IBM 2671 User manual

FileNumberS360/S370-08
OrderNo.GA24-3388-5
SystemsReferenceLibrary
mtsmsi
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IBM 2671PaperTapeReader
IBM 2822 Paper TapeReaderControl
ComponentDescription
i
ThispublicationgivessufficientinformationtounderstandtheIBM
2671PaperTapeReaderandIBM2822PaperTapeReaderControl
andtheassociatedspecialfeatures.Themainpurposeofthepublication,
however,istoassistprogrammersandoperatorstooperatethemachine
whenitisusedasan I/O unittotheIBMSystem/360Model25, 30,40,
44, 50,or67,ortoSystem/370.Therelevanceofthecontrolsand
indicatorsforsucha configurationaregiven,togetherwithpointsof
specificinteresttothefollowing:
•Programmers:Operationalcharacteristics,includingstopconditions,
addressing,recoveryprocedures,andSystem/360commands.
•Operators:Tapeloading,unloading,rewinding,andrepairprocedures.
•SystemAnalysts:Tapespecifications.
Thesectionsforprogrammerspresupposea knowledgeofSystem/360
andSystem/370operationandofpapertapereaders,butnosuch
knowledgeisrequiredinunderstandingthesectionsforoperators.
Associated Publications
PhysicalCharacteristicsofthe 2671 PaperTapeReaderand2822Paper
TapeReaderControlandofSystem/360operationaregiveninthe
followingpublications:
1. IBM System/360 Installation Manual — Physical Planning, OrderNo.
GC22-6820.
2. IBM System/360 Installation Manual - Physical Planning, IBM World
Trade 50-Hertz Requirements, OrderNo.GC19-0001.

Preface
Thispublicationiswrittenforcustomerprogrammersand
operatorsusingtheIBM 2671 PaperTapeReaderand
IBM2822PaperTapeControlasan I/O unittoanIBM
System/360Model25,30, 40,44, 50,or67,ortoan
IBMSystem/370.Programmersshouldbefamiliarwiththe
System/360,butoperatorsrequirenopreviousexperience
ofSystem/360orthemachineoperationtousethispubli-
cation;descriptionsinthispublicationassumethatthe
2671/2822isattachedtoSystem/370viaa singlemulti-
plexerchannel,inwhichcaseoperationisidenticalto
System/360operation.
Thepublicationdescribesingeneraltermstheoperation
ofthe 2671/2822 andassociatedfeaturesin"Introduction",
andgivestherelevanceofthecontrolsandindicatorswith
System/360operationin"2671ControlsandLamps".
Programmersshouldread"OperationalCharacteristics",
inwhichdatahandlingdetailsaregiven.Operatorsshould
followtheinstructionsgivenin"PaperTapeSplicing",
"CleaningbyOperator",and"TapeLoading,Unloading,
andRewinding".
Becausetherearefivepossibleconfigurationsofthe2671,
theloadinginstructionshavebeendividedintobasiclogical
steps, eachstepbeinggivenona separatetabulatedpage.
Thislayoutallowsoperatorstoselectandcollatetheinstruc-
tionsparticulartotheirmachineconfiguration.
Fordetailsofthetapethatcanbereadbythe2671/2822
see"PaperTapeSpecifications".
Sixth Edition (July1973)
ThisisareprintofGA24-3388-4incorporatingchangesreleasedinTechnicalNewsletter
GN33-0004(datedFebruary 18, 1972).
Changesareperiodicallymadetotheinformationherein;anysuchchangeswillbereported
insubsequentrevisionsorTechnicalNewsletters.
Requestsforcopiesof IBM publicationsshouldbemadetoyourIBMrepresentativeorto
theIBMbranchofficeservingyourlocality.
Aformforreaders'commentsisprovidedatthebackofthis publication. Iftheformhas
beenremoved,addressyourcommentstoIBMFrance,Centre d'Etudes etRecherches,
ProductPubhcations,Dept.0762, 06610 LaGaude,France.
©CopyrightInternationalBusinessMachinesCorporation1965,1966,1971.

Contents
Introduction. ....1
Basic 2671 PaperTapeReader1
ReadHead1
ReaderDrive2
ReaderBrake2
End-of-TapeSensor2
SpecificationofTapeBasket2
SpecialFeaturesfor 2671 2
SupplyFeature2
Center-RollFeature2
Take-UpFeature3
2822PaperTapeReaderControl3
BufferandDataRegister3
DeleteCharacterDetection3
ChannelInterface3
IsolationFeature3
2671ControlsandLamps5
2671ConsoleSwitches5
End-of-RecordSwitches5
DeleteSwitch5
TrackSuppressSwitch5
ParitySwitch6
2671ConsolePushbuttons'6
Power-On-and-ResetPushbutton6
Power-Off-if-in-Local Pushbutton6
StartPushbutton6
StopPushbutton6
End-of-File Pushbutton6
NPRO(NonprocessRunout)Pushbutton6
Step-by-StepPushbutton7
2671ConsoleLamps7
Power-On-and-ResetLamp7
ReadyLamp7
End-of-FileLamp7
EquipmentCheckLamp7
DataCheckLamp7
NPRO Lamp7
OverstepLamp7
LoadLamp7
Off-LineLamp7
HoursCounter8
2671ReaderPlateSwitches8
Load Switch 8
SupplySwitch8
RotatingTab8
Tape-WidthSelector9
TurntableKey9
OperationalCharacteristics1
Interface1
InterfaceTiming1
Addressing1
Commands1
StatusBytes12
ExamplesofStatusBytes12
SenseBytes13
ExamplesofSenseBytes13
TapeCodeTranslation14
SpecialTapeCodeCharacters14
NormalStopConditions 14
CharacterCountEqualsZeroorEORCharacter14
CharacterCountEqualsZero14
EndofRecord(EOR)Detection15
SupplyStackerStop15
End-of-TapeCondition 15
ChannelContention15
DataCheck15
AbnormalStopConditions17
OperatorIntervention17
WithoutOperatorIntervention17
ErrorRecoveryProcedures17
EquipmentCheck17
InterventionRequired17
DataCheck17
PaperTapeSpecifications19
PaperTapeDetails19
Dimensions19
FeedHoles19
Chad20
PaperTapeHandling20
PaperTapeSplicing.21
OverlapSplice21
Butt-Joint Splice21
SplicedTapeSpecification22
CleaningbyOperator. 23
CleaningSupplyandTake-UpStackers23
CleaningReadHead23
TapeLoading,Unloading,andRewinding25
LoadingInstructions26
Step1:Preparingthe 2671 forLoading29
Step2:LoadingReelsontoSupplyFeature31
Step 3: LoadingReelsontoCenter-RollFeature33
Step4:LoadingSupplyStacker35
Step5:SettingtheRotatingTab37
Step 6: LoadingTapeintoReadHead39
Step7:PositioningtheTapeBasket41
Step8:LoadingTapeontoTake-UpFeature43
Step9:Reading(RemotePowering)45
Step10:Reading(LocalPowering)45
UnloadingInstructions47
UnloadingReadHead47
UnloadingtheTake-UpFeature47
PowerOff(IfinLocalMode)47
RewindingInstructions47
AbbreviationsandGlossary49
Index51

Illustrations
Frontis-IBM2671PaperTapeReaderandIBM2822Paper
pieceTapeReaderControl '-
1ConnectiontoSystem/3601
2Basic2671andSpecialFeatures1
32822BlockSchematic3
42671PaperTapeReader:Console5
5 2671PaperTapeReader:ReaderPlate8
6TapeSpecifications19
7OverlapSplice21
8 Butt-Joint Splice21
9TapePathCleaning23
10TapeLoadingFlowchart26
11IdentificationoftheTapeLoadingSteps....27
12Step1:Preparingthe2671forLoading29
13Step2:LoadingReelsontoSupplyFeature
(Clockwise-WoundReel Shown) 31
14Center-RollFeature:IdentificationofClockwise-
WoundandCounterclockwise-WoundTape. . . .33
15Step3:LoadingReelsontoCenter-RollFeature. . 33
16Step4:LoadingSupplyStacker35
17Step5:SettingtheRotatingTab37
18Step6:LoadingTapeintoReadHead39
19Step8:LoadingTapeontoTake-UpFeature...43
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Frontispiece.IBM 2671 PaperTapeReaderandIBM2822PaperTapeReaderControl[01769]

Introduction
TheIBM2671PaperTapeReader(seeFrontispiece)reads
5-, 6-,7-, and8-trackpunchedchadpapertapes at speeds
between500 and1,000characterspersecond.Thecharac-
tersreadarebufferedoneata timebytheIBM2822Paper
TapeReaderControl and transmitted toan IBM
System/360over one of the System/360multiplexer or
selectorchannels.
The 2671/2822 maybeconnected to any of thefollow-
ingmodelsofSystem/360: 25,30,40,44, 50,or67.
The2671 is controlledbythe2822,whichreceivesallits
commands via one of theSystem/360channelsfrom the
System/360(Figure 1).
The2671/2822 can equally be attached to System/370
through a simplemultiplexerchannel.Theoperationinthis
instance is identical to the operationwithSystem/360.
Therefore,referencesmadethroughoutthispublication to
System/360alsomeanSystem/370.
Allpapertapecodes,exceptSystem/360code,require
translationbeforethecharactersofthecodetakeonmean-
ing.Translationisdonebymeansof a look-uptableheldin
theSystem/360program. The characterstransmitted are
heldbytheSystem/360 in theiroriginalcodeandareonly
translatedwhenthetapeorrecordisended.
BASIC2671PAPERTAPEREADER
Thebasic 2671 (Figure2) canreadstripsofpunchedpaper
tape, whoselengthsmayrangefrom9 inches(in.)(23centi-
meters [cm]) to20 feet (ft)(6,1 meters[m]).These
lengthsinclude a 6-inch (15,2 cm)longleaderanda 3-inch
(7,6 cm) longtrailer.Tapesthathavecompletelyblank
sections(withoutfeedholesalso)cannotberead.
Thebasic 2671 comprises:
1. Readhead.
2. Readerdrive.
3. Readerbrake.
4. End-of-tapesensor.
ReadHead
Thepapertape is constrained by tapeguides to pass
between a lightsource andten photocells(eightreading
2671
**
2822
Data
Controls
^
System/360
Channel System/360
Figure1. Connection toSystem/360[08269]
,102822
Raadv
Driw
^]
T.n U
Photocells
Retractable^ \
Reactor .„
fBrake ~| pE"*^'
=n^_
x Photocells x
Take-Up Feature
.Light
ISource |
tarfc267T iiiiiiiiipiii^iiiiiipii
Figure2.Basic2671andSpecialFeatures [01770A]
Introduction 1

photocells,feedholephotocell,andlightsourcecontrol
photocell).Thetapeguidesmayberetractedbytheopera-
tortoinsertpapertapeintothereadhead.A tape-width
selectorallowsthetapeguidestobecorrectlysetfor5-,6-,
7-, and8-trackpapertapes.A readingphotocellisposi-
tionedateachtrackofthepapertape.Thetracksarenum-
beredfrom1 through8,workingfrombottomtotopof
thereadhead.
Ifa holeispunchedina trackofthepaper tape, suffi-
cientlightpassesthroughtheholetooperatethetrack
photocell.Ifnoholeispunched,insufficientlightpasses
throughthepapertooperatethephotocell.
Theoutputsofalleightreadingphotocellspasstothe
2822.
FeedHole Photocell
Thefeedholephotocelldetectsthefeedholesinthetape.
Thephotocelloutputisusedtocontrolthefeedingoftape
intothesupplystacker(ifthesupplyfeatureisequipped),
andtostopthereaderdriveifnofeedholesaredetectedin
asectionoftape.
Light Source Control Photocell
Thisphotocellisusedtocontroltheintensityofthelight
source.Thephotocellispositionedbetweentrackssothat
variationsinthelightpassingthroughthepaperare
detected(duetochangesinpaperthickness,forexample).
Theoutputofthephotocellisusedtocontrolthelight
sourcesupply,sothatthedifferenceinlightintensity
betweenholeandno-holeconditionsmaybeheldconstant.
ReaderDrive
Thereaderdrivemotoroperatescontinuouslyafterpower-
on.Thereaderdriveclutchiscontrolledfromthe2822,
andwhentheclutchengagestheidlerroller,thepapertape
isdrawnthroughthe2671ata maximumspeedof1,000
characterspersecond.Whentheend-of-tapesensoroper-
ates, a signalissenttothereaderdriveclutchcontrollogic
todisengagetheclutch,independentlyofthe2822.
ReaderBrake
Thereaderbrakehastwobrakingsurfaces.Thebrakingsur-
facesareforcedtogetherbyanelectromagnet,controlled
bythe2822.Theefficiencyofthebrakingactionissuch
thatthetapestopsonthenextcharactertoberead,regard-
lessofthespeedofthetape.
Note: Thereaderdriveandthereaderbrakearecontrolled
sothatwhenthereaderdriveisengagedthereaderbrakeis
released,andviceversa.
End-of-TapeSensor
Thepapertapepassesoverthefeelerofa microswitch,
whichistheend-of-tapesensor.Assoonasthereisnotape
inthesensor,themicroswitchoperates.Themicroswitch
contactsarewiredtothereaderdriveclutchsothatthe
clutchisdisengagedwhenthemicroswitchoperates.
Specification ofTapeBasket
Toavoidtapefrombeingspilledontothefloorifthetake-
upfeatureisnotfitted,thecustomerisadvisedtohave
madea basketofthefollowingdimensions:
Height:39in.(99cm)
Length:20in. (51 cm)
Width: 24in.(61cm)
Thebasketshouldbemadeofwoodorcardboard,but
notofmetal.Metalbasketscauseelectrostaticdischarges
whichcaninterferewiththeoperationofthe2671/2822,
andalsootherunitsnearby.
TapebasketsarenotavailablefromIBM.
SPECIALFEATURESFOR2671
Inordertoreadreelsofpunchedpapertapeandtoreelthe
tapeafterreading,thefollowingspecialfeaturescanbe
supplied:
1. Supply(reel-feeding)feature.
2. Center-rollfeature.
3. Take-upfeature.
Thesupplyfeatureisa prerequisiteforthecenter-roll
feature.
SupplyFeature
Thesupplyfeature(seeFigure2)feedspunchedpaperfrom
areelintothesupplystacker.Thetapeisdrawnoutofthe
stackerbythereaderdrive.Thetapeisreeledofftokeep
thestackerfullatalltimes;thesupplymotoriscontrolled
byphotocellslocatedinthestacker.
Thereelmaybewoundclockwiseorcounterclockwise,
butisalwaysreeledofftheoutsideofthespool.Thetape
reelalwaysneedstoberewoundbeforeitisusedagain.
Themaximumsupplyspeedintothestackeris500
characterspersecond.
Theinsideofthediameterofthereelmaybe4-1/2in.
(12 cm)or2 in.(5cm);thefeaturehasbothtypesofhub.
Theoutsidediameterofthehubmustnotexceed10.5in.
(27cm).
Ifthereelistobewoundontothetake-upfeature,then:
1. Totaltypelengthmustnotexceed1,000ft(305m).
2. Tapeleadermustbeatleast20in. (51 cm)long.
Forstripfeeding,theleadermustbeatleast6 in. (15 cm)
long.
Foralltypesofuse,thetapetrailermustbeatleast3 in.
(8cm)long.
Center-RollFeature
Thesupplyfeatureisa prerequisiteforthecenter-roll
feature.
Thetapeispulledfromtheinsideofthespoolbymeans

ofa specialcenter-rollfeedingdevice.Thetapeisfedinto
thestackerasforthesupplyfeature.Thereelmaybeeither
woundclockwiseorcounterclockwise.
Center-rollfeedingremovesthenecessityforrewinding
thereeloftapeattheendofa readoperationifthetake-up
featureisfitted.
Reelswithinsidediametersoffrom2-3/4in.to4-1/2in.
(7cmto 11,4 cm)canbeused.Thelengthoftapemust
notexceed1,000ft(305m);thisgives,forexample,an
outsidediameterof10-1/2in.(27cm)toa reelwiththe
maximuminsidediameter.
Take-Up Feature
Thetake-upreel(seeFigure2) windsintapefromthe
take-upstackerata speedof500 characterspersecond.As
soonastapeisfedintothetake-upstackerbythereader
drive,thepresenceofthetapeissensedbya photocell,
whichswitchesonthetake-upmotor.Whenthetake-up
stackerempties,thetake-upmotorstops.
2822PAPERTAPEREADERCONTROL
The2822containslogicthatmatchesthe2671tothe
System/360channel.Themoreimportantpartsofthelogic
areshownonFigure3.
BufferandDataRegister
Theoutputsofthephotocellsinthereadheadarefedtoa
buffer.Thebufferholdsthecharacterjustreadonthetape,
anda dataregisterholdsthepreviouscharacterwaitingto
betransmittedtotheSystem/360;theSystem/360must
acceptthedatafromthedataregisterwithin0.8milli-
seconds.Whenthedataregisterisemptied,itisreloaded
fromthebuffer,whichisthenfreetoacceptanother
characterfromtape.Ifthecharacterinthedataregisteris
notacceptedwithinthe0.8millisecondperiod,the2671
stopsimmediatelyonthecharacternotyetread.Sucha
stoppageiscalledchannel contention.
DeleteCharacter Detection
Thedeletecharacterdetectionlogicrecognizescharacters
havingeveryavailabletrackpunched,includingthefeed
hole. Thedeletecharacterresetsthebuffer,whichisleft
emptytoreceivethenextvalidcharacteratthereadhead.
ChannelInterface
The2822convertschannelcommandsfromSystem/360in-
tocontrolsforthe2671.The2822alsotransmitsdatachar-
acters, statusbytes,andsensebytestoSystem/360.The
interfacepresentedisthestandard I/O System/360channel
interface.
IsolationFeature
Theisolationfeatureisinstalledonallmachinesof
engineeringchangelevel 351 649,andcanbefittedasa
specialfeaturetoallmachinesbelowthisengineering
changelevel.
TheisolationfeatureallowstheIBMcustomerengineerto
switchonandoffthe2671readily,withoutdisturbingthe
operationoftherestoftheSystem/360.
Thefeatureisbuiltintothepowercontrolcircuitsand
thestandard I/O channelinterfaceofthe2822.The
circuitry,whichpreventsdisturbancetotherestofthe
systemwhenswitchingonandswitchingoffthe2671,is
calledthedegatelogic.Thedegatelogiccanbemadeoper-
ativebya degateswitch,locatedinthe2822.Thedegate
logiccontrolsthepower-onandpower-offsequences,ensur-
ingthatall2671operationshaveceasedbeforeswitch-off
2671
ReadHead
2822
Buffer
Delete
Detection
Internal
Circuits
Controls
Data
Register
Control
Logic
Figure3.2822BlockSchematic[08270]
Channel
Interface
-System/360Channel
Data
Commands
Introduction3

andthatno2671operationcantakeplaceduring
switch-on.
Whenthedegateswitchissetoff,interlocksareprovided
tostopthepowerbeingturnedonandofflocally.The
power-on-and-resetpushbutton,however,retainsthereader
resetfunction,evenwhenthepower-onfunctionis
inhibited.Thepower-off-if-in-localpushbuttonlosesits
functioncompletely.

2671ControlsandLamps
Thepositionsoftheswitches,pushbuttonsandlampson
theconsoleofthe 2671 areshowninFigure4.
2671CONSOLESWITCHES
Allswitchesareactivewhenpushedup.
End-of-Record Switches
Theend-of-record(EOR)character,whenread,meansthat
therecordthathasjustbeenreadisfinished.
Anycharacterleftspareinthetapecodemaybeusedas
theEORcharacter.ThecodeoftheselectedEORcharacter
mustbesetupontheend-of-recordswitches,sothatthe
2671 canbestoppedwhentheEORcharacterisread.The
up-positions oftheend-of-recordswitches,bytrack,corre-
spondtoonesandthedown-positionscorrespondtozeros
inthetapecode.
DeleteSwitch
Thedeletecharacteristhatcharacterhavingallavailable
trackspunched,includingthefeedhole.Whenthedelete
switchispushedup,alldeletecharactersreadareauto-
maticallysuppressedinthe2822andarenottransmittedto
System/360.
Whenthedeleteswitchispusheddown,thedeletecharac-
teristransmittedtoSystem/360,justlikeallother
characters.
Ifreadingona trackissuppressedforanyreason(thisis
notapplicabletotrack8),thedeletecharacterisnotrecog-
nizedassuchandistransmittedtoSystem/360,evenwhen
thedeleteswitchison.
TrackSuppressSwitch
Whenthetrack-suppressswitchispushedup,readingona
track(from1 to7)chosenbythecustomerissuppressed.
Thebitofthecodecorrespondingtothesuppressedtrackis
madezero.Thetapecodeparityisautomaticallyadjusted
inthe2822.
Whena characterconsistsofonlya onepunchedinthe
suppressedtrack,a blankcharacteristransmittedto
System/360.Thecustomerchooseswhichtrackistobe
Ml |i| I
SI
Figure4. 2671 PaperTapeReader:Console [01771]
2671ControlsandLamps5

suppressedandadditionallogiciswiredinbyanIBMcusto-
merengineer.
Whilereading8-tracktapewhenthetrack-suppressswitch
ison,itispossibletoreadtheshiftedbinary-codeddecimal
(BCD)codewhilestillmaintainingoddparitychecking,and
toconsiderseven-holepunchedcharacters(track1to7)as
deletecharacters.Iftrack8 ispunched,thenitisnecessary
towirethistrackforsuppression.
ParitySwitch
Thesettingofthethree-positionparityswitchpermitsa
choiceofparitycheckingwithinthe2671/2822.When set
toNONE,noparitycheckingtakesplace.Whensetto
EVEN,even-paritycheckingcircuitryisactiveforalltracks
ofthetapebeingused.WhensettoODD,odd-paritycheck-
ingcircuitryisactiveforalltracksofthetapebeingused.
Regardlessofthesettingoftheswitch,alltracksaretrans-
mittedtotheSystem/360withoddparity.Whenthewidth
ofthetapeissuchthata trackdoesnotexist,a 0-bitis
transmittedforthattrackposition.
Deletecharactersarenotparitycheckedwhenthedelete
switchison.
2671CONSOLEPUSHBUTTONS
Power-On-and-ResetPushbutton
Iftheremote/localswitch(locatedontheCEpanel)isset
toLOCAL,pressingthepower-on-and-resetpushbutton
suppliesacanddcpowertothe2671.
Forunitsfittedwiththeisolationfeature,thepushbutton
isactiveonlywhenthedegateswitch(locatedinsidethe
unit)issettoON.Withtheremote/localswitchsetto
REMOTE,thepushbuttonisinoperativeandpoweris
suppliedunderthecontrolofSystem/360,butthepush-
buttonstillretainsitsresetfunction.Thechangefromlocal
toremotepowering,andviceversa,canonlybemadeby
theIBMcustomerengineer.
Forunitsnotfittedwiththeisolationfeature,the
power-on-and-resetpushbuttonmustnotbeusedwhenthe
2671 isinlocalmodetoavoidchanneldisturbances(unless
theSystem/360isina waitcondition).
Pressingthepushbutton(evenwhenthepowerison)
resetsthe2671,providedthatnocommandisinprogress.
Power-Off-if-in-Local Pushbutton
Iftheremote/localswitchissettoLOCAL,pressingthe
power-off-if-in-local pushbuttonremovesacanddcpower
fromthe2671.Forunitsfittedwiththeisolationfeature,
thepushbuttonisactiveonlywhenthedegateswitchisset
toON.Whentheremote/localswitchissettoREMOTE,
thepower-off-if-in-localpushbuttondoesnothing,and
powercanonlyberemovedundercontrolofSystem/360.
Thechangefromlocaltoremotepowering,andviceversa,
canonlybemadebytheIBMcustomerengineer.
Providedthatthe2671isinlocalmodeandtheisolation
featureisfitted,thepushbuttonmaybeusedinpowering
procedures,asdescribedona labelattachedtotheunit.
Itisadvisabletoturnthepoweroffwhenthefollowing
conditionsaresatisfied:
1. Unitnotlastonthechannel.
2. Remote/localswitchsettoLOCAL.
3. Noimmediateuseof 2671 expected.
StartPushbutton
Providedallotherreadyconditionsaresatisfied,pressing
thestartpushbuttonputsthe2671ina readycondition,
turnsonthereadylamp,andsignalstheSystem/360thata
papertapereadoperationcanbeinitiated.
StopPushbutton
Ina nonprocessrunout(NPRO)operation,pressingthe
stoppushbuttonstopsthetapeimmediatelyandturnsoff
theNPROlamp.
Ifthe2671isready,butnotreading,pressingthestop
pushbuttonturnsoffthereadylampimmediately.
Ina readoperation,thereadylampturnsoffonlyafter
thereadoperationiscompleted,regardlessofthestatusof
the2671atthecompletionofthereadoperation.
End-of-File Pushbutton
Whenseveralrollsorstripsoftapebelongingtothesame
filehavetoberead,the end-of-file pushbuttonmustbe
keptintheOFFpositionuntilthelastrollorstripoftape
isinsertedinthe2671.Thenthepushbuttonispressedand
theend-of-filelampturnson;the2822isconditionedto
signaltothechannelthatthelasttapeofa filehasbeen
read.
The2671remainsinthereadystateuntilthechannel
issuesa newcommand,whenthestatusunitexceptionis
sentandthe2671becomesnotready.
NPRO(NonprocessRunout)Pushbutton
TheNPROpushbutton,whenoperated,feedstapewithout
processing,ifthefollowingconditionsaresatisfied:
1. Poweron.
2. Readylampoff(ifon,pressstoppushbutton).
3. Tapeproperlyloaded(loadlampoff).
4. ChanneloperatingorunitintheCEmode(off-line).
Thetapecontinuestomoveforwarduntilthestoppush-
button,loadswitch,orpower-on-and-resetpushbuttonis
operated,oranend-of-tapeconditionisdetected,ora
checkconditionoccurs(tapejaminthe2671orinoneof
thestackers,oroverstep).TheNPROpushbuttonisusedto
rewinda rolloftapeafterithasbeenprocessed,provided
thattherolloftapewaspreviouslymovedfromthetake-up
featuretothesupplyfeature.

Step-by-StepPushbutton
Eachtimethestep-by-steppushbuttonispressed,thetape
advancesonecharacterpositionprovidedthefollowingcon-
ditionsaresatisfied:
1. Powerison.
2. Readylampisoff(ifon,pressstoppushbutton).
3. Tapeproperlyloaded(loadlampoff).
4. Unitundersystemcontrol(channeloperating)orinCE
mode.
Thestep-by-steppushbuttonisusedprimarilytoposition
thefirstcharacterof a predeterminedrecordinfrontofthe
readhead.
2671CONSOLELAMPS
Power-On-and-Reset Lamp
Thislamp,whichisincorporatedinthepower-on-and-reset
pushbutton,indicatesthatacanddcpoweraresuppliedto
the2671.
ReadyLamp
Ifthe2671ison-line,thereadylampindicatesthatthe
2671isreadingtape or waitingforinstructionsfromthe
System/360.Thelampturnsonwhenthefollowingcondi-
tionsaresatisfied:
1. Powerison.
2. Tapeisproperlyloaded.
3. Oversteplampisoff.
4. Startpushbuttonispressed.
Thelampturnsoffwhenoneofthefollowingconditions
occurs:
1. Theoperatorhaspressedthestoppushbuttonandthe
readoperationhasbeencompleted.
2. Theoperatorhasretractedthetapeguidesbypressing
theloadswitch.
3. Theoperatorhaspressedthepower-on-and-resetpush-
buttonwhilenocommandisbeingexecuted.
4. Notapeisunderthereadheadandthe end-of-file lamp
isoff.
5. Anoverstephasoccurredontapestop.Sucha situation
mayoccurona tapestopthatisdueeithertoanend-
of-readoperationortochannelcontentionwhena read
operationisinprocess.
End-of-File Lamp
Theend-of-filelampindicatesthattheend-of-filepush-
buttonhasbeenpressed.Thelampturnsoffwhenthe
System/360isinformedthatthelasttapeofthefilehas
beenread(unit-exceptionstatusbyte,orwhenthestop
pushbuttonispressed.
EquipmentCheckLamp
Theequipmentchecklampindicatesthata timeoutcon-
ditionhasoccurred.Eachtimea characterisread,a time
intervalisinitiated.Ifthefollowingcharacterpunchedin
thetapeisnotreadbeforetheendofthetimeallowed
(approximately0.8seconds),a timeoutconditionoccurs,
andtheequipmentchecklampturnson.The2671stops,
andthereadylampstayson.Anyofthefollowingcon-
ditionscancausea timeoutcondition:
1. The tape jammed. Freethetapeandsplicethedamaged
portions.Positionthetapeeitheratthebeginningofthe
record,atthebeginningofthetape,oratthebeginning
ofthenextrecordandreadthetapeagain.(Theactual
proceduredependsontherequirementsoftheparticular
jobintheprogram.)
2. A length of tape was not punched. Atthemaximum
speedofthe2671,about5 ft(1,52m)ofunpunched
tapecanbereadbeforeanequipmentcheckoccurs.The
programnormallyignoresanequipment checkofthis
kindandthe2671continuestoreadwithoutoperator
intervention.
3. An unusual intervention.
4. Failure of the photocell reading system.
5. Failure of the tape drive motor.
Theequipmentchecklampisturnedoffwhena new
operationisinitiated,orwhensystemresetisperformed.
DataCheckLamp
Thedatachecklampindicatesthata parityerrorhasbeen
detected.Theerroneouscharacteristransmittedtothe
System/360.The2671stops,andthereadylampremains
on.Theerroneouscharacterremainsinthedataregister.
Thedatachecklampisturned off whena newread
operationisinitiated,orwhensystemresetisperformed.
NPROLamp
TheNPROlampindicatesthattheNPROpushbuttonhas
beenpressed.Thelampturnsoffwhenthestopor
power-on-and-resetpushbuttonorreloadswitchispressed,
anend-of-tapeisdetected,oranoverstepora checkcon-
ditionoccurs.
OverstepLamp
Theoversteplampindicatesthata characterhasbeenlost
ona tapestop.Thisconditionturnsoffthereadylamp.
Thepower-on-and-resetpushbuttonturnsofftheoverstep
lamp. Becauseofinertiainthelampcontrolfeedback
system,switchingonandoffmayoccasionallyturnonthe
oversteplamp.Insuchcases,usethepower-on-and-reset
pushbuttontocleartheerror.
LoadLamp
Theloadlampindicatesthatthetapeguidesareretracted.
(Theright-handtopkeyisstilldepressed.)
Off-LineLamp
Theoff-linelampindicatesthatthe2671isintheCE
mode.
2671 ControlsandLamps7

HOURSCOUNTER
Elapsedtimeinhoursandminutesisindicatedonthe
counterlocatedonthe 2671 console.Thecounteroperates:
1. Fromthefirstreadcommanduntil a run-outcondition
(endoftape)hasbeendetected.
2. Duringa taperewindoperation,providedthe2671is
notoff-lineandtheSystem/360isnotintheCEtest
mode.
2671READERPLATESWITCHES
Theswitcheslocatedonthereaderplate(Figure5)areof
themechanicaltype.
LoadSwitch
Theloadswitchisa two-positionswitchconsistingofright-
handandleft-handtopkeys.
Pressingtheright-handtopkey(loadkey)turnsonthe
loadswitchandretractsthetapeguidesfortapeloadingor
unloading.Pressingtheleft-handtopkeyturnsofftheload
switchandpositionsthetapeguidesfortapereading.When
on,theloadswitch:
1. Resetsthebuffer.
2. Clearsthedataregister.
3. Stopsthetapeimmediatelywhenitisrunning(NPRO
lamporreadylampgoesout).
4. Turnsofftheoversteplamp.
SupplySwitch
Thesupplyswitchisusedonlywiththesupplyfeature.
Thisswitchissetwhenthesupplyclutchleverisperpen-
diculartothesupplystackerandissetoffwhenthesupply
clutchleverisinlinewiththesupplystacker.
Whenon,theswitchallowsthesupplyclutchtofeedthe
tapefromthereelunderthecontrolofthesupplystacker
photocells.Whenoff,theswitchpreventsthesupplyclutch
fromengaging.
CAUTION
Whenthesupplyfeatureisused,itiscompulsorytoset
thesupplyclutchleverperpendiculartothesupply
stacker.Forgettingthisstepwillresultinthetapebeing
pulleddirectlybythereaderclutchandthetapemay
sufferdamage.
RotatingTab
Therotatingtabisonlysuppliedwiththetake-upfeature.
Therotatingtaboperatesa microswitch(calledthetake-up
switch),housedinthetake-upstackerguide.Whenthetab
ispressedagainstthestackerguide,thetake-upmotoris
turnedoffbythetake-upswitch,andthetabdeflectsthe
tapeforward(seeFigure 17).
Whentherotatingtabisinlinewiththetake-upstacker,
thetake-upmotorisfreetooperateunderthecontrolof
thetake-upstackerphotocells.
TurntableKey
RotatingTab Left-HandRight-Hand
TopKeyTopKey Tape-Width Selector
Figure5.2671PaperTapeReader:ReaderPlate[08311]

Tape-WidthSelector
Thethreepositionsofthetape-widthselectorcorrespond
tothethreepositionsofthetape-widthlever,whichcan
adjustthetapeguidestothethreedifferentwidthsoftape
toberead.
Thesettingoftheselectorisinternallydetectedtocon-
trolthetransferofdatatothebuffer,asfollows:
Tape-Width
Lever Setting Tape Width Transferred Tracks
8 1 inch 1 to8
6,7 7/8 inch 1 to 6,7
511/16inch 1 to5
TurntableKey
Theturntablekeyisspringloaded.
Pullingthekeyforwardunlocksthe two-sided rotatable
supplyturntabletoallowselectionofthesupplyfeatureor
thecenter-rollfeature.Thekeyautomaticallyspringsback
intopositiontolocktheturntableattheselectedfeature.
2671 ControlsandLamps9

OperationalCharacteristics
INTERFACE
The2671isconnectedtotheSystem/360 I/O multiplexer
orselectorchannelthroughthe2822.The 2822-to-channel
connectioniscalledthe I/O interface.Theinterfaceconsists
ofa setofwiresoverwhichthedataandcontrolsignalsare
sent.A summaryofthelinesintheinterfaceisasfollows:
Initial Selection Sequence Response Times
(microseconds)
'Operationalin'upresponseto'selectout'up1.9to4.2
'Addressin'upresponseto'addressout'down1.4to3.3
'Addressin'downresponseto'commandout'up4.4to8.8
'Statusin'upresponseto'commandout'down3.0to6.6
'Statusin'downresponseto'serviceout'up2.4to5.2
Buses (18 Lines)
BusOut(9)
BusIn(9)
Tags (6 Lines)
AddressOut
CommandOut
ServiceOut
AddressIn
StatusIn
ServiceIn
Selection Controls (7 Lines)
SelectOut
SelectIn
HoldOut
RequestIn
OperationalOut
OperationalIn
SuppressOut
Metering Controls (3 Lines)
MeteringOut
MeteringIn
ClockOut
Channel-> I/O Unit(s)
Channel «- I/O Unit(s)
Channel->• I/O Unit(s)
Channel•**• I/O Unit(s)
Channel-H/O Unit(s)
Channel-*-I/O Unit(s)
Channel <- I/O Unit(s)
Channel^I/O Unit(s)
Channel-*I/O Unit(s)
Channel-*-I/O Unit(s)
Channel ->• I/O Unit(s)
Channel-*-I/O Unit(s)
Channel-*-I/OUnit(s)
Channel +- I/O Unit(s)
Channel -> I/O Unit(s)
Channel-> I/O Unit(s)
Channel^I/O Unit(s)
Channel^I/O Unit(s)
Theselect-outlineisbypassedwhenthepower-off-if-in-
local pushbuttononthe2671ispressed.Whenthepower-
on-and-resetpushbuttonispressed,thelogicofthe
2671/2822isreset,andtheselect-outbypassisreleased.
Whenoperatingatfullspeed(1,000characterspersecond
+25percentvariation),the'requestin'lineisactivated
every0.8milliseconds.Sothat2671mayoperatecontin-
uously,a datacharactermustbeacceptedbythechannel
within0.8millisecondsafterthe'requestin'lineis
activated.
InterfaceTiming
Thefollowingchartspecifiesminimumandmaximum
responsetimesforallinterfacesignalsequences.Thefunc-
tionsofthesesignalsarethosedefinedbythestandard
interfaceforSystem/360.
Data Transfer Sequence
'Operationalin'upresponseto'selectout'up
'Addressin'upresponseto'selectout'up
'Addressin'downresponseto'commandout'up
'Servicein'upresponseto'commandout'down
'Servicein'downresponseto'serviceout'up
Response Times
(microseconds)
1.7to3.8
3.1 to 6.8
0.6to2.5
3.3 to 7.1
2.7 to 5.5
ADDRESSING
The2671isaddressedbysendingeightbitsofaddressplus
aparitybitovertheninebus-outlines.The2671is
equippedwithanaddresscardwhichisadjustedtoagree
withtheaddresssetupbytheprogram.Thiscardcanbe
adjustedonlybyanIBMcustomerengineer.Anyoneof
256bitcombinationsisvalidasanaddressforthe 2671.
COMMANDS
The2671canacceptalltheSystem/360 I/O commands
withtheexceptionofreadbackwardandwrite,whichare
treatedasinvalidcommands.Thevalidcommandsforthe
2671are:
BitPositions
Read
ReadModified
Sense
Test I/O
Control
P
0
1
0
1
1
0
0
0
0
0
0
1
0
0
0
0
0
2
0
0
0
0
0
3
0
0
0
0
0
4
0
0
0
0
0
5
0
1
1
0
0
6
1
1
0
0
1
7
0
0
0
0
1
Onlythereadandreadmodifiedcommandswillinitiatea
readoperationinthe2671/2822.
Withthe'read'command(bit5 = 0),thereadoperation
endsonlyifthecountinthechannelcontrolwordreaches
zero.
OperationalCharacteristics 11

With'readmodified'commands(bit5 = 1),theread
operationcanbeendedif:
1. EORcharacterdetected.
2. Countinthechannelcontrolwordreacheszero.
Thesensecommandgatesbackthesensebytesofthe
2671/2822totheSystem/360.
Thetest I/O instructionisgivenbytheSystem/360pro-
gramtochecktheavailabilityofthe2671/2822,ifithas
notbeenaccessedforsometime.
STATUSBYTES
ThestatusbyteinformstheSystem/360ofthecurrent
statusofthe2671/2822:
Bit Condition
0
1
2
3
4
5
6
7
Notused
Notused
Notused
Busy
ChannelEnd
DeviceEnd
UnitCheck
UnitException
Allbitsofthestatusbyteareresetwhenthebyteis
acceptedbySystem/360,withtheexceptionofbits3 and6
ifthe2671/2822isnotready(readylampoff).Bit6 isset
onifanyofbits0 through2 ofthesensebyteareon.
ExamplesofStatusBytes
Busy
Abusystatusbyteisreturned toa newcommandwhenthe
2671isstillexecutingthepreviouscommandandbefore
anyendstatus(includingchannelend)isgeneratedinthe
2822.
Channel End
Achannelendstatusbyteindicatesthattransmissionof
datacharactersovertheinterfacefora givencommandhas
beencompleted.
Device End
Thedeviceendindicatesthatthe2671hasbeenrestored
fromanyoneofthenot-readyconditionstoa readycon-
dition.
Unit Check
Theunit-checkstatusbyteissenttothesystemtorejecta
command.A sensecommandcanbeissuedbythesystem
tointerrogatethe2671astowhythecommandwasrejec-
ted.Notethata sensecommandisacceptedwitha blank
statusevenwhentheunitgeneratesunitcheckbecauseofa
not-readysituation.
Sense Bit 0 (Command Reject): Invalidcommand.
Sense Bit 1 (Intervention Required): The2671/2822isunableto
performa readoperation.
Sense Bit 2 (Bus-Out Check): Incorrectparityofa validorinvalid
command.
Unit Exception
Theunit-exceptionstatusbyteisissuedbythe2671to
rejectthefirstcommandfollowingtheendofthelasttape
ofa file (end-of-file lampon).Thestatusofthe2671
becomesnot-readyafterissuingthisstatusbyte.
Busyand Device End
Ifthedevice-endinterrupt,generatedbythe
not-ready-to-readytransition,isstacked,anysubsequent
validcommand(excepttest I/O) isrejected.Busyand
device-endisreturnedtothechannel.
Busy and ChannelEnd and Device End
Thebusyandchannel-endanddevice-endstatusbyte
rejectsanycommand,excepttest I/O, whensucha com-
mandisissuedafterchannel-endanddevice-endwas
generatedinthe2822andbeforethestatusbyteisaccep-
tedbythechannel.
Busyand Channel End and Device End and Unit Check
Thebusyandchannel-endanddevice-endandunit-check
statusbyterejectsanycommand,excepttest I/O, when
sucha commandisissuedafterchannel-endanddevice-end
andunit-checkwasgeneratedinthe2822andbeforethe
statusbyteisacceptedbythechannel.
Channel End and Device End
Thechannel-endanddevice-endstatusbyteistransmitted
totheSystem/360eachtimea tapereadoperationhasbeen
properlyperformed.Ifthemodifierbitisnotpresentinthe
readcommandbyte,thereadoperationiscompletedupon
receivinga stopsignalfromthesystem(charactercount
equalszero).Ifthereadcommandbytecontainsthemodi-
fierbit,thereadoperationisnormallystoppedwhenan
EORcharacterisdetectedbythe2671.(TheEORcharac-
terisnottransmittedtothesystem.)Thechannel-endand
device-endstatusbytecanalsobegeneratedbyan end-of-
tapeatthereadhead.
Channel-endanddevice-endisreturned:
1. To a halt I/O whenhalt I/O occursafterinitialselection
andbeforechannel-endispresented.
2. To a control no-operation (NOP) whennostatusinfor-
mationispending.
3. To a test I/O issuedaftera channel-endanddevice-end
statuswasgeneratedandbeforeitisacceptedbythe
channel.
Assoonasthechannel-endanddevice-endstatusbyteis
acceptedbythesystem,the2671becomesnot-ready(sense
12

bit 1, interventionrequired,turnson)ifoneofthefollow-
ingconditionsissatisfied:
1. Anend-of-tapeisdetected(EOFpushbuttonnotoper-
ated).
2. Anoverstepoccursona normaltapestop,excepton
channelcontentionandsupplystackerstops.
3. Thestoppushbuttonisoperatedduringthetaperead
operation.
Channel End and Device End and Unit Check
Thechannel-endandthedevice-endandunit-checkstatus
byte, whenissued,indicatesthatanunusualconditionhas
occurredinthe2671topreventfurtherdatacharacters
beingreadproperly.Operatorinterventionmaybe
required,dependentuponthesensebitthatsetunitcheck.
Byissuinga sensecommand,theSystem/360program
determinestheexactconditionthatcausedthechannel-end
anddevice-endandunit-checkstatusbyteissuedbythe
2671, asfollows:
Sense Bit 1 (Intervention Required): Indicatesthatthe2671
becamenot-readybeforethenormalcompletionofa readoperation
(forexample,overstepona tapestopbecauseofthechannelcon-
tention,a supplystackerstop,ortheloadswitchpressed).
Sense Bit 3 (Equipment Check): Indicatesthata timeouthas
occurredsincethelastdatacharacterwasread.A timeoutcondition
iscausedbya 2671(unit)failureorbydetectionofa lengthof
blanktape.The2671remainsina readystatus.TheSystem/360
programcaninitiatea newreadcommandorrequestoperatorinter-
vention.
Sense Bit 4 (DataCheck): Indicatesthatincorrectparityhasbeen
detectedona datacharacter.However,thisdatacharacteristrans-
mittedtothesystem I/O channel,andthe2671remainsina ready
status. TheSystem/360programcaneitherinitiatea newreadcom-
mandorrequestoperatorintervention.
Channel-endanddevice-endandunit-checkisalso
returnedtoa test I/O commandissuedafterthestatusbyte
was generatedandbeforethestatusbyteisacceptedbythe
channel.
SENSEBYTES
Whena sensecommandisreceivedbythe2671,onebyte
ofsenseinformationistransmittedtothesystem I/O chan-
nel. Thefollowingbitassignmentisusedinthesensebyte:
Bit Condition
0
1
2
3
4
5
6
7
CommandReject
InterventionRequired
BusOutCheck
EquipmentCheck
DataCheck
Notused
Notused
Notused
Theseconditionsareresetatthebeginningofthenext
readcommandwiththeexceptionof'intervention
required',whichisresetbypressingthestartpushbutton
afterallrequirementsfora readyconditionaresatisfied.
ExamplesofSenseBytes
Command Reject
Thecommandrejectconditionisdetectedwhena read
backwardora writecommandisreceivedatthe2671,or
whenvalidcommandshaveinvalidmodifierbits.A parity
erroronthecommandpreventsthecommandrejectcon-
ditionfrombeingdetected,andinsteada bus-outcheck
conditionoccurs.
Intervention Required
Theintervention-requiredconditionmeansthatthe2671is
notready.(Thisisbestdescribedbystatingtheconditions
forready.)The2671isreadywhen:
1. Powerison.
2. Tapeisproperlyloaded.
3. Oversteplampisoff.
4. Startpushbuttonispressed.V
The 2671 becomesnot-readyimmediatelywhen:
1. Thestoppushbuttonispressedwhilenoreadoperation
isinprogress.
2. Theloadswitchispressed.
3. Thepower-on-and-resetpushbuttonispressed.
The2671becomesnot-readyattheendofa readoper-
ationwhen:
1. Thereisanoverstepconditionona normalor abnorma
tapestop.Theoverstepconditionisresetbypressingthe
loadswitchorthepower-on-and-resetpushbutton.
2. Theendoftapeisdetectedatthereadhead(EOFlamp
beingoff).
3. Thestoppushbuttonhasbeenoperatedduringtheread
operation,anda normalorabnormalcompletionhas
occurred.
Assoonasthe2671isrestoredfromanyoneofthenot-
readyconditionstothereadycondition,a device-end
interruptisgeneratedtoinformtheprogramofthis
transition.
Bus-Out Check
Bus-outcheckissetwhena parityerrorhasbeendetected
fora commandissuedbytheSystem/360.
Equipment Check
Theequipment-checksensebitindicatesthata timeouthas
occurredinthe 2671 sincethelastdatacharacterwasread.
Thistimeoutcouldbecausedby:
1. A failureofthephotocellsorthelightprojectionsys-
tem.
2. A tapedrivemotorfailure.
3. Anunusualtapecreepingcondition.
4. A lengthofblanktape.
5. Tapejamminginthestackers.
OperationalCharacteristics13

Data Check
Ina datacheck,theparityof th§ data,exceptrecognized
EORcharactersanddeletecharacters,canbecheckedifthe
parityswitchissettotheoddorevenposition.Regardless
ofthetapecodeused,thedatasentfromthe2822tothe
channelhasoddparity.
TAPECODETRANSLATION
The2671iscapableofreadinganytapecodethatcanbe
punchedin5-,6-,7-,or8-tracktape.(Feed holesaloneare
ignored.)Thisispossiblebecausethetranslationofthe
codepunchedinthetapeisdonebySystem/360.Theeight
tracksofthe2671areconnectedtothesystem I/O channel
bybus-inlinesasfollows:
trackNumber8 7 6 5 4 3 2 1 OddParity
lllllllll
Bus-InLine 01234567P
Whenthewidthofthetapeissuchthata trackdoesnot
exist,a 0-bit istransmittedforthattrackposition.
Theeightbus-inlinesconnecttotheeightbitsofa core-
storagebyteintheSystem/360asfollows:
Bus-InLines
CoreStorage
0 12 3 4 5 6 7
0 12 3 4 5 6 7
Aholepunchedina trackofpapertapeisrepresentedas
a1-bitinitsrespectivepositionofcorestorage.A blankin
atrackofpapertapeisrepresentedasa 0-bitinits
respectivepositionofcorestorage.
ThetranslateinstructionintheSystem/360maybeused
toconvertthetapecodetothedesiredinternalcode.The
translateinstructionoperatesbyaddingthebinaryvalue
representedbythetapecodetothestartingaddressofa
table.Thesumofthesetwonumbersistheaddressofa
positioninthetablethatcontainsthedesiredinternal
extendedbinary-coded-decimalinterchangecode(EBCDIC)
orUnitedStatesofAmericastandardcodeforinformation
interchange(USASCII)codeforthecharacter.Theinternal
codeisautomaticallytakenfromthetabletoreplacethe
tapecodeintheread-inarea.
SpecialTapeCodeCharacters
End-of-Record Character
TheEORcharacterischosenbythecustomerfromamong
thesparecodesofthetapecode.Theend-of-record
switchesonthe 2671 consoleallowthecustomertogener-
atethecodingofthechosenEORcharacter.
Thestateoftheend-of-recordswitchesiscontinuously
comparedwitheachcharacterreadbythe2671.
Ifthe2671isoperatingunderthecontrolofmodified
-»read commands,the2671stopsateachEORcharacter.
NoneoftheEORcharactersistransmittedtothechannel.
Ifthe2671isoperatingunderthecontrolofunmodified
readcommands,the2671stopsonlywhenthechannelcon-
trolwordcountreacheszero.EORcharactersuptothis
pointaretransmittedtothechannelandarecountedas
datacharacters.
Theonecondition,however,whereanEORcharacteris
transmittedtoSystem/360undera modifiedreadcom-
mandisasfollows:
System/360 programchangesfromanunmodifiedread
commandtoa modifiedreadcommand,andthefirst
characterofthenewrecordisanEORcharacter.
TheEORcharacterisnotparitychecked.
IftheEORcharacterisusedtoindicatetheendsofa
seriesoffixed-lengthrecords,itisadvisabletoissuesucces-
sivemodifiedreadcommands,ratherthanunmodifiedread
commandsthatarefollowedbyonemodifiedreadcom-
mand.Thisenablesthetranslationprogramtotakeplaceat
theendofeachrecord,ratherthanattheendofthe com-
plete tape.
Delete Character
Thedeletecharacteristhatcharacterhavingallpossible
trackspunched.Thedeletecharacterhasthisformatforall
5-, 6-,7-,and8-trackcodes.
Ifa mistakeinthepunchingofa characterismade,the
badcharacteriserasedbypunchingallremainingtracks.
Thedeletecharacterisautomaticallysuppressedinthe
2671providedthatthedeleteswitchhasbeenpushedup.
The2671doesnotstop,andthecharactercountinthe
channelisunaffected.Thedeletecharacterisnotparity
checked.
NORMALSTOPCONDITIONS
CharacterCountEqualsZeroorEORCharacter
Aftera 2671operationhasbeencompleted,thestopsignal
comeseitherfromthesystem(whenthecharactercount
equalszero)orfromthedetectionofanEORcharacter.
Thereadylampremainson.Nooperatorinterventionis
requiredexceptwhenthestoppushbuttonwaspreviously
operated.Ifthestoppushbuttonwasoperatedduringthe
readoperation,thereadylampturnsoff,andthestart
pushbuttonmustbeoperatedtoresumethereadoperation.
CharacterCountEqualsZero
Whenthe2671isstoppedbytheSystem/360becausethe
charactercountequalszero,thethirdcharacterofthenext
recordislocatedatthereadinghead,thesecondcharacter
inthebuffer,andthefirstcharacterinthedataregister.
Thefirstcharacterisreadytobetransferredwhena new
readoperationisinitiatedbytheSystem/360.
14