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3.3HCCommandandStatusRegister(HCCOMMANDSTATUS)
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Registers
TheHCcommandandstatusregister(HCCOMMANDSTATUS)showsthecurrentstateofthehost
controllerandacceptscommandsfromthehostcontrollerdriver.HCCOMMANDSTATUSisshownin
Figure4anddescribedinTable4.
Figure4.HCCommandandStatusRegister(HCCOMMANDSTATUS)
31181716
ReservedSOC
R-0R-0
1543210
ReservedOCRBLFCLFHCR
R-0R/W-0R/W-0R/W-0R/W-0
LEGEND:R/W=Read/Write;R=Readonly;-n=valueafterreset
Table4.HCCommandandStatusRegister(HCCOMMANDSTATUS)FieldDescriptions
BitFieldValueDescription
31-18Reserved0Reserved
17-16SOC0-3hSchedulingoverruncount.Countsthenumberoftimesaschedulingoverrunoccurs.Thiscountis
incrementedevenifthehostcontrollerdriverhasnotacknowledgedanypreviouspendingscheduling
overruninterrupt.
15-4Reserved0Reserved
3OCR0-1Ownershipchangerequest.Thehostcontrollerdriversetsthisbittogainownershipofthehost
controller.TheprocessordoesnotsupportSMIinterrupts,sonoownershipchangeinterruptoccurs.
2BLF0-1Bulklistfilled.ThehostcontrollerdrivermustsetthisbitifitmodifiesthebulklisttoincludenewTDs.If
theHCcurrentbulkregister(HCBULKCURRENTED)is0,theUSBhostcontrollerdoesnotbegin
processingbulklistEDsunlessthisbitisset.WhentheUSBhostcontrollerseesthisbitsetandbegins
processingthebulklist,itclearsthisbitto0.
1CLF0-1Controllistfilled.Thehostcontrollerdrivermustsetthisbitifitmodifiesthecontrollisttoincludenew
TDs.IftheHCheadcontrolregister(HCCONTROLHEADED)is0,theUSBhostcontrollerdoesnot
beginprocessingcontrollistEDsunlessthisbitisset.WhentheUSBhostcontrollerseesthisbitset
andbeginsprocessingthecontrollist,itclearsthisbitto0.
0HCRHostcontrollerreset.
0Noeffect.
1InitiatesasoftwareresetoftheUSBhostcontroller.ThistransitionstheUSBhostcontrollertotheUSB
suspendstate.ThisresetsmostUSBhostcontrollerOHCIregisters.OHCIregisteraccessesmustnot
beattempteduntilareadofthisbitreturnsa0.Awriteof1tothisbitdoesnotresettheroothuband
doesnotsignalUSBresettodownstreamUSBfunctions.
SPRUFM8–September2008UniversalSerialBusOHCIHostController15
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