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1Introduction
1.1PurposeofthePeripheral
User'sGuide
SPRUFM8–September2008
UniversalSerialBusOHCIHostController
ThisdocumentdescribestheuniversalserialbusOHCIhostcontroller.
TheUSBOHCIhostcontroller(HC)isasingleportcontrollerthatcommunicateswithUSBdevicesatthe
USBlow-speed(1.5Mbit-per-secondmaximum)andfull-speed(12Mbit-per-secondmaximum)datarates.
ItiscompatiblewiththeUniversalSerialBusSpecificationRevision2.0andtheOpenHCI—OpenHost
ControllerInterfaceSpecificationforUSB,Release1.0a,availablethroughtheCompaqComputer
Corporationwebsite,andhereaftercalledtheOHCISpecificationforUSB.Itisassumedthatusersofthe
USBhostcontrollerarealreadyfamiliarwiththeUSBSpecificationandOHCISpecificationforUSB.
TheUSBhostcontrollerimplementstheregistersetandmakesuseofthememorydatastructures
definedintheOHCISpecificationforUSB.Theseregistersanddatastructuresarethemechanismsby
whichaUSBhostcontrollerdriversoftwarepackagecancontroltheUSBhostcontroller.TheOHCI
SpecificationforUSBalsodefineshowtheUSBhostcontrollerimplementationmustinteractwiththose
registersanddatastructuresinsystemmemory.
Toreduceprocessorsoftwareandinterruptoverhead,theUSBhostcontrollergeneratesUSBtraffic
basedondatastructuresanddatabuffersstoredinsystemmemory.TheUSBhostcontrolleraccesses
thesedatastructureswithoutdirectinterventionbytheprocessorusingitsbusmasterport.Thesedata
structuresanddatabufferscanbelocatedininternalorexternalsystemRAM.
TheUSBhostcontrollerprovidesaninterrupttoboththeARMandDSP.
SPRUFM8–September2008UniversalSerialBusOHCIHostController7
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