May 16, 2000 2

USB 2.0 Test Modesand Their ApplicationUSB 2.0 Test Modes

and Their ApplicationJon LuekerJon Lueker

Intel CorporationIntel Corporation

May 16, 2000 3

Link Integrity StrategyLink Integrity Strategy

Define necessary and sufficient set of Define necessary and sufficient set of specifications for cables, upstream-facingspecifications for cables, upstream-facingports, and downstream-facing portsports, and downstream-facing ports

Define reproducible tests which allow testingDefine reproducible tests which allow testingof each element in isolationof each element in isolation

Define required test modes which allow testsDefine required test modes which allow teststo be performed with standardized equipmentto be performed with standardized equipmentand techniquesand techniques

May 16, 2000 4

Specifications for aHigh-Speed TransmitterSpecifications for aHigh-Speed Transmitter

Source impedanceSource impedance Clock frequencyClock frequency DC Levels into reference loadDC Levels into reference load Transmit eye pattern into reference loadTransmit eye pattern into reference load

– At pins of transceiver (guideline)At pins of transceiver (guideline)– At USB receptacle (if no captive cable)At USB receptacle (if no captive cable)– At end of cable (if cable is captive)At end of cable (if cable is captive)

Minimum allowable rise/fall timeMinimum allowable rise/fall time

May 16, 2000 5

Specifications for aHigh-Speed ReceiverSpecifications for aHigh-Speed Receiver

DC termination voltage and resistanceDC termination voltage and resistance Squelch threshold levelSquelch threshold level Disconnect threshold levelDisconnect threshold level TDR (AC loading) limitsTDR (AC loading) limits Worst case eye patterns which mustWorst case eye patterns which must

be recoverablebe recoverable– At pins of transceiver (guideline)At pins of transceiver (guideline)– At USB receptacle (if no captive cable)At USB receptacle (if no captive cable)– At end of cable (if cable is captive)At end of cable (if cable is captive)

May 16, 2000 6

Specifications for USB CableSpecifications for USB Cable

Maximum length and delay per meterMaximum length and delay per meter(delay spec added in USB 1.1 ECN)(delay spec added in USB 1.1 ECN)

Differential and common mode impedance Differential and common mode impedance (common mode spec added in ECN)(common mode spec added in ECN)

Skew (tightened to 100 ps from 400 ps in ECN)Skew (tightened to 100 ps from 400 ps in ECN) Maximum allowable loss (added 200MHzMaximum allowable loss (added 200MHz

and 400MHz points in ECN)and 400MHz points in ECN)

USB 1.1 cable specification was updated in November, 1999, to USB 1.1 cable specification was updated in November, 1999, to guarantee specs which were being met typically guarantee specs which were being met typically

May 16, 2000 7

Test ModesTest Modes

High-speed capable devices/hubs must support High-speed capable devices/hubs must support test modes test modes

Test modes enable repeatable testingTest modes enable repeatable testing SetFeature(TEST_MODE) and SetFeature(TEST_MODE) and

SetPortFeature(PORT_TEST) requests provide SetPortFeature(PORT_TEST) requests provide standard means of entering modestandard means of entering mode

Exit action is also standardizedExit action is also standardized– Upstream facing port – power cycleUpstream facing port – power cycle– Downstream facing port – hub resetDownstream facing port – hub reset

May 16, 2000 8

Test Mode Test_SE0_NAKTest Mode Test_SE0_NAK

Port enters and remains in the high-speedPort enters and remains in the high-speedidle state idle state

Regular actions, such as suspending,Regular actions, such as suspending,are inhibitedare inhibited

Upstream-facing ports must respond to anyUpstream-facing ports must respond to anyIN token packet with a NAK handshakeIN token packet with a NAK handshake(if CRC is correct)(if CRC is correct)

Allows Testing of Output Impedance (AC and DC), Allows Testing of Output Impedance (AC and DC), Termination Voltage, and Receiver SensitivityTermination Voltage, and Receiver Sensitivity

May 16, 2000 9

Test Modes Test_Jand Test_KTest Modes Test_Jand Test_K

Port enters and remains in the high-speedPort enters and remains in the high-speedJ or K state J or K state

Regular actions, such as suspending,Regular actions, such as suspending,are inhibitedare inhibited

Allows Testing of Output Voltage and Output Allows Testing of Output Voltage and Output Impedance When Each Output Is High or LowImpedance When Each Output Is High or Low

May 16, 2000 10

Test Mode Test_PacketTest Mode Test_Packet

Port repetitively transmits defined test packetPort repetitively transmits defined test packet Packet is designed to contain the full range of Packet is designed to contain the full range of

pattern frequencies and duty factorspattern frequencies and duty factors

Allows Testing of Output Eye Patterns, Jitter, Allows Testing of Output Eye Patterns, Jitter, Waveform Parameters, and FrequencyWaveform Parameters, and Frequency

May 16, 2000 11

Test Mode Test_Force_EnableTest Mode Test_Force_Enable

Applies only to downstream–facing hub portsApplies only to downstream–facing hub ports Required behaviors apply even if no deviceRequired behaviors apply even if no device

is attachedis attached Port must be enabled in high-speed modePort must be enabled in high-speed mode Downstream packets must be repeated to the portDownstream packets must be repeated to the port

Allows Testing of Disconnect ThresholdAllows Testing of Disconnect Threshold

May 16, 2000 12

Example: Testing aSelf-Powered DeviceExample: Testing aSelf-Powered Device

Testing Input Impedance and Termination VoltageTesting Input Impedance and Termination Voltage Testing Output LevelsTesting Output Levels Testing Transmit WaveformsTesting Transmit Waveforms Testing Receiver SensitivityTesting Receiver Sensitivity Testing Squelch ThresholdTesting Squelch Threshold

May 16, 2000 13

Example: Testing Input Impedance and Termination VoltageExample: Testing Input Impedance and Termination Voltage

1.1. Attach DUT to USB 2.0 host controllerAttach DUT to USB 2.0 host controller

2.2. Reset the device and then issue request to place Reset the device and then issue request to place device in Test_SE0_NAK modedevice in Test_SE0_NAK mode

3.3. Unplug cable from device and replace it with test Unplug cable from device and replace it with test cable/fixturecable/fixture

4.4. Measure DC output voltage on each lineMeasure DC output voltage on each line

5.5. Measure DC resistance on each lineMeasure DC resistance on each line

6.6. Perform differential TDR test on outputsPerform differential TDR test on outputs

May 16, 2000 14

Example: TestingOutput LevelsExample: TestingOutput Levels

1.1. Attach DUT to USB 2.0 host controllerAttach DUT to USB 2.0 host controller

2.2. Reset the device and then issue request to place Reset the device and then issue request to place device in Test_J modedevice in Test_J mode

3.3. Unplug cable from device and replace it with test Unplug cable from device and replace it with test cable/fixturecable/fixture

4.4. Measure output voltages into 45 Ohm loadsMeasure output voltages into 45 Ohm loadsto groundto ground

5.5. Repeat using Test_KRepeat using Test_K

May 16, 2000 15

Eye Pattern Test FixtureEye Pattern Test Fixture

Transmitter Test Attenuation:Transmitter Test Attenuation: Voltage at Scope Inputs = Voltage at Scope Inputs = 0.760 * Voltage at Transmitter Outputs0.760 * Voltage at Transmitter Outputs

Receiver Test Attenuation:Receiver Test Attenuation: Voltage at Receiver Inputs = Voltage at Receiver Inputs = 0.684 * Voltage at Data Generator Outputs0.684 * Voltage at Data Generator Outputs

Transmitter/Receiver Test FixtureTransmitter/Receiver Test Fixture

VbusVbus

D+ D+

D- D-

GndGnd

VbusVbus

D+ D+

D- D-

GndGnd

15.8 Ohms15.8 Ohms ++To 50 Ohm Inputs of aTo 50 Ohm Inputs of aHigh Speed DifferentialHigh Speed Differential

Oscilloscope, or 50 OhmOscilloscope, or 50 Ohm Outputs of a High Speed Outputs of a High Speed

Differential Data Generator Differential Data Generator

--

50 Ohm50 OhmCoaxCoaxUSBUSB

ConnectorConnector Nearest Nearest Device Device

Under Test Under Test

Test Supply VoltageTest Supply Voltage

15.8 Ohms15.8 Ohms

143143OhmsOhms

143143OhmsOhms

50 Ohm50 OhmCoaxCoax

May 16, 2000 16

Example: TestingTransmit WaveformsExample: TestingTransmit Waveforms

1.1. Attach DUT to USB 2.0 host controllerAttach DUT to USB 2.0 host controller

2.2. Reset the device and then issue request to place Reset the device and then issue request to place device in Test_Packet modedevice in Test_Packet mode

3.3. Unplug cable from device and replace it withUnplug cable from device and replace it withhigh-frequency test cable/fixturehigh-frequency test cable/fixture

4.4. Measure rise/fall timeMeasure rise/fall time

5.5. Capture single, complete occurrence of testCapture single, complete occurrence of testpacket on a transient capture instrumentpacket on a transient capture instrument

6.6. Perform eye pattern analysis on waveform recordPerform eye pattern analysis on waveform record

May 16, 2000 17

Example: Testing Receiver Sensitivity and Squelch ThresholdExample: Testing Receiver Sensitivity and Squelch Threshold

1.1. Attach DUT to USB 2.0 host controllerAttach DUT to USB 2.0 host controller2.2. Reset the device and then issue request to placeReset the device and then issue request to place

device in Test_SE0_NAK modedevice in Test_SE0_NAK mode3.3. Unplug cable from device and replace it with test Unplug cable from device and replace it with test

cable/fixturecable/fixture4.4. Using data generator, apply IN token packet while Using data generator, apply IN token packet while

varying amplitude, frequency, and injected jittervarying amplitude, frequency, and injected jitter5.5. Using a differential high-impedance probe, monitor Using a differential high-impedance probe, monitor

the cable to see under which conditions device the cable to see under which conditions device responds with NAK handshakeresponds with NAK handshake