Technical data

132 4000 X-Series Oscilloscopes Advanced Training Guide
4 Serial Bus Decoding & Triggering, Search & Navigation, and Segmented Acquisition Labs
Lab #22: Decoding, Triggering, and Searching on Universal Serial Bus
(USB) Signals
In this lab you will learn how to set up the scope to decode and trigger on
USB traffic. In addition, you will learn how to use the scope's automatic
Search & Navigation capability, as well as use Segmented Memory
acquisition to capture multiple and consecutive occurrences of a particular
operation. This lab does not provide a tutorial on the USB protocol. Also,
the USB signal provided is not a complex representation of true USB
traffic; our training signal will consist of four IN transactions, using
low- speed (USB 1.1) for simplicity. To complete this lab, your scope must
be licensed with the USB 2.0 Full/Low Speed serial decode and triggering
option (Option USF). You can verify the installed options on your
oscilloscope at [Help] > About Oscilloscope.
1 Connect the channel-1 probe to the Demo 1 terminal and ground.
2 Connect the channel-2 probe to the Demo 2 terminal and ground.
3 Press [Default Setup] on the scope's front panel.
4 Press [Help]; then tap the Training Signals softkey.
5 Select and enable the USB signal.
6 Set channel- 1 to 1.00 V/div.
7 Tap the channel 2 button to enable channel 2 output.
8 Set channel- 2 to 1.00 V/div.
9 Set channel- 2 offset to 3.50 V.
10 Push the trigger level knob to set the trigger level to approximately 50%.
11 Set the scope's timebase to 20.0 µs/div.
You should see on your scope's display what appears to be an un- triggered
display of two digital signals similar to Figure 89. Your scope is actually
triggering on random rising edges of channel- 1, which is the scope's
default trigger condition. But these signals are too complex to establish a
unique trigger point using simple edge triggering. Let's first set up the
scope to intelligently decode this data stream based on the USB protocol,
and then we will establish a more unique trigger point using USB
triggering.