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SM3E Datenblatt(PDF) 7 Page - Connor-Winfield Corporation |
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SM3E Datenblatt(HTML) 7 Page - Connor-Winfield Corporation |
7 / 36 page SM3E Data Sheet #: TM054 Page 7 of 36 Rev: 04 Date: 01/26/11 © Copyright 2011 The Connor-Winfield Corp. All Rights Reserved Specifications subject to change without notice Detailed Description continued TheM/SOutputortheOutput1ofeachdevicemaybecross-connectedtotheotherdevice’sM/SRefinput.Thedeviceauto- detectsthefrequencyontheM/SRefinput.MasterorslavestateofadeviceisdeterminedbytheM/Spin.Thus,master/slavestateis alwaysmanuallycontrolledbytheapplication.Themastersynchronizestotheselectedinputreference,whiletheslavesynchronizes totheM/SRefinput.(Notethat8kHzframephasealignmentismaintainedacrossamaster/slavepairofdevicesonlyifM/SOutputis usedasthecrosscouplesignal.) Theunitoperatinginslavemodelocksonandphase-alignstothecross-referenceclock(M/SOutputorOutput1)fromtheunit inmastermode.Thephaseskewbetweentheinputcross-referenceandtheoutputclockfortheslaveunitistypicallylessthan±1ns (under±3nsindynamicsituations,includingreferencejitterandwander). PerfectphasealignmentofthetwoOutput1outputclockswouldrequirenodelayonthecross-referenceclockconnection.To accommodatepathlengthdelays,theSM3Eprovidesaprogrammablephaseskewfeature.Theslave’sOutput1orM/SOutputmay bephaseshifted-32nSto+31.75nSrelativetoM/SInputaccordingtothecontentsoftheMS_Phase_Offsetregistertocompensate forthepathlengthoftheM/SOutputorOutput1toM/SInputconnection.Thisoffsetmaythereforebeprogrammedtoexactly compensatefortheactualpathlengthdelayassociatedwiththeparticularapplication’scross-referencetraces.Theoffsetmayfurther beadjustedtoaccommodateanyoutputclockdistributionpathdelaydifferences.Thus,master/slaveswitcheswiththeSM3devices maybeaccomplishedwithnear-zerophasehits. Thefirsttimeaunitbecomesaslave,suchasimmediatelyafterpower-up,itsoutputclockphasestartsoutarbitrary,andwill quicklyphase-aligntothecross-referencefromthemasterunit.Thephaseskewwillbeeliminated(orconvergedtotheprogrammed phaseoffset)stepbystep.Thewholepull-in-and-lockprocesswillcompleteinabout60seconds.Thereisnofrequencyslew protectioninslavemode.Inslavemode,theunit’smissionistolocktoandfollowthemaster. Onceapairofunitshasbeenoperatinginalignedmaster/slavemode,andamaster/slaveswitchoccurs,theunitthatbecomes masterwillmaintainitsoutputclockphaseandfrequencywhileaphasebuild-out(tothecurrentoutputclockphase)isperformedon itsselectedreferenceinput.Therefore,asmastermodeoperationcommences,therewillbenophaseorfrequencyhitsontheclock output. Likewise,theunitthatbecomestheslavewillmaintainitsoutputclockfrequencyandphasefor1msecbeforestartingtofollowthe cross-reference,protectingthedownstreamclockusersduringtheswitch.Assumingthephaseoffsetisprogrammedfortheactual propagationdelayofthiscross-referencepath,therewillagainbenophasehitsontheoutputclockoftheunitthathastransitioned frommastertoslave. Master / Slave Configuration Figure 3 STC3500 SM3E M/S_OUT / OUTPUT1 / BITS M/S_OUT / OUTPUT1 / BITS M/S REF REFS1-8 REFS1-8 M/S REF 2 SM3E 1 Furthermore,underregisteraccesscontrol,abackupholdoverhistoryregisterisprovided.Itmaybeloadedfromtheactive holdoverhistoryorrestoredtotheactiveholdoverhistory.Theactiveholdoverhistorymayalsobeflushed. Holdovermodemaybeenteredatanytime.Ifthereisnoholdoverhistoryavailable,theprioroutputfrequencywillbemaintained. Wheninholdover,theapplicationmayread(viaregisteraccess)thetimesinceholdoverwasenterred. Master/Slave Operation PairsofSM3Edevicesmaybeoperatedinamaster/slaveconfigurationforredundanttimingsourceapplications.Atypical configurationisshownbelow.: |
Ähnliche Teilenummer - SM3E_15 |
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Ähnliche Beschreibung - SM3E_15 |
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