Agilent Technologies N5416A Manual de Serviço descarregar pdf (Página 206)

206 Notes on USB Electrical Compliance Testing

7 Low and Full Speed Tests

Configuring the Tests Make sure you set the Test Type configuration option

to “Low- Speed Near End” before running the test.

Connecting the Equipment The USB automated test application will prompt

you to perform these connection steps:

1 For 54831B/D and 54832B/D oscilloscopes, use 1165A passive probes.

For the 5485XA, 80000 and 90000A Series oscilloscpes, use E2697A

high- impedance converter with 10:1 passive probes, or 1156A active

probes.

2 Attach the passive probes to the oscilloscope's Channel 3 and Channel 2

inputs.

3 Attach the SQiDD board to the hub under test.

4 Attach the upstream port of the hub under test to the end of 4

self- powered hubs and a host system. Hub #1 has to be a full speed

hub. The other hubs can be either full speed or hi- speed hubs.

5 Attach a low speed device to the same section of the SQiDD board. If

the section has a switch, it should be set to ON.

6 Connect the oscilloscope Channel 2 probe to D- probe point of the

device under test portion. Connect the oscilloscope Channel 3 probe to

the D+ probe point of the device under test portion.

7 Exit the HS Electrical Test Tool if you have previously launched it.

NOTE

The best method to capture and analyze low-speed downstream signal quality is to capture

both a keep-alive (low speed EOP) if present and a SOF packet. Hubs are required to

generate keep-alives when there is full speed traffic and pass them on to low speed

devices.

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Agilent Technologies N5416A Manual de Serviço Página 206