howard wusb protocol

8/13/2019 Howard WUSB Protocol

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Wireless USB Protocol

John S. HowardSenior Architect

Intel Corporation


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2

AgendaAgenda

Protocol Components Data Transfers (general model)

Device Notifications Flow Control


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3

Wireless USB Channel

Review

Wireless USB Channel

Review

MM

C

MM

C

MM

C

MM

C

MM

C

MM

C

MM

C

MM

C

MM

C

MM

CWireless USB Channel

DRP

WUSB

DRP

WUSB

DRP

WUSB

DRP

WUSB

DRP

WUSB

DRP

WUSB

BeaconPeriod

Beacon

Period

t=0

Superframe n Superframe n+1

t=0 t=0

BeaconPeriod

WiMedia

MAC

WiMedia Physical Layer

Channel Time

The Wireless USB Channel is encapsulated by the WiMedia channel

Wireless USB channel is continuous sequence of linked control packetstransmitted by the Host during reserved WiMedia channel time

WUSB time is reserved from WiMedia channel time (DRPs)

Called MMCs Micro-schedule Management Commands

All Wireless USB Data communications are over the Wireless USB Channel


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Packet LayoutPacket Layout

WiMedia MAC Packet format

Utilizes Secure frame format

PLCP PreamblePHY

Header

MAC

HeaderHCSPayload

Variable Length: Z or more bytes

Pad

Bits

Tail

Bits

Tail

Bits FCS

12 OFDM Symbol sN * 6 OFDM Symbols

lsbmsb

Application Payload

(Variable Length: 0 to MaxPacketSize)

WUSB

Hdr

(2)

bmAttributes

(1)

bmStatus

(1)

MIC

(8)

Cypher Text

(Encrypted Data)

Frame

Control (2)

DestID

(2)

SrcID

(2)

Seq. Control

(2)

Acc Info

(2)

Endpoint Number [3:0]

Packet ID [6:4]

TKID

(3)

SFN

(6)

Non-secure Packet

Format

Secure Packet

Format

Rsrvd

(1)

Encrypt

Offset (2)

Type [ 8: 6] Del iver y Id ent/Control Frame Subtype [12: 9](011B) Data Frame [12] = 1B; [11:9] = Stream Index

(001B) Control Frame [12:9] = Application Defined Control Value

30 OFDM Symbo ls

Isochronous Header(3)

Isochronous Segment0

Isochronous Segment1

Isochronous SegmentbNumIsoSegments-1

Isochronous

Packet Format

bNumIsoSegments (1)

wPresentationTime (2)

wLength (2)

Segment Data (wLength)


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Wireless USB ChannelWireless USB Channel

MMC plus timetill next MMC

Basicstructure used tomaintain Wireless USB Channel

MMC

HD

R

Next MMC Time

MMC

Transaction Group

Information

Elements HD

R

Channel Time Dynamically Allocated for Data Communications

Between the Host and Devices in its Wireless USB Cluster


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Transaction Group

Slot Durations

Transaction Group

Slot Durations

Slot time durations are derived from adjacent

WXCTA blocks OUTs device know when they can stop listening

INs devices transmit what was requested

EOL WXCTA is always required to be present

MMC

WXCTA[0]

HDR

Next MMC Time

Attributes

Endpoint Info

FlagsSlot Type

Start Time

Type-Specific

Start Time [0]

MMC

HDR

WCTA_

IEH

eader

WXCTA[1]

WXCTA

[EOL]

Transaction Group

ProtocolTime

Slot [0]

Attributes

Endpoint Info

FlagsSlot Type

Start Time

Type-Specific

Start Time [1]

ProtocolTime

Slot [1]


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8

Time Slot AllocationsTime Slot Allocations

Three types of time slots:

WDRCTA (Device Receive)

WDT

CTA (Device Transmit)

WDNTSCTA(Device Notification) time slot

MMC

W_C

TAHDR

W

DRCTA

WDNTSCTA

W

DTCTA

WDRCTA WDNTSCTA WDTCTA

MMC


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Time Slot Allocations [cont.]Time Slot Allocations [cont.]

WDRCTA, WDTCTAs are used for Transaction Protocol

Control, Bulk, Interrupt and Isochronous data streams

Access is : guaranteed time slot

Schedule based on client application data flow needs

WDNTSCTAs used to emulate USB signaling events

Connect, disconnect, etc.

Access is : contention based - Slotted Aloha

Host schedules sufficient number of slots to provideadequate service for the cluster


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Transaction Group

Protocol Synchronization

Transaction Group

Protocol Synchronization

MMC

(n-1)preamble

t=0

Scheduled Time Slots in MMC

MMC

(n)preamble

t=0

TS[0] TS[1] TS[2] TS[3] TS[4]

Slot start time

according toDevices local

clocktGUARDTIME

Time at which a

Receiver must belistening before

the

slot start time Transmitter could

begin transmittinganywhere in this

window

(tMAXDRIFT )

tG UARDTIME

Time at which a

receiver must be

listening before

the scheduled

start of the MMC(MMC(n-1)

NextMMC)

MMC start time

according toDevices local

clock

Host could begin

transmitting

MMC(n) anywherein this window

(tMAXDRIFT )


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Transaction Group

Protocol Synchronization (cont.)

Transaction GroupProtocol Synchronization (cont.)

PLCP Preamble PLCP Header

Sync Delay

t0

PHY_ACTIVE

Radio Medium

24 OFDM Symbols

30 OFDM Symbols

t0 is the time of the first symbol of the MMCs

preamble

Devices can calculate this from the edge ofPHY_ACTIVE


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12

Time Slot Scheduling

Requirements

Time Slot Scheduling

Requirements

MMC

TS[0] TS[1] TS[2] TS[4]

MMC

Host Transmitted Packets Device Transmitted Packets

MMC PHY Hdr StandardPreamble

dataStandard

PreamblePHY Hdr

tINTERSLOTTIME Data Packetfor TS[0]

Data Packetfor TS[1]

dataStandard

Preamble PHY HdrtBUSTURNINTERSLOTT IMEData Packet

for TS[2]

dataStandard

PreamblePHY Hdr

MMC

Packet

TS[3]

dataStandard

PreamblePHY Hdr Data Packet

for TS[3]

tBUSTURNI NTERSLOTTIMEE

The first packet transmitted in a protocoltime slot must have a standard preamble

t INTERSLOTTIME+

tGUARDTIME

t INTERS LOTTIME


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Data Burst TimingData Burst Timing

MMC to first Data OUT :MIFS (1.875 s)

MMC to first Data IN :Bus Turn Time

Bus Turn + Guard Time

(SIFS + 1s) (11 s)

IPGs between burst packetsis fixed (MIFS)

First packet Preamble mustbe Standard Length

Host determines subsequent

preamble to use

MMC

OUT Data Phase Time Slot

Standard

PreamblePHY Hdr data

Short /Std

PreamblePHY Hdr data

MMC

IN Data Phase Time Slot

Standard

Preamble

PHY Hdr dataShort/Std

Preamble

PHY Hdr data

tINTERSLOTTIME

tBUSTURNINTERSLOTTIME

tSTREAMIPGtSTREAMIPG


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14

AgendaAgenda

Protocol Components Data Transfers (general model)



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Data Stream Synchronization

Basic Model

Data Stream SynchronizationBasic Model

Protocol-level support forreliable data delivery

Identifies:

Data orderingrequirements

Guarantees advancementof data stream only afterreliable data delivery

Terms: Maximum Burst Size

Maximum Sequence

Maximum SequenceDistance

Transmitter sends data packets associated

with Transmit window Sequence numbers Receiver acknowledges with new receive

window (what is available now)

Protocol rules for recovering lost packets,avoiding sequence range wrap, etc.

See Bursting Session

Transmit

Window

Receive

Window

01

2

3

45

6

7

8

90

1

2

3

45

6

7

8

9

Data Packet Burst(S0, S1, S2, S3)

0 1

2

3

456

7

8

9Acknowledgement

(0011110000 B)

01

2

3

45

6

7

8

9


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Transaction Transmit Bit RateTransaction Transmit Bit Rate

MMCs are transmitted at base signaling rate (53.3 Mb/s)

Host dictates transmit bit rate for data and handshakephase transmissions

Transmit bit rate applies to entire phase

OUTs : host uses only TBRs supported by device (assumesTx/Rx symmetry)

INs : WDTCTA.PHY_TXRate directs which TBR device mustuse during protocol time slot

Handshakes: Host must use base signaling rate for a handshake time slot

(OUTs)

Host must ensure a data phase time slot is always large enough toaccommodate a handshake transmitted at base signaling rate


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Transaction Format

General Model

Transaction FormatGeneral Model

WDT

CTA

DATA(Seq# N)

DATA

(Seq# N+1)

...DATA

(Seq# N+Y)

HNDSKNAK or

STALL

MMC

bvDINAck

HDR

WDTCTAMMC HDR

Data not Ready, or Internal Error

Number of packets in

data phase depends onTransaction Burst Size

or available data.The next Sequence

number is always

derived (N+1) moduloMaxSequence.

Smashed MMC

DataINPhaseDataPackets

WDR

CTA

DATA(Seq# N)

DATA

(Seq# N+1)

...DATA

(Seq# N+Y)

HNDSKACK (bvAckCode)

or NAK or STALL

HDR

Smashed MMC

D

ataOUTPhaseDataPack

ets

WDT

CTA

Idle

Idle

IN OUT

Token

Data

Handshake

Idle

Direction = IN = 1bvDINAck

PHY_TXRate

Direction = OUT = 0


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Data IN Transfer

Streaming Example

Data IN TransferStreaming Example

MMC

Data (S0)

Transaction Group N Transaction Group N + 1

MMC

WDTCTA

(TokenI)

HDR

Data (S1)

WDTCTA

(TokenI)

HDR

TokenI .bvDINAcK =001HTokenI.bvDINAcK=002H

Transaction 1

Transaction 0 Transaction 2

WDT

CTA (IN)

bvDINAck = 001H

DATA(S0)

(Use Data)

WDT

CTA (IN)

bvDINAck = 002H

DATA(S1)

(Use Data)

WDT

CTA (IN)

bvDINAck = 001H

MMC Device EP TX MMC Device EP TX Host TX (MMC)


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Data IN Transfer

End Of Transfer Example

Data IN TransferEnd Of Transfer Example

MMC

Data (S1)


MMC

WDTCTA

(TokenI)

HDR

WDTCTA

(TokenI)

HDR

bvDINAcK=002H

Blank WDTCTA

BlanK.wStart = NextWxCTA.wStart

TokenI.bvDINAcK=000H

WDTCTA

EOL

Transaction N

Transaction N-1

WDT

CTA (IN)

bvDINAck = 002H

DATA(S1)

(Use Data)

Blank WDT

CTA (IN)bvDINAck = 000HwStart = NextWxCTA.wStart

End of List WxCTA (EOL)

MMC Device EP TX MMC


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Data IN Transfer

Short Packet Example

Data IN TransferShort Packet Example

MMCData (S0)


MMC

WDTCTA

(TokenI)

HDR

WDTCTA

(TokenI)

HDR

TokenI .bvDINAcK=001HTokenI.bvDINAcK=002H

LastPacketFlag = 1B

Blank WDTCTA

Transaction 1

Transaction 0

WDT

CTA (IN)bvDINAck = 001H

DATA(S0)LastPacketFlag = 1

(Use Data)

WDT

CTA (IN)bvDINAck = 002H

MMC Device EP TX MMC

Host may commence next transfer immediately (if buffer available)


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21

Data OUT Transfers

Streaming Example

Data OUT TransfersStreaming Example

MMC

WDRCTA

(TokenO)

HDR

WDTCTA

(HndskO) Data (S0) AcK

MMC

WDRCTA

(TokenO)

HDR

WDTCTA



bvAckCode

10BbvAckCode

01B

Token Phase Data Phase Handshake Phase

Transaction 1

Transaction 0

WDR

CTA (OUT)

WDT

CTA (Handshake)

DATA(0)

(Use Data)

HNDSHK

bvAckCode = 02H

WDR

CTA (OUT)

WDT

CTA(Handshake)

DATA(1)

(Use Data)

HNDSHK

bvAckCode = 01H

Host TX (MMC) Host TX Device EP TX Host TX (MMC) Host TX Device EP TX


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Data OUT Transfers

Short Packet Example

Data OUT TransfersShort Packet Example

MMC

WDRCTA

(TokenO)

HDR

WDTCTA


MMC

HDR


bvAckCode

002 H

LastPacketFlag = 1

Transaction 1

Transaction 0

WDR

CTA (OUT)

WDT

CTA (Handshake)

DATA(0)LastPacketFlag = 1

(Use Data)

HNDSHKbvAckCode = 02H

Host TX (MMC) Host TX Device EP TX Host TX (MMC)

Host may commence next transfer immediately (if data available)


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Control Transaction Format

Setup Stage w/Data Stage

Control Transaction FormatSetup Stage w/Data Stage

WDTCTA

DATA

(Seq# 0)HNDSK

NAK or

STALL

MMC

bvDINAck

HDR

WDTCTAMMC HDR

Data not Ready, or Bad Command

SmashedMMC

DataINPhase

DataPacket

Idle

Setup + first IN Data Stage

transaction

Token

w/Setup

Data

Handshake

Idle

Setup Bytes

Setup Flag = 1B

ControlStatusFlag= 0B

Direction = IN = 1PHY_TXRate

bvDINAck= 001H

WDRCTAMMC HDR

SmashedMMC

DataOUTPhase

DataPacket

Idle

Setup + first OUT Data Stage

transaction

Setup Bytes

HNDSKACK (bvAckCode)or NAK or STALL

WDTCTA

DATA

(Seq# 0)

Setup Flag = 1B

Direction = OUT = 0Direction = OUT = 0B


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Control Transaction FormatSetup w/No Data Stage; Bare Status Stage

Control Transaction FormatSetup w/No Data Stage; Bare Status Stage

Setup + No Data Stage

Token

Data

Handshake

Idle

WDTCTA

HNDSK

ACK or

NAK orSTALL

MMC HDR

SmashedMMC

Idle

Setup Bytes WDTCTA

HNDSK

ACK or

NAK orSTALL

MMC HDR

Sma

shedMMC

Idle

Status Stage

Setup Flag = 1B

ControlStatusFlag= 1BDirection = IN = 1

Setup Flag = 0B

ControlStatusFlag= 1B

Direction = IN = 1


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25

Control TransferExample (Set Address - No Data Stage)

Control TransferExample (Set Address - No Data Stage)

MMC

WDTC

TA

(Status

Stage)

HDR

Setup

Bytes

(8)

HandshakeMMC

ETC

.

HDR

Transaction Group N Transaction Group N+1

Status Stage - Handshake

Status StageSetup Stage

Transaction 0

WDT

CTA

SetupFlag = 1BCtrl/StatusFlg = 1B(Handshake)

Setup Bytes (8) set address

HNDSHK

Hndshk code = ACKbvAckCode = 00HDirection = IN

Host TX (MMC)

Setup Stage Status Stage

Host TX (MMC) Device EP TX


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26

Control TransferExample (Control Write - SetKey)

Control TransferExample (Control Write - SetKey)


Data OutSeq = 0B(Set Key)

WDT

CTASetupFlag = 0BCtrl/StatusFlag = 1B(Handshake)

HNDSHKHndshk code = ACKbvAckCode = 00HDirection = IN

Host TX Device EP TX

Setup Stage Data Stage Status Stage

Host TX (MMC)

WDR

CTASetupFlag = 1BCtrl/StatusFlag = 0B(Handshake)

Setup Bytes (8) set Key

WDT

CTA - handshake

HNDSHKHndshk code = ACKbvAckCode = 02H


MMC

WDRCT

A

(TokenO)

HDR

Setup Bytes (8)

Data (seq = 0)

Length = Y

Transaction GroupN TransactionGroup N+1

Std. Out Transaction

AcK

MMC

WDTCT

A

(StatusS

tg)

HDR

HNSK

MMC

ETC.

HDR

Data Stage Status Stage

Transaction GroupN+2

ControlStatusFlag= 1

Setup Stage

WDTCT

A

(HndskO)

Handshake Transaction

Setup Flag = 1


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Control Transfer(Control Write SetKey lost data packet)

Control Transfer(Control Write SetKey lost data packet)

MMC

WDTCTA

(Token

I)

HDR

Setup Bytes (8)

Data (seq = 0)

Length = Y

Transaction Group N Transaction

Group N+1


AcK

MMC

WDTCT

A

(StatusS

tg)

HDR

HNSK

MMC

ETC.

HDR

Data Stage Status Stage

Transaction Group N+2

ControlStatusFlag = 1

Setup Stage

WDTCT

A

(HndskO)


Setup Flag = 1

bvAckCode = 001H

MMC

WDRCT

A

(TokenO)

HDR

Data (seq = 0)

Length = Y


AcK

WDTCTA

(HndskO)

bvAckCode = 002H

X


WDR

CTA

SetupFlag = 1BCtrl/StatusFlag = 0B(Handshake)

Setup Bytes (8) set Key

WDT

CTA - handshake

Data Out

Seq = 0B(Set Key)

WDR

CTA

SetupFlag = 0BCtrl/StatusFlag = 0B

WDT

CTA - handshake

Data Out

Seq = 0B(Set Key

HNDSHK

Hndshkcode = ACKbvAckCode= 02H

Host TX Device EP TX

Setup Stage Data Stage

Host TX Host TX (MMC)

HNDSHK

Hndshk code = ACKbvAckCode = 01H



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Control TransferExample (Control Read Get Descriptor)


MMC

WDTCTA

(Token

I)

HDR

Setup

Byte

s

Data (seq = 0)

Length=Y

Transaction Group N Transaction Group N+1

Std. IN Transaction

MMC

WDTCTA

(StatusStg)

HDR

bvDINAcK = 002H

Data StageStatus Stage


Setup

Stage

HNSKMMC

ETC.

HDR

StatusStageFlag = 1SetupFlag = 1


Data INSeq = 1B(Get Descriptor Data)

WDT

CTASetupFlag = 0BCtrl/StatusFlag = 1BbvDINAck = 002H(Handshake)

HNDSHKHndshk code = ACKbvAckCode = 00HDirection = IN

Status Stage

Device EP TX Device EP TX

Setup Stage Data Stage

Host TX (MMC)

WDT

CTASetupFlag = 1BCtrl/StatusFlag = 0BbvDINAck = 001H

Setup Bytes (8)Get Descriptor

Host TX (MMC)

C l T f


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Data packet gets smashed

Host will retry Data Stage

If device saw Setup,

will respond

with Data

If device did not see

a Setup, willrespond with STALL

MMC

WDTCTA

(StatusStg)

HDR

bvDINAcK = 002H


HNSKMMC

ETC.

HDR

StatusStageFlag = 1

MMC

WDTCTA

(TokenI)

HDR

Se

tupBytes

Data (seq = 0)

Le

ngth

=

Y

Std. IN Transaction

MMC

W

DTCTA

(StatusStg)

HDR

bvDINAcK = 002H


HNSKMMC

ETC.

HDR

StatusStageFlag = 1

SetupFlag = 1

X

MMC

W

DTCTA

(T

okenI)

HDR

Data (seq = 0)

MMC

WDTCTA

(TokenI)

HDR

HNSK (STALL)MMC

WDTCTA

(TokenI)

HDR

Setup

Bytes

Data (seq = 0)


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AgendaAgenda

Packet Layouts

Transaction Groups

Timing Constraints Data Transfers (general model)


D i N tifi ti Ti Sl tD i N tifi ti Ti Sl t


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Device Notifications Time SlotsDNTS

Device Notifications Time SlotsDNTS

Devices are only allowed transmitters

Device notification messages (to the WUSBHost) are only allowed data communications

Nature of notification messages are that theyare asynchronous and infrequent

Fixed Maximum Size for notification messages

Take advantage of this in the access method

Host policy to manage efficiently

Unused time is just lost to WUSB data stream

DNTS Access MethodDNTS Access Method


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DNTS Access Method

Contention Based : Slotted Aloha

DNTS Access Method

Contention Based : Slotted Aloha

Fixed (maximum) sizedmessage

DNTS is a window of uniformsized message slots

WDNTSCTA indicatesnumber of message slots

Device selects a message

slot using a uniformlydistributed random integervalue (in range 1 to N)

Device transmits messagea message slot start time

MMC

W

DNTSCTA

1 2 3 N

DNTS CTA Start

# Slots (N)

Slot Select = uniform(1, N)

D i N tifi tiDe ice Notifications


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Device NotificationsReliability

Device NotificationsReliability

Protocol for Device Notifications isdesigned for unreliability:

Notification(s)

Host Response

Device Continues to send

Notifications until it observes HostResponse

Device Response

Host will cease response

when it observes follow-up

device response (when

applicable)

Host must tolerate

retransmissions of

notification that occur

while it is responding

Device must

tolerate Host

response

retransmissions

D i N tifi tiDevice Notification


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Device NotificationExample (Device Perspective) - Connect

Device NotificationExample (Device Perspective) - Connect

Sending

Notification

Receive

MMC [ConnectAck_IE [MyCDID, DeviceAddress] []]

UnConnected

Connected

Transmit

(DN_Connect, Self-Beaconing, MyCDID)

Initiate Connect

Wait For

Connect ACK

Xmit

Notification

DNTS Available

Connect

Ack


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AgendaAgenda

Packet Layouts

Transaction Groups

Timing Constraints Data Transfers (general model)



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Flow ControlFlow Control

Used on All transfer types

Device provides flow-control information in its response to the host

bmStatus field in the WUSB Header of a Data, IData or Handshake

OUTs, the flow control response is in the AcK handshake

INs, the flow control response is in the Data(x) packet

Handshake encoded with NAKs always available

Flow control status from Endpoint results in removal of endpointfrom Active schedule

Resumption of service to a flow-controlled endpoint depends

on transfer type Bulk & Control

Device delivers a Endpoint Ready (DN_EPRdy) notification to the hostduring an DNTS

Interrupt & Isochronous Next service interval

Control TransferControl Transfer


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Control TransferExample (Control Read Flow Control)

Control TransferExample (Control Read Flow Control)

Data Stage (cont.)

MMC

WDTCT

A

(Token

I)

HDR

Setup

Bytes

Data (seq = 0)

Length=Y

Transaction Group N Transaction Group Y

Std. IN Transaction

MMC

WDTCT

A

(StatusS

tg)

HDR

bvDINAcK = 002H

Data Stage

Status Stage


Setup

Stage

HNSKMMC

ETC.

HDR

StatusStageFlag = 1SetupFlag = 1

HNSK

NAK

MMC

WDTCT

A

(Token

I)

HDR

MMC

WDNTSCTA

HDR

DN_

EPRdy

Transaction Group Z Transaction Group Z+1

Host stops polling endpoint on NAK

Device notifies it is ready with DN_EPRdy

Host resumes polling endpoint

Retries data phase transaction in this example


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