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3. Pass a “POSSIBLE BAD EOP” status to the
Analyzer.
A status of “POSSIBLE BAD EOP” should be treated
as cautionary and the user would be advised to view
the received signals in timing mode by doing the
following.
1. Attach POD 3 of the analyzer to POD 3 of the USB
Analysis Probe.
2. Attach a flying lead set to stake pins RCV, VP and
VM.
3. In state mode trigger on PID “ POSSIBLE BAD
EOP”. Using the arming control trigger the timing
Analyzer from the State Analyzer.
4. Once the State Analyzer Triggers switch to Timing
Analyzer Waveform 2.
Low Speed/High
Speed detection
The USB Analysis Probe can switch automatically
from high speed to low speed upon the detection of
the Preamble PID. The Analysis Probe then detects
only low speed traffic. Upon the receipt of a low
speed acknowledge or an internal time-out (greater
than 16 low speed bit times). The Analysis Probe will
switch back to high speed. The following explains in
more detail the sequences the Analysis Probe looks
for in making the decision whether to switch from high
speed to low speed and back.
Sequence 1
1. Detection of a PREAMBLE - switch to low speed
2. Look for SETUP or OUT packet in low speed then
switch back to high speed.
3. Look for PREAMBLE - upon detection switch to
low speed.
4. Look for a single DATA packet or handshake or
time-out.
5. On receipt of a DATA packet look for a handshake
or time-out .
6. On receipt of a handshake or the occurrence of a
time-out the pre-processor switches back to high
speed.
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