Teledyne LeCroy Inspector - Users Manual - Manual (Page 28)

CATC CATC Inspector User’s Manual Version 2.31
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4.4.1.2 Idle State Recording Selection
“Idle” is a valid state of the USB physical layer between packets. By default, the CATC Inspector
analyzer records all bus activity, including the Idle state; in this mode, the available buffer space
permits the recording of just under 0.67 second of full-speed (5.36s of low-speed) traffic.
Idle state recording can be disabled by selecting the “Don’t Record” option (in the Idle State
panel of the Data Recording Options dialog box, shown above); this will increase the recording
time to just under 4 minutes of full-speed traffic (low-speed recording time is traffic-dependent,
and could be hours). In this mode the analyzer suspends recording upon detection of the Idle, and
resumes upon detection of the start of the next packet (SOP), which is a transition from the J to
the K state.
Although this permits greatly increased recording times, there are two associated drawbacks:
1. When bus traffic is at a minimum, it can take a long time to fill the analyzer’s recording
memory. This is especially true if event detection mode is selected (and thus the memory size
cannot be reduced below one megabyte). Once a triggering event has been detected it may
still take several minutes before recording stops, due to limited bus traffic filling the memory.
Two things can be done to help alleviate this problem: setting the amount of post trigger
memory to a minimum, and stopping manually once the trigger has been detected. The
analyzer provides both LED and on-screen “triggered” indicators for this purpose.
2. Recording without Idle state eliminates the real-time information, so the CATC Inspector
software will not be able to support any of the timing related features.
4.4.1.2.1 User Input Data Recording
Whenever the Idle state is being recorded, it is also possible to simultaneously record up to four
externally supplied User Input Data signals (from the External Interface Breakout Board) along
with USB traffic. To select this option, mark the “Save User Input Data” checkbox in the Idle
State panel.
This can be quite useful for recording state or timing information from external devices, or for
extending the event detection capability of the analyzer. For example, it is possible to “jumper”
output signals from the breakout board back to the user data inputs, in order that selected events
can be viewed in the display while not selected as triggers. External timing signals (which should
be TTL levels to be recorded properly) are sampled once for each byte of USB traffic.
Recording, saving (in USB data files), and displaying this external timing and state data adds
notably to the processing time of the Inspector software (and the size of the traffic files); thus it is
recommended that this only be enabled as required.