Filter
Top Products
www.ti.com
2.10.7ReceiveFrameClassification
2.10.8PromiscuousReceiveMode
PeripheralArchitecture
Receivedframesareproper(good)frames,iftheyarebetween64bytesandthevalueinthereceive
maximumlengthregister(RXMAXLEN)bytesinlength(inclusive)andcontainnocode,align,orCRC
errors.
Receivedframesarelongframes,iftheirframecountexceedsthevalueinRXMAXLEN.TheRXMAXLEN
reset(default)valueis5EEh(1518indecimal).Longreceivedframesareeitheroversizedorjabber
frames.Longframeswithnoerrorsareoversizedframes;longframeswithCRC,code,oralignment
errorsarejabberframes.
Receivedframesareshortframes,iftheirframecountislessthan64bytes.Shortframesthataddress
matchandcontainnoerrorsareundersizedframes;shortframeswithCRC,code,oralignmenterrorsare
fragmentframes.Iftheframelengthislessthanorequalto20,thentheframeCRCispassed,regardless
ofwhethertheRXPASSCRCbitissetorclearedinthereceivemulticast/broadcast/promiscuouschannel
enableregister(RXMBPENABLE).
AreceivedlongpacketalwayscontainsRXMAXLENnumberofbytestransferredtomemory(ifthe
RXCEFENbitissetinRXMBPENABLE),regardlessofthevalueoftheRXPASSCRCbit.Followingisan
examplewithRXMAXLENsetto1518:
•Iftheframelengthis1518,thenthepacketisnotalongpacketandthereare1514or1518bytes
transferredtomemorydependingonthevalueoftheRXPASSCRCbit.
•Iftheframelengthis1519,thereare1518bytestransferredtomemoryregardlessofthe
RXPASSCRCbitvalue.ThelastthreebytesarethefirstthreeCRCbytes.
•Iftheframelengthis1520,thereare1518bytestransferredtomemoryregardlessofthe
RXPASSCRCbitvalue.ThelasttwobytesarethefirsttwoCRCbytes.
•Iftheframelengthis1521,thereare1518bytestransferredtomemoryregardlessofthe
RXPASSCRCbitvalue.ThelastbyteisthefirstCRCbyte.
•Iftheframelengthis1522,thereare1518bytestransferredtomemory.Thelastbyteisthelastdata
byte.
WhenthepromiscuousreceivemodeisenabledbysettingtheRXCAFENbitinthereceive
multicast/broadcast/promiscuouschannelenableregister(RXMBPENABLE),nonaddressmatchingframes
thatwouldnormallybefilteredaretransferredtothepromiscuouschannel.Addressmatchingframesthat
wouldnormallybefilteredduetoerrorsaretransferredtotheaddressmatchchannelwhentheRXCAFEN
andRXCEFENbitsinRXMBPENABLEareset.Aframeisconsideredtobeanaddressmatchingframe
onlyifitisenabledtobereceivedonaunicast,multicast,orbroadcastchannel.Framesreceivedto
disabledunicast,multicast,orbroadcastchannelsareconsiderednonaddressmatching.
MACcontrolframesaddressmatchonlyiftheRXCMFENbitinRXMBPENABLEisset.TheRXCEFEN
andRXCSFENbitsinRXMBPENABLEdeterminewhethererrorframesaretransferredtomemoryornot,
buttheydonotdeterminewhethererrorframesareaddressmatchingornot.Shortframesareaspecial
typeoferrorframes.
AsinglechannelisselectedasthepromiscuouschannelbytheRXPROMCHbitinRXMBPENABLE.The
promiscuousreceivemodeisenabledbytheRXCMFEN,RXCEFEN,RXCSFEN,andRXCAFENbitsin
RXMBPENABLE.Table4showstheeffectsofthepromiscuousenablebits.Properframesareframes
thatarebetween64bytesandthevalueinthereceivemaximumlengthregister(RXMAXLEN)bytesin
lengthinclusiveandcontainnocode,align,orCRCerrors.
SPRU941A–April2007EthernetMediaAccessController(EMAC)/41
ManagementDataInput/Output(MDIO)
SubmitDocumentationFeedback