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4
Setting the Capture Options
Figure 2
Field
Capture Memory Depth
Capture Link Speed
34
Capture Setup
Description
Lets you select the trace memory depth. Deeper traces capture more activity but take longer to save and process.
At times, in a bidirectional setup, the memory for one of the directions is filled up much earlier than the memory for
the other direction, for instance, when one of the directions starts sending training sequences even before the other
direction starts or when one direction sends large data packets as compared to smaller packets from the other
direction. This results in data capture for one of the directions to stop while the other direction's data capture is still
running. In such a situation, you would see data of only one of the directions in the trace after the memory is full for
the other direction.
For such a situation, you should consider:
•
increasing the memory depth for the direction to get data for both the directions.
•
setting the trigger condition such that both directions are transmitting data when data capture starts.
•
enabling bidirectional trimming (explained below) to remove extra non-overlapped packets for the two
directions.
Lets you specify the link speed of the data to be captured:
•
Gen 1 — select this when capturing data on 2.5 Gbps links.
•
Gen 2 — select this when capturing data on 5 Gbps links.
•
Gen 3 — select this when capturing data on 8 Gbps links.
•
Auto – select this option when testing link speed switching scenarios. On selecting this option, analyzer
automatically detects the link speed change and accordingly starts capturing data based on the changed link
speed. The Auto option also has a drop-down listbox displayed with it. From this listbox, you can select either
Gen1 or Gen2. If you select Gen1 from this listbox, then analyzer prioritizes and captures the Gen 1 ordered
sets while switching speed from Gen 3. If you select Gen2 from this listbox, then analyzer prioritizes and
captures the Gen 2 ordered sets while switching speed from Gen 3.
Based on the selected link speed, the speed LED of the Analyzer pod on which the logical Lane 0 is present will glow.
The following color coding is used to interpret the status of the speed LED.
•
Off - This means that the system is not configured.
•
Red - This means that the link speed is not detected or not configured.
•
Yellow - This means that the link speed is 2.5 Gb/s.
•
Green - This means that the link speed is 5 Gb/s.
•
Blue - This means that the link speed is 8 Gb/s.
If you selected a fixed speed (Gen1, Gen2, or Gen3), then the speed LED will glow according to the selected speed. If
you selected the Auto speed option, then the speed LED will glow according to the detected speed.
NOTE: If you want to set the Capture Link Speed to Gen1, Gen2, or Gen3, then you must ensure that Lane Reversal is
not set to Auto in the Connection Setup tab.
Keysight U4301 PCIe Gen3 Analyzer User's Guide
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