2.5.4TransmitBufferDescriptorFormat
Architecture
Atransmit(TX)bufferdescriptor(Figure7)isacontiguousblockoffour32-bitdatawordsalignedona
32-bitboundarythatdescribesapacketorapacketfragment.Example1showsthetransmitbuffer
descriptordescribedbyaCstructure.
Figure7.TransmitBufferDescriptorFormat
Word0
310
NextDescriptorPointer
Word1
310
BufferPointer
Word2
3116150
BufferOffsetBufferLength
Word3
3130292827262516
SOPEOPOWNEREOQTDOWNCMPLTPASSCRCReserved
150
PacketLength
Example1.TransmitBufferDescriptorinCStructureFormat
/*
//EMACDescriptor
//
//Thefollowing
istheformatofasinglebufferdescriptor
//ontheEMAC.
*/
typedefstruct_EMAC_Desc{
struct_EMAC_Desc*pNext;/*Pointertonextdescriptorinchain*/
Uint8*pBuffer;/*Pointertodatabuffer*/
Uint32BufOffLen;/*BufferOffset(MSW)andLength(LSW)*/
Uint32PktFlgLen;/*PacketFlags(MSW)andLength(LSW)*/
}EMAC_Desc;
/*PacketFlags*/
#defineEMAC_DSC_FLAG_SOP0x80000000u
#defineEMAC_DSC_FLAG_EOP0x40000000u
#defineEMAC_DSC_FLAG_OWNER0x20000000u
#defineEMAC_DSC_FLAG_EOQ0x10000000u
#defineEMAC_DSC_FLAG_TDOWNCMPLT0x08000000u
#defineEMAC_DSC_FLAG_PASSCRC0x04000000u
24EthernetMediaAccessController(EMAC)/ManagementDataInput/Output(MDIO)SPRUEQ6–December2007
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