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iX-1-9
IX
USB
transaction
This macro hardware executes transactions while its interface provides the firmware with utilities for executing
transactions. The interface to the firmware is implemented through control and status registers as well as
the interrupt signal which is asserted depending on the status. For settings that enable asserting interruption
according to the status, see the section on register description.
The macro issues a status to the firmware for each transaction. However, the firmware does not always have
to control respective transactions. The macro references the FIFO when responding to a transaction and
determines if data transfer is possible based on the number of data or vacancies to automatically handle the
transaction.
For example, for an OUT endpoint, the firmware can smoothly and sequentially process OUT transactions by
reading data from the FIFO region via either the Port interface (EPa, EPb, EPc, EPd) or the CPU interface (EP0,
EPa, EPb, EPc, EPd) to create a space in the FIFO region. On the other hand, for an IN endpoint, the firmware
can smoothly and sequentially process IN transactions by writing data in the FIFO region via either the Port
interface (EPa, EPb, EPc, EPd) or the CPU interface (EP0, EPa, EPb, EPc, EPd) to create valid data.
Table IX.1.4.1.3 lists control items and statuses related to transaction control on the EP0 endpoint.
TableIX.1.4.1.3ControlItemsandStatusesforEndpointEP0
Register/bit
EP0Control.INxOUT
EP0Control.ReplyDescriptor
EP0ControlIN.EnShortPkt
EP0ControlIN.ToggleStat,
EP0ControlOUT.ToggleStat
EP0ControlIN.ToggleSet,
EP0ControlOUT.ToggleSet
EP0ControlIN.ToggleClr,
EP0ControlOUT.ToggleClr
EP0ControlIN.ForceNAK,
EP0ControlOUT.ForceNAK
EP0ControlIN.ForceSTALL,
EP0ControlOUT.ForceSTALL
EP0ControlOUT.AutoForceNAK
MainIntStat.RcvEP0SETUP
EP0IntStat.IN_TranACK,
EP0IntStat.OUT_TranACK,
EP0IntStat.IN_TranNAK,
EP0IntStat.OUT_TranNAK,
EP0IntStat.IN_TranErr,
EP0IntStat.OUT_TranErr
Description
Setsthetransferdirectionatthedataandstatus
stages.
Activatesautomaticdescriptorreturn.
Enablestransmissionofshortpacketsthatareunder
themaximumpacketsize.Thissettingisclearedafter
theINtransactionthathastransmittedashortpacket
iscompleted.
Indicatesthestateofthetogglesequencebit.
ThissettingisautomaticallyinitializedbytheSETUP
stage.
Setsthetogglesequencebit.
Clearsthetogglesequencebit.
ReturnsaNAKresponsetoINorOUTtransactions
regardlessofthenumberofdataorvacanciesinthe
FIFOregion.
ReturnsaSTALLresponsetoINorOUTtransactions.
SetstheEP0Control.ForceNAKbitwheneveranOUT
transactioniscompleted.
IndicatesthataSETUPtransactionisexecuted.
Indicatestheresultofthetransaction.
item
Transactiondirection
Enabledescriptorreturn
Enableshortpacket
transmission
Togglesequencebit
Settoggle
Cleartoggle
ForcedNAKresponse
STALLresponse
SetautomaticForceNAK
SETUPreceptionstatus
Transactionstatus