參數(shù)資料
型號： SM3E-19.44M
廠商： Connor-Winfield
文件頁數(shù)： 21/36頁
文件大?。?/td> 0K
描述： IC MOD TIMING 19.440MHZ STRAT 3E
標(biāo)準(zhǔn)包裝： 1
系列： SM3
類型： 定時模塊，系統(tǒng)時鐘
PLL： 是
主要目的： 以太網(wǎng)，ADM，DSLAM，SONET/SDH，Stratum，TDM
輸入： LVCMOS
輸出： LVCMOS
電路數(shù)： 1
比率 - 輸入:輸出： 8:3
差分 - 輸入:輸出： 無/無
頻率 - 最大： 19.44MHz
電源電壓： 3.135 V ~ 3.465 V
工作溫度： 0°C ~ 70°C
安裝類型： 通孔
封裝/外殼： 32-DIP 模塊
包裝： 管件
其它名稱： CW643
SM3E 19.44M
SM3E19.44M
SM3E Data Sheet #:
TM054
Page 28 of 36 Rev: 04 Date: 01/26/11
Copyright 2011 The Connor-Winfield Corp. All Rights Reserved
Specifications subject to change without notice
Application Notes continued
Boundary Scan IEEE1149.1-2001 (Limited Testability Support) - Thismoduleexposesaboundaryscanchainwhichcontains
oneormoreboundaryscantestableIEEE1149.1-2001complaintdevices.TheexposedboundaryscanchainisIEEE1149.1-2001
compliant,andsupportsalldocumentedtestingmodesofdevicescontainedwithinchain.Integrationofthismoduleintoanexisting
boundaryscanchainwillrequirethefollowing.
-Substitutionofmodulesfootprintwithprovidedtestabilitymodelschematic.
-Modifiednetlistwillneedtobeloadedintoboundaryscantestvectorgenerationsoftware.
TestabilityModelSchematicandBSDLfile(s)canbeobtaineddirectlyfromfactory.
Control Modes
Thedevicemustbeoperatedinamanualcontrolmode,orautomaticcontrolandreferenceselectionmode.
Reset maybepulledlowforaminimumof10mSduringchipstart-up(oranyotherdesiredtime)toinitializethefulldevicestate.
TheBITSclockoutputfrequencyisselectedbythe
T1/E1pin.WhenT1/E1=1,theBITSfrequencyis1.544MHz,andwhen
T1/E1=0,theBITSfrequencyis2.048MHz.
MASTER SELECT-Determinesthemasterorslavemode.Setto“1”foramaster,and“0”foraslave.Master/slaveswitches
shouldbeperformedwithminimaldelaybetweenswitchingthestatesofeachofthetwodevices.Thiscanbeeasilyaccomplished,for
example,bycontrollingthemaster/slavestatewithasinglesignal,coupledtooneofthedevicesthroughaninverter.
Forsimplexoperation,thedeviceshouldbeinMastermode-set
MASTER SELECTto“1”.
Holdover History Accumulation and Maintenance continued –Wheneverholdoverisentered,itistheActiveHoldoverHistory
thatisusedtodeterminetheholdoverfrequency.TheHistory_Cmdregisterallowstheapplicationtoissuethreeholdoverhistory
controlcommands:
1)SavetheActiveHoldoverHistorytotheBackupHistory.
2)RestoreaBackupHistorytotheActive.
3)FlushtheactiveHistoryaswellastheaccumulationregister.TheBackuphistoryremainsintact.
BoththeActiveandtheBackupholdoverhistoriesareloadedwiththecalibratedfreerunsynthesizercontroldataonreset/power-up.
Theapplicationmightusethe“savetobackup”inasituationwhere,forexample,theprimaryreferenceisknowntobeofhigher
qualitythananysecondaryreferences,inwhichcaseitmaybedesirabletosaveandthenrestoretheholdoverhistoryaccumulated
ontheprimaryreferenceiftheprimaryreferenceislostandholdoverisentereduponlossofasecondaryreference.Userscanrestore
thehistoryfrombackupanytime,evenwhileoperatinginHoldovermode.Thefrequencytransientwillbesmoothandcontinuous.
Itistheresponsibilityofapplicationsoftwaretokeeptrackoftheageandviabilityoftheholdoverbackuphistory.Giventimeand
temperatureeffectsonoscillatoraging,theapplicationmaywishtoperiodicallyperforma“Save”oftheActivehistorytokeepthe
backupcurrent.
Whenswitchingtoanewreference,theactiveholdoverhistorywillremainintactandmarkedas“HoldoverAvailable”(ifitwas
availablebeforethereferenceswitch)untilanewhistoryisaccumulatedonthenewreference(Typically15minutesafterlockhas
beenachieved).Duringthenewhistoryaccumulation,the“HoldoverBuildComplete”bitisreset.Oncethenewhistoryaccumulationis
complete,itistransferredtotheActiveHistoryandthe“HoldoverBuildComplete”bitisset.Theactivehistorywillthencontinuetobe
updatedtotrackthereference.
TheHistory_Policyregisterallowstheapplicationtocontrolhowanewhistoryisbuilt.Whensetto“Rebuild”:
1)Historyaccumulationbeginswhenlockisachievedonthenewreference.
2)Theholdoverhistoryisrebuilt(takingabout15minutes).TheActiveHistoryremainsuntoucheduntilitisreplacedwhenthebuild
iscomplete.
Whenthepolicyissetto“Continue”:
1)Ifthereisno“Available”ActiveHistory,anewbuildoccurs,asunderthe“Rebuild”policy.
2)Ifthereisan“Available”ActiveHistory,itwillcontinue,theaccumulationregisterwillbeloadedfromthe
ActiveHistory,andthe“Build”processisessentiallycompletedimmediatelyfollowinglockonthenewreference.
The“Continue”policymaybeusedbytheapplicationif,forexample,itisknownthatthereferenceswitchedtomaybetracedtothe
samesourceandthereforelikelyhasnofrequencyoffsetfromthepriorreference.Inthatcase,the“Continue”policyavoidsthedelay
ofrebuildingtheholdoverhistory.Iftheswitchislikelytobebetweenreferenceswithknownorunknownfrequencyoffset,thenitis
preferabletousethe“Rebuild”policy.
ThetimesincetheholdoverstatewasenteredmaybereadfromtheHoldover_Timeregister.Valuesarefrom0to255hours,
limitedat255,andresetto0whennotintheholdoverstate.
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