5.28ReceiveChannel0-7FreeBufferCountRegister(RXnFREEBUFFER)
EthernetMediaAccessController(EMAC)Registers
Thereceivechannel0-7freebuffercountregister(RXnFREEBUFFER)isshowninFigure68and
describedinTable67.
Figure68.ReceiveChannelnFreeBufferCountRegister(RXnFREEBUFFER)
3116
Reserved
R-0
150
RXnFREEBUF
WI-0
LEGEND:R=Readonly;WI=Writetoincrement;-n=valueafterreset
Table67.ReceiveChannelnFreeBufferCountRegister(RXnFREEBUFFER)FieldDescriptions
BitFieldValueDescription
31-16Reserved0Reserved
15-0RXnFREEBUF0-FFhReceivefreebuffercount.Thesebitscontainthecountoffreebuffersavailable.The
RXFILTERTHRESHvalueiscomparedwiththisfieldtodetermineiflowpriorityframesshouldbe
filtered.TheRXnFLOWTHRESHvalueiscomparedwiththisfieldtodetermineifreceiveflow
controlshouldbeissuedagainstincomingpackets(ifenabled).Thisisawrite-to-incrementfield.
Thisfieldrollsoverto0onoverflow.
IfhardwareflowcontrolorQOSisused,thehostmustinitializethisfieldtothenumberofavailable
buffers(oneregisterperchannel).TheEMACdecrementstheassociatedchannelregisterforeach
receivedframebythenumberofbuffersinthereceivedframe.Thehostmustwritethisfieldwith
thenumberofbuffersthathavebeenfreedduetohostprocessing.
SPRUEQ6–December2007EthernetMediaAccessController(EMAC)/ManagementDataInput/Output(MDIO)109
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