Technical data

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.