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电源-在-resetfunctions
重置 重置 释放
V
CC
3.7 v
3 v
2.2 v
内部的 重置
系统 时钟
t0014-06
0 v
don’t 小心 3072 系统 clocks
AudioSerialInterface
AudioDataFormatsandTiming
pcm1780,pcm1781,pcm1782
SLES132A–MARCH2005–REVISEDAPRIL2005
thepcm1780/81/82includesapower-在-resetfunction.figure21showstheoperationofthisfunction.withthe
systemclockactiveandV
CC
>3v(典型,2.2vto3.7v),thepower-在-resetfunctionisenabled.这
initializationsequencerequires3072systemclocksfromthetimeV
CC
>3v(典型,2.2vto3.7v).afterthe
initializationperiod,thepcm1780/82issettoitsresetdefaultstate,asdescribedinthe
ModeControlRegister
sectionofthisdatasheet.
duringtheresetperiod(3072systemclocks),theanalogoutputisforcedtothecommonvoltage(v
COM
),或者
V
CC
/2.aftertheresetperiod,theinternalregisterisinitializedinthenext1/f
S
periodandifsck,bck,andlrck
areprovidedcontinuously,thepcm1780/81/82providestheproperanalogoutputwithagroupdelay
correspondingtotheinputdata.
figure21.电源-在-resettiming
theaudioserialinterfaceforthepcm1780/81/82consistsofathree-wiresynchronousserialport.itincludes
lrck(pin8),bck(pin7),anddata(pin6).bckistheserialaudiobitclock,anditisusedtoclocktheserial
datapresentondataintotheserialshiftregisteroftheaudiointerface.serialdataisclockedintothe
pcm1780/81/82ontherisingedgeofbck.lrckistheserialaudioleft/rightwordclock.itisusedtolatchserial
dataintotheinternalregistersoftheserialaudiointerface.
bothlrckandbckshouldbesynchronouswiththesystemclock.ideally,itisrecommendedthatlrckand
bckbederivedfromthesystemclockinput,sck.lrckisoperatedatthesamplingfrequency,f
S
.bckcanbe
operatedat32,48,or64timesthesamplingfrequency.
internaloperationofthepcm1780/81/82issynchronizedwithlrck.accordingly,internaloperationofthe
deviceissuspendedwhenthesamplingrateclock,lrck,ischangedorsckand/orbckisinterruptedatleast
forthreebit-clockcycles.ifsck,bck,andlrckareprovidedcontinuouslyafterthissuspendedcondition,这
internaloperationisresynchronizedautomaticallywithinaperiodoflessthan3/f
S
.externalresettingisnot
必需的.
thepcm1780/82supportsindustry-standardaudiodataformats,includingright-justified,i
2
s,andleft-justified.
ThePCM1781supportsI
2
sand16-位-文字,正确的-justified.thedataformatsareshowninfigure22.数据
formatsareselectedforthepcm1780/82usingtheformatbits,fmt[2:0],locatedincontrolregister20,andare
selectedforthepcm1781usingthefmtpin.thedefaultdataformatis24-位,left-justified.allformatsrequire
binary2scomplement,msb-firstaudiodata.figure23showsadetailedtimingdiagramfortheserialaudio
接口.
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