Keysight Technologies U4301 User Manual page 28

3 Specifying the Connection Setup
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• Internal — selects an internal clock source. You should select Internal if the data rate is in the
range of 2.5 Gbps or 5 Gbps +/-50 ppm. Note that there is no input clock in this mode.
• External 1/2/3/4 — selects an external clock source. You should select External if the device
under test uses SSC or the data rate is in the range of 2.5 Gbps +/-300 ppm (+0% / -0.5% if
using SSC). The clock rate for external mode should be between 100 MHz +/-300 ppm (+0% /
-0.5% if using SSC).
Some important points about external reference clock selection
If you plan to use an external clock source, then you must ensure that the reference clock from
the DUT is available when you:
• select External as the Clock Source in the Setup dialog and apply the selection by clicking
Apply or OK.
• or load a configuration file that specifies the use of the external clock source.
If the reference clock from the DUT is not available to Analyzer when you apply the external
clock source selection, the Analyzer's internal PLL may not be able to attain the initial lock with
the DUT's reference clock resulting in an erratic behavior. Just making the DUT's reference
clock available at this point does not establish the lock with the reference clock. In such a
situation, you can re-establish the lock with the DUT's reference clock by performing the
following steps:
i
Ensure that the reference clock of the DUT is available.
ii
Then select Internal as the Clock Source in the Setup dialog and click Apply.
iii
Finally, select External as the Clock Source in the Setup dialog and click Apply.
Once the initial lock is established, it is maintained. You need not re-establish the lock with the
reference clock on subsequent availability/unavailability of the reference clock in the event of
DUT power off/on or on any further changes to the Setup dialog except for Clock Source or Link
Type.
Select the master lane. You can select any lane as the master lane from the lanes displayed in the
Master Lane listbox. The lanes are displayed as per the selected link width. The lane that you
select as the master lane is considered the lane for capturing the ordered sets.
Keysight U4301 PCIe Gen3 Analyzer User's Guide