 ms 10 ms 100 ms 1 s 2s ~ 6 . 7ns. Uprangesat 100% of fullscale; downrangesat 9% of fullscale. LSD8 1 fs 10 fs 100 fs 1 ps 10 ps 100 ps 1 ns 10 ns 100 ns 1 ,.,.s Fullscalecorrespondsto thevaluegivenintheRange column.Themaximumdisplayedvaluefor anyrangeisthe RangevalueminustheLSDvalue. [Resolution+ (TBEXPeriod)]. [LSD+ (1.4XT JE)/N]. Twiceper secondor twice theperiodof theinputsignal, whicheverisslower. 1-15 Specification-2465B/2467B Service Characteristics MaximumCount DisplayUpdate Rate MaximumEventCount Minimum Time fromStartSignal to AnyDelayEvent MinimumFunction-True Time MinimumFunction-FalseTime Table 1-2 (cont) Performance Requirements TOTALIZE 9999999. Twiceper second or onceper event,whichever isslower. DELA Y BYEVENTS 4194303. 4ns. LOGICTRIGGER 4 ns. 4ns. ADDEDDELAYTIMECHARACTERISTICSWITHCITIT RunAfterOelay Accuracy TriggerableAfterDelay Accuracy MinimumMeasurableDelayTime DisplayUpdateRate bSee Tables1-3 and1-4. CBTime/Div includes SEC/DIV,X10MAG,andVAR. LSOb+ [0.0012X(ASEC/DIV)]+ [0.03X(BTime/Div)C]+ A TriggerLevelError+ 50 ns. WhentheASweep istriggeredby theWordRecognizer in synchronousmode,add100 nsfor probe delay;inasynchronous mode,add 200 ns for probe delay. For intervalswithin70 ns to 10 times theA-SEC/DIVSetting. LSOb+ [10ppmX(measuredinterval)]+ TJE+ A-TriggerLevel Error+ B-TriggerLevelError+ 0.5ns. If theAandBSweepsaretriggeredfromdifferent channels,add 0.5nsfor channel-to-channelmismatch. WhentheASweep istriggeredby theWordRecognizer in synchronousmode,add100 ns for probe delay;inasynchronous mode,add 200 ns for probe delay. ~ 7 0ns. InAutoResolution,twice per secondor once for everysweep, whicheverisslower. In1 ns,100 ps,andlOps resolutionmodes,theupdate rate depends ontheASEC/DIV settingandthe triggerrepetitionrate. dThistermassumes the trigger points arebetween the10%and 90%points of the waveforms.Falltime is expressed as a negative risetime. 1-16 Specification-2465B/2467B Service Table 1-2 (cont) CharacteristicsPerformance Requirements ADDEDDEL TA-DELA Y-TIMECHARACTERISTICSWITHCIT IT RunAfterDelay Accuracy TriggerableAfterDelay Accuracy SuperimposedDeltaTime NonsuperimposedDelta Time DisplayUpdateRate bSeeTables1-3 and1-4. CBTime/Div includes SEC/DIV,X10MAG,and VAR. LSDb+ [0.0008X(ASEC/DIV)]+ [0.01X(8 Time/Div)C]+ 83 ps. WhentheASweep istriggeredby the WordRecognizerin synchronousmode,add1 nsfor probe jitter;inasynchronous mode,add20ns for probe jitter. 80th delaysarewithin70nsto 10 timestheA-SEC/DIVsetting. LSDb+ [0.01X(8 Time/Div)C]+ [10 ppmX(ASEC/DIV)]+ [10 ppmX(measuredinterval)]+ 50ps+ T JE. If CH3 or CH4 isone channelof a two-channelmeasurement,add 0.5ns for channel-to-channeldelay mismatch. LSDb+ I trREF- trOELTI d+ T JE+ [(0.0005div)X(1/SRREF + 1/SROELT)]+ [10ppmX(ASEC/DIV)]+ [10ppmX(measuredinterval)]+ 50 ps. If A and8sweeps aretriggeredfromdifferent channels,add0.5ns for channel-to-channelmismatch+ [0.5 divX(1/SRREF + 1/SROELT)]for trigger offset. InAutoResolution,twice per secondor once for every four sweeps,whicheverisslower. In1 ns,100 ps,and10 psresolutionmodes,theupdaterate depends onthe ASEC/DIV settingandthetrigger repetitionrate. dThistermassumes the trigger paints are between the10%and 90%points of the waveforms. Falltime is expressed as a negative risetime. 1-17 Specification-2465B/2467B Service Table1-2 (cont) Characteristics DEFINITIONS ATriggerLevelError=(A TriggerLevelReadoutError)/SRA. 8TriggerLevelError=(8 TriggerLevelReadoutError)/SRs' trREF=risetime,referencetriggersignal. trOEL T=risetime,delta triggersignal. SRA =slew rateat trigger point,ASweep triggersignalindiY/sec. SRs=slew rateat trigger pOint,8Sweep triggersignalindiY/sec. SRREF=slewrateattriggerpOint,referencetrigger signalindiY/sec. SROEL T=slewrateattriggerpoint,deltatriggersignalindiY/sec. TJE=trigger jitter error. Performance Requirements For delay or delta time,disregardingnoiseinthesignal,thistermcontributes104 >100 >104 >100 >100 >1 >1 >1 N forAverage >104 >100 >100 >1 >1 >1 >1 1-19 Specification-2465B/2467B Service Table 1-5 Option 09 (WR) Electrical Characteristics CharacteristicsPerformance Requirements SYNCHRONOUSMODE DataSetup Time 00-015 andQ DataHold Time 00-015 andQ MinimumClockPulseWidth High Low MinimumClockPeriod DelayfromSelectedClockEdgeto WordOut from C/T/T 25ns. o ns. 20 ns. 20 ns. 50 ns. ~ 5 5ns. ASYNCHRONOUSMODE MaximumTriggerFrequency Minimum CoincidenceBetweenDataInputs (00-015 & Q)Resultingina Trigger Maximum CoincidenceBetweenDataInputs (00-015 & Q)WithoutProducinga Trigger DelayfromInput WordCoincidence to WordOut 10 MHz. 20 ns. ~ 1 4 0ns. INPUTS AND OUTPUTS Input Voltages MinimumInputVoltageA MaximumInput VoltageA MaximumInputLow Voltage MinimumInput HighVoltage WORDRECOGOUT High Low InputHighCurrent InputLowCurrent 1-20 -0.5 V. 5.5V. 0.6 V. 2.0 V. >2.5VLSTTL output. w CD A AMPLIFIERa: -SWEEP 0 A DELAYSATE' 8 f---- B TRIS SWEEP B DlYSATE .. --0 B SWEEP 6863-33 Figure 3-1.Instrument block diagram (cont). 3-3 Theory of Operation-24658/24678 Service Mostoftheactivitiesoftheinstrumentaredirectedby amicroprocessor.Themicroprocessor,underfirmware control(firmwareistheprogrammedinstructionscontained inread-onlymemorythattellstheprocessorhowto operate),monitorsinstrumentfunctionsandsetsupthe operatingmodesaccordingto theinstructionsreceived. VarioustypesofdatareadtoandfromtheMicropro-cessor(programinstructions,constants,controldata,etc.) arealltransferredovera groupof eightbidirectionalsignal linescalledtheDataBus.TheDataBusisdedicated solelytomicroprocessor-relateddata transfer. Anothergroupofsignallines,calledtheAddressBus, areresponsibleforselectingor"addressing"thememory locationordevicethattheMicroprocessorwantstocom-municatewith.Typically,dependingontheinstruction beingexecuted,theprocessorplacesanaddressonthe AddressBustoidentifythelocationtheMicroprocessor mustcommunicatewith.Thisaddress,alongwithsome enablinglogic,opensupanappropriate data pathbetween theprocessorandthedeviceormemorylocationviathe DataBus;anddataiseitherreadfromorwrittentothat locationbytheprocessor. Whileexecutingthecontrolprogram,theMicroproces-sorretrievespreviouslystoredcalibrationconstantsand front-panelsettingsand,asnecessaryplacesprogram-generateddataintemporarystorageforlateruse.The batterybackedupRAMprovidesthesestorage functions. Whenpowerisappliedtotheinstrument,a briefinitiali-zationsequenceisperformed,andthentheprocessor beginsscanningthefront-panelcontrols.Theswitchset-tingsdetectedandtheretrievedfront-paneldatafromthe batterybackedupRAMcausestheprocessortosetvari-ouscontrolregistersandcontrolvoltageswithintheinstru-mentthatdefinetheoperatingmodeoftheinstrument. Theseregistersettingsandvoltagelevelscontroltheverti-calchannelselectionanddeflectionfactors,thesweep rate,thetriggeringparameters,thereadoutactivity,and sequencingofthedisplay.Loadingthecontroldatainto thevariousregistersthroughouttheinstrumentisdone usingacommonserialdataline(CD).Individualcontrol clocksignals(CC)determinewhichregisterisloadedfrom thecommondataline. Coordinationofthevertical,horizontal,andZ-Axis (intenSity)componentsofthedisplaymustbedoneinreal time.Duetothespeedofthesedisplaychangesandthe precisetimingrelationshipsthatmustbemaintained betweendisplayevents,directsequencingofthedisplayis beyondthecapabilitiesoftheprocessorcontrol.Instead, controldatafromtheprocessorissenttotheDisplay Sequencer(aspecializedintegratedcircuit)whichresponds 3-4 bysettingupthevarioussignalsthatcontrolthestages handlingreal-timedisplaysignals.Thecontrolledstages aresteppedthroughapredefinedsequencethatisdeter-minedbythecontroldata.Typically,asthesequenceis beingexecuted,theDisplaySequencerwillbechanging verticalsignalsources,Z-Axisintensitylevels,triggering sources,andhorizontalsweepsignalsources.Thespecific activitiesbeingcarriedoutbytheDisplaySequencer dependonthedisplaymodecalledforbythecontroldata. Verticaldeflectionforcrtdisplayscomesfromoneor moreofthefourfront-panelverticalinputsand,when displayingreadoutinformation,fromtheReadoutcircuitry. Signalsappliedtothefront-panelChannel1andChannel 2 inputsareconnectedto theirrespectivePreamplifiersvia processor-controlledAttenuatornetworks.Controldata fromtheMicroprocessor definingtheattenuationfactorfor eachchannelisseriallyloadedintotheAuxiliaryControl RegisterandthenstrobedintotheAttenuatorMag-Latch Relaysinparallel.TherelayswitchesofeachAttenuator networkareeitheropenedorclosed,dependingonthe datasuppliedtotheMag-LatchRelayDrivers.Therelays aremagneticallylatchedandremainassetuntilnewcon-troldataisstrobedin.TheAuxiliaryControlRegisteris thereforeavailable,anddifferentmodedataisclockedinto theregistertosetupotherportionsof theinstrument. AttenuatedChannel1andChannel2inputsignalsare amplifiedbytheirrespectivePreamplifiers.Thegainfactor fortheChannel1andChannel2Preamplifiersissettable bycontroldatafromtheprocessor.TheChannel3and Channel4inputsignalsareamplifiedbytheirrespective Preamplifiersbyeitheroftwogainfactorssetbycontrol bitsfromtheAuxiliaryControlRegister.Allfourofthese preamplifiedsignalsareappliedtotheVerticalChannel SwitchwheretheyareselectedbytheDisplaySequencer for display whenrequired. EachoftheverticalsignalsisalsoappliedtotheA and BTriggerCircuitryviatriggerpickoffoutputsfromthe Preamplifierstages.Anyoneofthesignalsmaybe selectedasthetriggerSOURCEforeithertheA ortheB Trigger CircuitryasdirectedbytheDisplaySequencer.The linetriggersignalprovidesanaddedtriggersourceforA Sweepsonly.ControldatafromtheMicroprocessoris writtentotheTriggercircuitrytodefinethetriggering LEVEL,SLOPE,andCOUPLINGcriteria.Whenthe selectedtriggersignalmeetstheserequirements,a sweep canbeinitiated.TheTriggercircuitinitiatesboththeA SweepandtheBSweepasrequiredbythedisplaymode selected. InthecaseofASweeps,theLOstateoftheTHO (triggerholdoff)signalfromtheDisplaySequencerenables theASweepcircuitandthenextAtriggerinitiatesthe sweep,For8sweeps,andinthecaseofintensified sweeps,theASweepdelaygatesignal(DG)enablesthe BSweepcircuit.DependingontheBtriggermode selected,aBSweepwillbeinitiatedeitherimmediately (RUNAFTDL Y)oronthenextB triggersignal(TRIGAFT DLY).Theslopeofthesweeprampisdependenton Microprocessor-generatedcontroldataloadedintothe internalcontrolregisteroftheAandBSweepcircuit hybrids. Sweepsignalsgeneratedbyeachof theSweephybrids areappliedtotheHorizontalAmplifier.TheHorizontal AmplifierisdirectedbytheDisplaySequencertoselect oneofthesweeprampsforamplificationinsequence.In thecaseofReadoutandX-Y displays,theX-Readoutand CH1 inputsignalsareselectedtobeamplified,alsounder directionof theDisplaySequencer. Tocontrolthedisplayintensity,theDisplaySequencer directstheZ-Axiscircuittounblankthedisplayatthe appropriatetimeforthesweepsandreadoutdisplays. Whenthedisplayisunblanked,theDisplaySequencer TheoryofOperation-2465B/2467B Service selectsthedisplayintensityforeitherwaveformdisplays orforreadoutdisplaysbyswitchingcontroloftheZ-Axis beamcurrentbetweenthefront-panelINTENSITYand READOUTINTENSITYpotentiometersasappropriate. Duringreadoutdisplays,theverticaldot-positionsignal fromtheReadoutcircuitryisappliedtotheVertical AmplifierviatheVerticalChannelSwitch.Horizontaldot-positiondeflectionforthereadoutdisplayisselectedby internalswitchingintheHorizontalAmplifier. Thevertical,horizontal,andZ-Axissignalsareapplied totheirrespectiveamplifierswheretheyareraisedtocrt-drivelevels.TheoutputsignalsfromtheVerticalandHor-izontalAmplifiersareapplieddirectlytothecrtdeflection plates.TheZ-AxisAmplifieroutputsignalrequiresinterfac-ingtothehigh-potentialcrtenvironmentbeforeapplication tothecrtcontrolgrid.ThenecessaryZ-Axisinterfacingis providedbytheDCRestorercircuitlocatedontheHigh-Voltagecircuitboard.Theresultingdisplaymaybeof waveforms,alphanumericreadout,oracombinationof both. DETAILEDCIRCUITDESCRIPTION INTRODUCTION Thefollowingdiscussionprovidesdetailedinformation concerningtheelectricaloperationandcircuitrelationships oftheinstrument.Circuitryuniquetotheinstrumentis describedindetail,whilecircuitscommonintheelectronics industryarenot.Thedescriptionsareaccompaniedby supportingillustrationsandtables.Diagramsidentifiedin thetext,onwhichassociatedcircuitryisshown,are locatedattherearofthismanualinthetabbedfoldout pages. PROCESSORANDDIGITALCONTROL TheProcessorandDigitalControlcircuitry(diagram1) directstheoperationofmostoscilloscopefunctionsbyfol-lowingfirmwarecontrolinstructionsstoredinmemory. TheseinstructionsdirecttheMicroprocessortomonitor thefront-panelcontrolsandtosendcontrolsignalsthat setupthevarioussignalprocessingcircuitsaccordingly. Microprocessor TheMicroprocessor(U2140)isthecenterofcontrol activities.Ithasaneight-bit,bidirectionaldatabusfordata displaytransfer(DOthrough07)anda16-bitaddressbus (AOthroughA 15)forselectingthesourceor destinationof thedata.Precisetimingofinstructionexecution,address-ing,anddatatransferisprovidedbyanexternal,crystal-controlledclocksignal. TheclocksignalisdevelopedbytheMicroprocessor ClockstageandappliedtotheMicroprocessoratpin39. Usingtheexternalclockasareference,theMicroproces-sorgeneratessynchronizedcontroloutputsignals,R/W (read-write),E(enable),andVMA(validmemoryaddress) thatmaintainpropertimingrelationshipsthroughoutthe instrument. Microprocessor Clock TheMicroprocessorClockstagegeneratesa5-MHz square-waveclocksignaltotheMicroprocessoranda10-MHzclocksignaltoportionsoftheReadoutcircuitry. InverterU2540AactsasanoscillatorwithcrystalY2540 providingfeedbackattheresonantfrequency.The requiredphaseshiftforoscillationtooccurisproducedby C2550,C2551 ,R2545,andthecrystal.TheRCnetwork composedofR2543,C2640,R2541 ,andR2542biases inputpin1 ofU2540Aintheactiveregionandestablishes approximatesymmetryoftheoscillatoroutput.Thesignal isbufferedandinvertedbyU2540Btoprovidethe10-MHz clocksignal. 3-5 Theory of Operation-2465B/2467B Service Flip-flopU2440Aisadivide-by-twocircuitthatreduces the10-MHzclockdowntoa5-MHzsquare-wavesignal usedtoclocktheMicroprocessorandtheDisplay Sequencer.The10-MHzclockissuppliedtotheReadout Boardfordottimingandisalsoavailableforusewith option circuitry. Reset Control TheResetControlcircuitryensuresthat,atpowerup, theMicroprocessorbeginsprogramexecutionfroma knownpointinmemoryandwithalltheprocessorregis-tersinknownstates.Italsoallowstheprocessortoreset itselfwhenpoweristurnedoffsothattheinstrument powers downina knownstate. POWERUPSEQUENCE.ResetgeneratorU2240 generatesthepower-upreset.Aspowerisappliedtothe instrumentU2240teststhevoltageatU2240pin7.The resetgeneratorforcesU2240pin5LO,andtheLOis appliedtotheprocessorRESETinput(pin40).Afterthe SENSEinputreachesitsnominalvoltagelevel,thereset conditioncontinuestoallowthemicroprocessorsystem timetoreset.Theresetcontinuesforthetimedetermined byC2350.Theeffectofpowersupplytransientsis reducedbyC2240.Afterthesupliesreachtheirnominal levelandthedelayperiodendsU2240pin5 goesHI.The RESETsignaltotheprocessorthengoesHItoenable normalexecutionto begin,andtheprocessor isdirectedto thestartingaddressofthepower-uproutine,whichit then performs. POWERDOWNSEQUENCE.Whentheinstrument powerswitchisturnedoff,thePWRUPsignalfromJ251 pin12immediatelygoesLO.ThisLOgeneratestheNMI (non-maskableinterrupt)requestto theprocessoronpin6 whichcausestheprocessortobranchtothepower -down routine.Underdirectionofthatroutine,theprocessor beginsshuttingdowntheinstrumentinanorderlyfashion beforethepowersupplyoutputscandropbelowthe operatingthresholds.ThisroutinedisconnectstheCH 1 andCH250-0inputterminationstoprotectthemfrom accidentalapplicationofexcessivevoltageduringstorage or benchhandling. Astheoperatingvoltagesarefalling,theResetcircuitry mustnotgeneratea falseRESETsignaltotheprocessor. Sucharestartwhenthepowersupplyvoltagesareout-sidetheirnormaloperatingrangewouldproduce unpredictableprocessor operationthat couldalterthe con-tentsofthebatterybackedupRAM.Whentheprocessor hascompletedalltheotherpower-downtasks,itfinally setsthePWRDOWNsignalHIviaU2310(diagram2). ThissignalisappliedtoinverterU2650Catpin11.Pin9 ofU2650CgoesLOandimmediatelypullspin2ofReset GeneratorU2240LOtopreventa resettotheprocessor. 3-6 ResetGeneratorU2240immediatelyswitchesstateto asserttheRESETsignaltotheprocessor.TheRESET signalisheldLOuntilthepowersupplieshavefully discharged. Fordiagnosticpurposes,thePWRDOWNresetsignal canbedisabled.MovingjumperP503totheDIAG(diag-nostiC)pOSitionkeepsU2240pin2HI.TheRESETsignal isthereforeheldHI,andtheprocessorcanexecutea free-runningNOP(nooperation)loop withoutinterruptionif thePWRDOWNbitissetHIwhiletheAddressBusis incrementing. DataBus Tri-statebufferU2350isusedtobufferthedatasignals totheMicroprocessorfromotherdevicesonthebus. Whennotenabled,thedeviceisswitchedtoisolatethe processorfromthebufferedDataBus.BufferU2350is enabledviatheRead-WriteLatchU2440Bwhenthepro-cessor readsdata fromanotherdevice onthebus. Whentheprocessorwritesdataontothebus,Octal LatchU2450isenabledbytheRead-WriteLatchU2440B. WhentheE (enable)signalatpin11ofU2450isHI,pro-cessordatabitsarepassedasynchronouslythroughthe latchto thebuffereddatabus.WhentheE signalgoesLO, databitsmeetingsetuptimesarelatchedintothedevice. ThelatchedQoutputsprovidetherequireddrivecurrent tothevariousdevicesonthebusandensurethatdata holdtimesaremetforcorrectdatatransfer.Whenthe Read-WriteLatchplacesaHIonpin1ofU2450,latch U2450isdisabled,andtheoutputsareswitchedtotheir high-impedancestate. Datatransferstoandfromtheprocessormaybeinter-ruptedbyremovingDiag/NormJumperP503.Thisforcesa NOP(nooperation)conditionthatisusefulfor verifyingthe functionalityoftheprocessor(whenadata-busdeviceis suspectedof causinga systemfailure)or fortroubleshoot-ingtheAddressBusandAddressDecodecircuitry. Removingthejumperremovestheoperatingpowerfrom bothU2350andU2450todisconnecttheMicroprocessor fromthebufferedDataBus.WiththeDataBusdiscon-nected,aresistornetworkpullstheprocessorDataBus lines(DOthrough07)toaNOP(nooperation)instruction. ANOPcausestheMicroprocessortocontinuouslyincre-mentthroughitsaddressfield.TheAddressDecodecir-cuitrymaythenbecheckedtodetermineifitisoperating properly. Address Decode TheAddressDecodecircuitrygeneratesenablingsig-nalsandstrobesthatallowtheMicroprocessortocontrol Theory of Operation-2465B/2467B Service thevariousdevicesandcircuitfunctions.Thecontrolling signalsaregeneratedasaresultoftheMicroprocessor placingspecificaddressesontheAddressBus.Figure3-2 illustratestheenablesandstrobesgeneratedbythe AddressDecodecircuitry. bitA15HI)selectoneoftworead-onlymemories(ROM), U2160,orU2260.WhentheVMA (ValidMemoryAddress) andE (Enable)outputsfromtheMicroprocessor goHI,the selectedROMisenabled,andthedatafromtheselected addresslocationisreadfromtheROM. Addressdecodingisperformedbya programablearray logicdevice,athree-line-to-eight-linedecoder,andafour-line-to-sixteen-linedecoderattachedtotheAddressBus. Thefivemostsignificantaddressbitsaredecodedby U2250.Thisdeviceinitiallyseparatesthetotal addressable-memoryspace(64K-bytes)intothirty-two, 2K-byteblocks.Addressesinthetop32K-bytes(address Theprogrammablearraylogicdevicealsogenerates theOEandWEsignalstotherandom-accessmemory (RAM).ThisRAMcanbeaccessedwithaddresses8000 to9FFFifeitherPBO,PB1,orPB2signalsareHI.Inthi ....modeROMS,U2160andU2260arenotaccessibleinthis addressrange. HEXDECODEDBY ADDRESSU2250 0000 07FF 0800 OFFF 1000 7FFF 8000 FFFF RAM-U2460 ADDRESS DECODING (U2550) RESERVED FOROPTIONS ROMS-U2160 ANDU2260 RAM-U2460 \ --\ \ \ \ \ \ \ \ \ \ HEX ADDRESS 0800 083F 0840 087F 0880 08BF 08CO 08FF 0900 093F 0940 097F 0980 09CO 09FF OAOO OBFF OCOO \ODFF \OEOO ,OFFF DAC DECODEDBY U2550 DMUX2OFF MSBCLK(087F) DACLSBCLK(0880) PORT1CLK(08CO) ROS1CLK(0900) ROS2CLK(0940) PORT2CLK(0980) FURTHERADDRESS DECODING(U2660) OVERLAYOF 0800-09FF OVERLAYOF 0800-09FF OVERLAYOF 0800-09FF / / / / / \ \ \ \ \ \ \ Figure 3-2.Address decoding. HEX ADDRESS r--/09CO / 09C1 / / 09C2 / 09C3 09C4 09C5 09C6 09C7 09C8 09C9 09CA 09CB 09CC 09CD \ 09CE \ \ 09CF \ 0900 \ 09DF 09EO \09EF \09FO ,09FF DECODEDBY U2660 DMUX2ON DMUXOOFF DMUXOON PORT3IN DMUX1OFF DMUX1ON LEDCLK DISPSEQCLK ATNCLK CH2PACLK CH1PACLK BSWPCLK A SWPCLK BTRIGCLK A TRIGCLK TRIGSTATSTRB OVERLAYOF09CO-09CF OVERLAYOF09CO-09CF OVERLAYOF09CO-09CF 6019-09 3-7 Theory of Operation-2465B/2467B Service Ofthebottom32K-bytesofaddresses,onlythelowest 4K-bytesarefurtherdecoded.Addressesinthelowest 2K-byteblockofaddresseswillcauseU2250to generate anenablesignaltotheRAM,U2460.Addressesinthe next2K-byteblockofaddresseswillenableU2550todo thenext stage of addressdecoding. ThelevelofdecodingperformedbyU2550uses addressbitsA6,A7,andA8toseparatetheaddresses withinthe2K-byteblockofaddresses0800thruOFFFinto 32groupsof64addresses.AddressbitsA9andA 10are notusedinthedecodingscheme,soeachofthese32 blocksisnotuniquelyidentified.Thisresultsinfourdupli-catesectionswithintheaddressblock,eachconsistingof eightgroupsof 64addresses.Theupperthreesectionsin theaddressspaceareneverused;therefore,decodingby U2550maybemoresimplythoughtofaseightgroupsof 64addresslocations.Addresseswithintheseeight groupsgeneratecontrolsignalstootherportionsofthe instrument. Thefinallevelofaddressdecodingisdonebyfour -line-to-sixteen-linedecoderU2660.WhenenabledbytheY7 outputofU2550,thisdecoderseparatesthehighest64-addressgroup decodedbyU2550 into16 individualcontrol signals.Inthislevelofdecoding,addressbitsA4andA5 arenotdecoded,sothatthe64possibleaddresses consistof fouroverlayedblocksof 16 addresseseach. EachofthecontrolsignalsgeneratedbytheAddress DecodeCircuitryarepresentonlyaslongasthespecific addressdefiningthatsignalispresentontheAddress Bus.However,oneoftheaddressablecontrolsignals decodedbyU2550andfiveof theaddressablecontrolsig-nalsdecodedbyU2660areusedtoeithersetorreset flip-flopsU2650A,U2650B,andU2650D.Thecontrolsig-nalsare,ineffect,latchedandremainpresenttoenable multiplexersU2521 ,U2530,(diagram2)andU170 (diagram4).Whenenabled,thesemultiplexersrouteana-logcontrolsignalsfromDAC(digital-to-analogconverter) U2101(diagram2)tothevariousanalogcontrolcircuits. Read-only Memory (ROM) TheRead-onlyMemoryconsistsofone,128K-byte ROMortwo,64K-byteROMsthatcontainoperating instructions(firmware)usedtocontrolprocessor(andthus oscilloscope)operation.AddressesfromtheMicroproces-sor thatfallwithinthetop32K-bytesof addressablespace causeoneof thetworead-onlymemoryintegratedcircuits tobeenabled.(SeeAddressDecodedescription.)Instruc-tionsarereadoutof theenabledROM(orPROM)ICfrom theaddresslocationpresentonits16addressinputpin (AOthroughA 14,PageSelect).Theeight-bitdatabyte fromtheaddressedlocationsisplacedontotheBuffered 3-8 Databus(BOOthroughBD7)tobereadbytheMicropro-cessor. Random-AccessMemory (RAM) TheRAMconsistsofintegratedcircuitU2460andpro-videstheMicroprocessorwith8K-bytesofbatterybacked uptemporarystoragespacefordatathatisdeveloped duringtheexecutionofaroutine.TheRAMisenabled wheneveranaddressinthelowest2K-byteofaddresses isplacedontheAddressBusorwheneveranaddressof 8000thru9FFFisplacedontheAddressbuswitheither PBO,PB1,orPB2setHI.WhenwritingintotheRAM,the write-enablesignal(WE)onpin27ofU2460issetLO alongwiththechipenable(CE1)signalonpin20.Atthe sametime,theoutput-enable(OE)onpin22isHItodis-abletheRAMoutputdrivers.Dataisthenwrittentothe locationaddressedbytheMicroprocessor.Ifdataistobe readfromtheRAM,theWEsignalissetHItoplacethe RAMinthereadmode,andtheOEsignalissetLOto enabletheoutputdrivers.Thisplacesthedatafromthe addressedlocationonthebufferedDataBuswhereitcan bereadbytheMicroprocessor. TheRAMalsoprovidesnon-volatilestorageforthe calibrationconstantsandthepower-downfront-panelset-tings.Whenpowerisappliedtotheinstrument,the Microprocessorreadsthecalibrationconstantsandgen-eratescontrolvoltagestosetuptheanalogcircuitry.The front-panelsettingsthatwerepresentatpower-offare recalledandtheinstrumentissettotheoperatingmode previouspoweroff. Battery Circuitry TheBatterycircuitcomposedofBT2570,R2770, CR2770,CR2370,CR2371,andC2470providesthe standbyvoltagenecessarytomaintainthecontentsofthe CMOSRAM(U2460).ThecircuitcomposedofR2530, U2620C,R2504,andR2506providesthemicroprocessor ameansofmonitoringthebatteryvoltagetodetectwhen thebatteryneedstobereplaced. Timing LogiC TheTimingLogiccircuitcomposedofU2440B,and U2540F generatestime- andmode-dependentsignalsfrom controlsignalsoutputfromtheMicroprocessor.The enable(E)signaloutputfromtheMicroprocessorisa1.25 MHzsquarewaveusedtosynchronizeoscilloscopefunc-tionsto processortiming. DataappliedtotheAddressBus,DataBus,andvari-ouscontrolsignalsareallowedtosettle(becomevalid) beforeanyoftheaddresseddevicesareenabled.Thisis accomplishedbyswitchingtheEsignalH Iashorttime aftereachprocessorcyclebegins.InverterU2540Finverts thepolarityofthedelayedenablesignalandenablesthe AddressDecodestageonlyaftertheaddressbushasset-tled. Read-WriteLatchU2440Bisusedtodelaythe processor'sread/writesignal(R/W)fromtheMicroproces-sortomeethold-timerequirementsoftheRAM.Atthe sametime,itgeneratesdelayedreadandwriteenabling signalsofbothpolaritiestomeettherequirementsof BufferU2350andLatchU2450(intheMicroprocessor DataBus)andvariousotherdevicesintheReadoutcir-cuitry (diagram7). WhenR/WgoesLOfora writecycle,Read-WriteLatch U2440Bisreset,andaoutput(pin9)isheldLO,Latch U2450isinitstransparentstateatthistime,anddata fromtheMicroprocessorisappliedasynchronouslytothe bufferedDataBus.Attheendofthewritecycle,theR/W signalgoesHI,andtheresettoU2440Bisremoved.The E signalalsogoesthroughanegativetransition,anddata ontheMicroprocessordatabuslinesislatchedinto U2450.Thenextpositivetransitionof the1.25-MHzE sig-nal(1/2E cycleafter theR/WsignalgoesHI)clockstheHI levelatU2440Bpin12(theDinput)totheaoutput,and theaoutput(pin8)goesLO.The1/2Ecycledelay betweenthetimeR/WgoesH Iandthetimethatthea outputofU2440BgoesHIkeepsLatchU2450outputson longenoughtomeetthedataholdtimefortheRAM.At theendofthatdelaytime,pin1ofU2450goesHI,and theLatchoutputsareswitchedtothehigh-impedance stateto isolateit fromthebufferedDataBus. READOUTFRAMINGANDINTERRUPTTIMING.Binary counterU2640isusedtogenerateareadout-framing clocktotheReadoutcircuitryandareal-timeinterrupt requesttotheMicroprocessorviainverterU2540E.The readout-framingclockisaregularsquare-wavesignal obtainedfromU2640pin12,14or15bydividingthe 1.25-MHzEsignalby512(29),1024(210),or2048(211). ThisclocktellsthereadoutCircuitrytoloadthenextblock (subframe)ofreadoutinformationtobedisplayed.Pin12 isfora reducedinterferemodeforTVapplications,pin14 isusedforretrofitabilityintoolder2lineinstruments,and pin15isfornewer4linereadoutinstruments.(See "Readout"descriptionforfurtherinformationconcerning alphanumericdisplay.)Thereal-timeinterruptrequest, whichoccursevery3.3ms,isobtainedfrompin2by dividingtheE signalby8192 (213). Whenthereal-timerequestoccurs,IRa(pin4of U2140)goesLO,andtheprocessorbreaksfromexecution ofitsmainlineprogram.TheMicroprocessorfirstresets BinaryCounterU2640bysettingpin19of U2301(diagram 2)HI(togeneratethereset),thenitresetspin19LOto allowthecountertostartagain.Atthistime,theMicropro-Theory of Operation-2465B/2467B Service cessorsetsanalogcontrolvoltagesandreadstrigger statusfromtheDisplaySequencer(diagram5).Whenthis iscompleted,it revertsbackto themainlineprogram. Inadditiontotheanalogcontrolandtriggerstatus updatethatoccurswitheachinterrupt,oneveryfifthinter-ruptcycle,theMicroprocessoralsoscansthefront-panel potentiometers.Everytenthinterruptcycle,scanningthe front-panelswitchesandcheckingthe50-QDCinputsfor overloadsisaddedtothepreviouslymentionedtasks.If all thetasksarenotcompletedattheendofoneinterrupt cycle,thereal-timeinterruptrequestrestartstheanalog updates,butassoonasthoseareaccomplished,the Microprocessorwillpickupwithitsadditionaltaskswhere it wasbeforetheinterruptoccurred.Thiscontinuesuntilall tasksarecompleted.Ifanypotorswitchchangesare detected,theMicroprocessorupdatestheanalogcontrol voltagesandthecontrolregisterdatatoreflectthose changespriortorevertingbacktothemainlineprogram instructions. FRONT-PANELSCANNINGand ANALOGCONTROLS TheAnalogControlcircuitry(diagram2),under Microprocessorcontrol,readsthefront-panelcontrolsand setsvariousanalogcontrolvoltagestoreflectthesefront-panelsettings.Thecalibrationconstantsdeterminedduring instrumentcalibrationandthelast"stable"front-panel setupconditionsarestoredinbatterybackedupRAM.At power-onthestoredfrontpanelinformationisusedto returntheinstrumenttoits previousstate. Hardware I/O DatatransferfromtheAnalogControlCircuitrytothe MicroprocessorisviaStatusBufferU2220.Databits appliedtotheinputpinsarebufferedontotheDataBus whenenabledbytheAddressDecodecircuitry.Viathe StatusBuffer,theprocessorisableto(1)determinethe settingsoffront- andrear-panelpotsandswitches,(2) determineinstrumenttype (2465Bor 2467B),(3)determine ifatriggeredsweepisinprogress,and(4)readthecon-tentsof theReadoutRAM.Whendisabled,thebufferout-putsareswitchedtohighimpedancestatestoisolate themfromthebufferedDataBus. DatatransferfromtheMicroprocessortotheAnalog ControlcircuitryisviaregistersU2210andU2310.Via registerU2210,theMicroprocessorisabletoselectthe 3-9 Theory of Operation-2465B/2467B Service pot-scanningmultiplexers,turnthetriggerLEDonandoff, andcontrolotherhardwareviaserialcontroldataandthe attenuatorstrobe.ViaregisterU2310,theprocessorcon-trolspotselection,ROMaddressing,andpowerdowntim-ing. Front-Panel Switch Scanning TheFront-PanelSwitchesarearrangedinamatrixof tenrowsandfivecolumns.Mostoftherow-columninter-sectionscontaina switch.Whena switchisclosed,oneof therowlinesisconnectedtooneofthecolumnlines throughadiode.Readingof theswitchesisaccomplished bysettingasinglerowlineLOandthencheckingeachof thefivecolumnlinessequentiallytodetermineifaLOis present(signifyingthataswitchisclosed).Aftereachof thefivecolumnshavebeenchecked,thecurrentrowline isresetHIandthenextrowlineissetLOforthenext columnscancycle.AcompleteFront-Panelscanconsists of alltenrowlinesLOinsequenceandperformingafive-columnscanfor eachof therows. Row linesaresetLOwhenthemicroprocessorwritesa LOtooneoftheflip-flopsinoctalregistersU2301or U2201.TherowdataplacedonthebufferedDataBusby theMicroprocessorisclockedintotheregistersastwo, eight-bitwordsbyclocksfromtheAddressDecodecir-cuitry(DACLSBCLKforthelowereightbitsandDAC MSBCLKfortheuppereightbits).Alleightoutputsof registerU2201andtwooutputsofU2301drivetheten rowsofthefront-panelswitchmatrix(thefifthlineofthe matrixisnotused).Seriesresistorsinthelineslimit currentflowandeliminatenoiseproblemsassociatedwith excessivecurrentflow. Whileeachrowisselected,theprocessorwillscan eachofthefivecolumnlinesinsequence.Toscanthe columns,theprocessorincrementsthreedataselectbits fromU2301thatdefinethecolumntobechecked.Eight-linedataselectorU2410connectstheassociatedcolumn linetoStatusBufferU2220.Aseachlineisselected,the Microprocessor readstheStatusBufferto determineif the associatedswitchisopenor closed. Inadditiontothefront-panelswitches,theCAUNO CALjumper(P501)ischeckedtodeterminewhetherthe instrumentshouldbeallowedtoexecutethecalibration routines.ThelevelsonU2410pin7and9arereadby scanningtwoadditionalcolumnsatpower-up.Ifthe jumperispullingtheCALbitLO,theoperatorwillbe allowedtousethecalibrationroutinesstoredinfirmware. If theNOCAL bitispulledLO,thecalibrationroutinesmay not beperformed.If thejumperisremoved,andneither bit ispulledLO,theMicroprocessorisforcedintoaspecial 3-10 diagnosticmode(CYCLE)usedtorecordcertainoperating failuresduringlong-termtestingoftheinstrument.(See the"Maintenance"sectionforanexplanationofthediag-nostic modes.)RemovingP501or switchingit betweenthe CALandNOCALpositionswillnotberecognizedbythe Microprocessoruntiltheinstrumentispowereddownand thenturnedbackon. TheresistorsinserieswiththeinputlinestoU2410are current-limitingresistorsthatprotecttheCMOSeight-line dataselectorfromstaticdischarges.Theresistorscon-nectedfromtheinputlinesto the+ 5Vsupplyarepull-up resistorsfor thefront-panelcolumnlines. Digital-to-Analog Converter (DAC) DACU2101isusedtosetthevariousanalogrefer-encesintheinstrumentandisusedtodeterminetheset-tingsofthefrontpanelpotentiometer.The12-bitdigital valuesto beconvertedarewrittento octalregistersU2301 andU2201for applicationto theDACinputpins.TheDAC thenoutputstwocomplementaryanalogcurrentsthatare proportionaltothedigitalinputdata.(Complementary,in thiscase,meansthatthesumofthetwooutputcurrents isalwaysequalto a fixedvalue.) Themaximumrangeoftheoutputcurrentsisestab-lishedbyavoltage-dividernetworkcomposedofR2010, R2012,R2013,andR2011conectedtothepositiveand negativereferencecurrentinputsof theDAC(pins14and 15respectively).A+ 10-V referencevoltageappliedto the DACthroughR2013setsthebasicreferencecurrent. ResistorR2011andpotentiometerR2010provide a means toadjustthiscurrentoverasmallrangeforcalibration purposes.Thenominalreferencecurrentis1 mA,theDAC full-scaleoutputcurrentis4 mAoTheoutputcurrentsflow throughseriesresistorsR2520andR2521,connectedto the+ 1.36-V reference,andproportionalvoltagesresult. Pot Scanning ThePotScanningcircuitry,inconjunctionwiththe DAC,derivesdigitalvaluesforeachofthevariousfront-panelpotentiometers.Scanningofthepotsisaccom-plishedbydataselectorsU2401,U2501,andU2601. Threebitsarewrittento registerU2310andselectthepot toberead.Thebitsarelatchedintheregisterandkeep thepotselecteduntiltheregisterisreset.TheMicropro-cessorwritesaLOtotheinhibitinputpin(pin6)of either U2401,U2501orU2601viaregisterU2210toenablethe device.Theenableddataselectorconnectstheanalog voltageatthewiperoftheselectedpottocomparator U2510. ComparatorU2510comparestheanalogvoltageof eachpottotheoutputvoltagefromtheDAC(pin18).To determinethepotentiometeroutputvoltage,theprocessor performsabinarysearchroutinethatchangestheoutput voltagefromtheDACinanorderlyfashionuntilitmost closelyapproximatesthevoltagefromthepot. Theconversionalgorithmissimilartosuccessive approximationandgeneratesaneight-bitrepresentationof theanaloglevel.Whenthepot'svalueisdetermined,the Microprocessorstoresthatvalueinmemory.Onceallof thepotshavebeenreadandtheinitialvalueof eachhas beenstored,theprocessor usesa shorter routineto deter-mineifanypotsettingchanges.TodothistheDACout-putissettothelastknownvalueofthepot(plusand minusa smalldriftvalue),andthestatusbitisreadto see thata HIandLOoccurs.Ifwithinthelimits,theprocessor assumesthatthepotsettinghasnotchangedandscans thenextpot.Whentheprocessordetectsthatapotset-tinghaschanged,itdoesanotherbinarysearchroutineto findthenewvalueof thatpot. AnalogControl Theoperatingmodeandstatusoftheinstrument requiresthatvariousanalogvoltages(for controllinginstru-mentfunctions)besetandupdated.Thedigitalvaluesof thecontrollingvoltagesaregeneratedbytheMicroproces-sorandconvertedbytheDAC.AnalogmultiplexersU2521 andU2530(ondiagram2)andU170(ondiagram4)route theDACvoltagestocircuitsthatmaintain the controlvoltagesbetweenupdates. TheMicroprocessorwritesthreeselectionbitstoregis-terU2301thatdirectstheDACoutputtotheappropriate sample-and-holdcircuitandchargesa capaCitor(or capac-itors)tothelevelof theDAC.Whentheprocessordiscon-nectstheDACvoltagefromthesample-and-holdcircuit (bydisablingthemultiplexer)thecapacitor(s)remains chargedandholdsthecontrolvoltagenear thelevelsetby theDAC.Duetotheextremelyhighinputimpedanceof theassociatedoperationalamplifiers,thechargeonthe capacitor(s)remainsnearlyconstantbetweenupdates. FRONT-PANELCONTROLS TheFrontPanelistheoperator'sinterfaceforcontrol-lingtheuser-selectableoscilloscopefunctions.Alongwith thecrt,itprovidesvisualfeedbacktotheuseraboutthe presentoperatingstate of theinstrument. TheoryofOperation-2465B/2467B Service MostoftheFront-Panelcontrols(diagram3)are"cold" controls;i.e.,theyarenotconnecteddirectlyintothesig-nalpath.Therefore,associatedcircuitsarenotinfluenced bythephysicalparameters(suchascapacitance,resis-tance,andinductance)ofthecontrols.Inaddition, translatingtheanalogoutputlevelsofmostofthepoten-tiometerstodigitalequivalentsallowstheprocessorto handlethedatainwaysthatresultinavarietyof enhancedcontrolfeatures. Tomaintainthefront-paneloperatingsetupbetween usesoftheinstrument,thedigitizedvaluesofthepoten-tiometersandfront-panelswitchsettingsarestoredinbat-terybackedupRAMsothatwhentheinstrumentpower is turnedoff,thesecontrolsettingsarenotlost.Then,when powerisnextapplied,theinstrumentwillpoweruptothe sameconfigurationaswhenthepowerwaslastremoved (assumingthesettingsofthenon-digitizedpotsand switchesremainthesame). TheFront-PanelControlsalsoallowtheusertoinitiate anddirectthediagnosticroutines(andwhenenabled,the calibrationroutines)programmedintotheread-only memory(ROM).Theseroutinesareexplainedinthe Maintenancesectionof thismanual. Front-PanelSwitches TheFrontPanelSwitchesarearrangedinaten-row-by-five-columnmatrix,witheachswitchassignedaunique locationwithinthematrix(seeFigure3-3).A closedswitch connectsarowandacolumntogetherthroughanisolat-ingdiode.Todetecta switchclosure,theswitchmatrixis scannedonceevery32ms(everytenthMicroprocessor interruptcycle).Whenscanning,theMicroprocessor seqLientiallysetseachindividualrowlineLO.Aclosed switchenablestheLOtobepassedthroughtheassoci-ateddiodetoacolumnline.Whentheprocessorchecks eachof thefivecolumnlinesassociatedwiththeselected row,theLOcolumnisdetected.Theintersectionofthe selectedrowandthedetectedcolumnuniquelyidentifies theswitchthatisclosed.Furtherinformationaboutswitch scanningisfoundinthe"Front-PanelScanning"descrip-tionlocatedinthe"AnalogControl"discussion. Aseachswitchisread,theprocessorcomparesthe presentstateoftheswitchtoitslast-knownstate(stored inmemory)and,ifthesame,advancestocheckthenext switch.Whena switchisdetectedashavingchanged,the processor immediatelyreconfiguresthesetupconditionsto reflectthemodechangeandstoresthenewstateofthe switchinmemory.Thedetectedstatusoftheswitchon eachof thefollowingscancyclesisthencomparedagainst thenewstoreddatatodetermineiftheswitchchanges 3-11 Theory of Operation-24658/24678 Service again.The32-msdelaybetweenthetimeaswitchis detectedashavingchangedandthenexttimeitisread effectivelyeliminatestheeffectsofswitchingnoise(switch bounce)thatmayoccurafter theswitchisactuated. Front-PanelPots ThethirteenFront-PanelPotentiometers,READOUT INTENSITY,andINTENSITYare"cold"controlsthatcon-trolthelinearfunctionsof theinstrument.(SCALEILLUM andFOCUSarenotconsideredpartoftheFront-Panel Controlcircuitryforthepurposesofthisdescription.)All aredigitizedandcontroltheirfunctionsindirectly.Data SelectorsU2401,U2501,andU2601intheAnalogControl circuitry(diagram2)routethewiperarmvoltageof thepot FROMDATA LATCHESU2301 ANDU2201 ROW0 r------SWITCHMATRIX* beingreadtocomparatorU2510whereitiscompared withtheoutputofDACU2101.Theprocessorchanges theDACoutputuntilitmostcloselymatchestheoutput voltageofthepot.thenstoresthedigitalvalueofthe "match".Seethe"PotScanning"descriptioninthe" Ana-logControl"discussionforfurtherinformationontheread-ingof potvalues. Liketheswitchmatrixscanning,theFront-Panelpot scanningroutineisperformedevery16ms.Whenentered, theroutinereadsthesettingsofthe"last-moved"potand one"unmoved"pot.Eachsucceedingscancontinuesto readthelast-movedpot inadditiontoa newunmovedpot. Inthisway,eachpotismonitored,butmostofthescan timeisdevotedtothepotthatisstillmoving(needingcon-tinuousupdating). ----------, L_________________ ~ NOTE:NOTALLMATRIXPOSITIONSAREUSED 6019-05 Figure 3-3.Front-panelswitch matrix. 3-12 Astheinitialpotsettingsaredetermined,adigital representationof eachvalueisstoredinmemory.Thepro-cessorthencheckseachpotagainstitslast-knownvalue todetermineifapothasmoved.Ifapotisdetectedas moving,theprocessorexecutesaroutinethatconverts themovement(displacementfromlast-setvalue)intoa correspondingcontrolvoltage. Whenproducingtheactualanalogcontrollevels,the processorcanmanipulatethedigitalvaluesreadforthe variouspotsbeforesendingtheoutputdatatotheDAC. Thisallowsmanyof theoscilloscopeparametersto varyin anenhancedfashion.Thepotdataismanipulatedbythe processorinamannerthatproducessuchfeaturesas variableresolution,continuousrotation,fine-resolution backlash,andelectricallydetentedcontrols. WithallthirteenFront-PanelPotentiometers,READOUT INTENSITY,andINTENSITYcontrols,theprocessor reads themagnitudeanddirectionofpotrotationandproduces variable-resolutioncontrolvoltages.Ifapot'sdirectionof rotationchanges,themagnitudeofthechangefromthe last-setpositionremainssmall,or if itwasnotthelastpot moved,afine-resolutioncontrolvoltageresults.Inthe fine-resolutionrange,agivenrotationdisplacementwill causeasmallcontrolvoltagechange.Thesamedisplace-mentfartherawayfromthelast-setreferencewillcausea proportionallylargercontrolvoltagechange,producinga coarse-resolutioneffect.Ifthechangingpotisthelast one movedandthedirectionof rotationremainsthesame,the algorithmcontinuesfromwhereitleftoffduringthe precedingscan;producingcontrolvoltagechangeswith thesameincrementasitwaslastusing. Thedeltareferencecontrols( ~REFORDLYPOSand ~ )arecontinuous-rotationpotentiometers.Theyeachcon-sistoftwopotsgangedtogetherwiththeirwiperarms electricallyorientedat1800apart.Asthewiper of onepot isleavingitsresistiveelement,thewiperoftheotherpot comesontoitselement.TheMicroprocessorhastheabil-itytowatchtheoutputvoltagefromeachwiperandwhen itdetectsthatthecontrollingwiperisnearingtheendof itsrange,itwillswitchcontroloverto theotherwiper.The routinetheprocessorusestowatchthesepotssetsthe associatedcontrolvoltageonthebasisofrelativevoltage changes( ~ V )thatoccur.Switchingbetweenthepotsto changecontroltotheoppositewiperarmisbasedon specific voltagelevelsbeingsensed. Sensingspecificvoltagelevelsisalsousedwhenread-ingtheVOL TS/DIVVAR,SEC/DIVVAR,andHOLDOFF controls.Thesepotshavebotha mechanicaldetentanda processor-generatedelectricaldetent.Asoneofthese controlsismovedoutofthemechanicaldetentposition, Theoryof Operation-2465B/2467B Service theprocessorwatchestheanalogvoltagechangesthat occur;buttheassociatedcontrolvoltagewillnotchange untilaspecificvoltagelevel(theelectricaldetentlevel)is reached.Oncetheelectricaldetentvalueisexceeded,the processorbeginstovarytheassociatedcontrolvoltagein responsetofurtherpotrotation.Whenreturningtothe mechanicalposition,theelectricaldetentlevelisreached first,andthevariablevoltageactionisstoppedbeforethe mechanicaldetentisentered. Front-Panel Status LEOs Light-emittingdiodes(LEOs)areusedtoprovidevisual feedbacktotheoperatorabouttheoscilloscopestatus andoperatingmodebybacklightingfront-panelnomencla-ture.A48-bitstatusword,definingthediodestobe illuminated,isgeneratedbytheprocessor andthenserially clockedintothesixLED-StatusRegisters(U3001,U3002, U3003,U3004,U3005,andU3006).Theregistersholdthe selecteddiodesonuntilthenextupdate.Wheneverthe processordetectsthatafront-panelcontrolhaschanged (andanewstatusdisplayisrequired),anewstatusword isgeneratedandappliedtopin1 of U3002.Aseachof the bitsisclockedintotheQA positionofU3002,thepreced-ingbitisshiftedtothenextregisterposition.After48bits ha