MII设计详解.ppt

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1、MIIKadeHuangMIIMIIrelationshiptotheISO/IECOSIreferencemodelandtheIEEE802.3CSMA/CDLANmodelMIIsignalTX_CLK(transmitclock)RX_CLK(receiveclock)TX_EN(transmitenable)TXD(transmitdata)TX_ER(transmitcodingerror)RX_DV(ReceiveDataValid)RXD(receivedata)MIIsignalRX_ER(receiveerror)CRS(carriersense)COL(col

2、lisiondetected)MDC(managementdataclock)MDIO(managementdatainput/output)MIIsignalfunctionalspecifications1.TX_CLK(transmitclock)TX_CLK(TransmitClock)isacontinuousclockthatprovidesthetimingreferenceforthetransferoftheTX_EN,TXD,andTX_ERsignalsfromtheReconciliationsublayertothePHY.TX_CLKissourcedb

3、ythePHY.TheTX_CLKfrequencyshallbe25%ofthenominaltransmitdatarate±100ppm.100Mb/s->25M10Mb/s->2.5MThedutycycleoftheTX_CLKsignalshallbebetween35%and65%inclusive.2.RX_CLK(receiveclock)RX_CLKisacontinuousclockthatprovidesthetimingreferenceforthetransferoftheRX_DV,RXD,andRX_ERsignalsfromthePHYtotheR

4、econciliationsublayer.RX_CLKissourcedbythePHY.MIIsignalfunctionalspecificationsRX_CLKshallbesynchronouswithrecovereddata,shallhaveafrequencyequalto25%ofthedatarateofthereceivedsignal,andshallhaveadutycycleofbetween35%and65%inclusive.3.TX_EN(transmitenable)TX_ENisdrivenbytheReconciliationsublay

5、erItshallbeassertedbytheReconciliationsublayersynchronouslywiththefirstnibbleofthepreambleandshallremainassertedwhileallnibblestobetransmittedarepresentedtotheMIIMIIsignalfunctionalspecifications4.TXD(transmitdata)TXDisabundleof4datasignals(TXD<3:0>)thataredrivenbytheReconciliationsublayer.TXD

6、<3:0>shalltransitionsynchronouslywithrespecttotheTX_CLK.MIIsignalfunctionalspecifications5.TX_ER(transmitcodingerror)TX_ERshalltransitionsynchronouslywithrespecttotheTX_CLK.WhenTX_ERisassertedforoneormoreTX_CLKperiodswhileTX_ENisalsoasserted,thePHYshallemitoneormoresymbolsthatarenotpartoftheva

7、liddataordelimitersetsomewhereintheframebeingtransmitted.IfaReconciliationsublayerorarepeaterwithanMIIportdoesnotactivelydrivetheTX_ERsignal,itshallensurethattheTX_ERsignalispulleddowntoaninactivestateatalltimes.MIIsignalfunctionalspeci