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AUDIOSERIALINTERFACE
AUDIODATAFORMATSANDTIMING
PCM1609A
SLES145–AUGUST2005
theaudioserialinterfaceforthepcm1609aconsistsofa5-wiresynchronousserialport.itincludeslrck
(pin41),bck(pin40),data1(pin45),data2(pin46),data3(pin47),anddata4(pin31).bckistheserial
audiobitclock,andisusedtoclocktheserialdatapresentondata1,data2,data3,anddata4intothe
audiointerfaceserialshiftregister.serialdataisclockedintothepcm1609aontherisingedgeofbck.lrckis
theserialaudioleft/rightwordclock.itisusedtolatchserialdataintotheserialaudiointerfaceinternalregisters.
bothlrckandbckmustbesynchronoustothesystemclock.ideally,itisrecommendedthatlrckandbck
bederivedfromthesystemclockinput,scki.lrckisoperatedatthesamplingfrequency(f
S
).bckcanbe
operatedat32,48,or64timesthesamplingfrequency(i
2
SformatdoesnotsupportBCK=32f
S
).
internaloperationofthepcm1609aissynchronizedwithlrck.accordingly,internaloperationofthedeviceis
suspendedwhenthesamplingrateclock(lrck)ischanged,orwhensckiand/orbckisinterruptedatleastfor
a3-bitclockcycle.ifscki,bck,andlrckareprovidedcontinuouslyafterthissuspendedstate,theinternal
operationisresynchronizedautomaticallywithinaperiodoflessthan3/f
S
.duringthisresynchronizationperiod
andfora3/f
S
timethereafter,theanalogoutputsareforcedtothebipolarzerolevel,v
CC
/2.externalresettingis
notrequired.
thepcm1609asupportsindustry-standardaudiodataformats,includingstandard,i
2
s,andleft-justified(看
Figure22).dataformatsareselectedusingtheformatbits,fmt[2:0],inregister9.thedefaultdataformatis
24-bitstandard.allformatsrequirebinary2scomplement,msb-firstaudiodata.看Figure23foradetailed
timingdiagramoftheserialaudiointerface.
data1,data2,data3,anddata4eachcarrytwoaudiochannels,designatedastheleftandrightchannels.
theleft-channeldataalwaysprecedestheright-channeldataintheserialdatastreamforalldataformats.
Table2showsthemappingofthedigitalinputdatatotheanalogoutputpins.
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