Teledyne LeCroy USBTracer_Trainer - Users Manual - Manual (Page 258)

Chapter 10: Recording Options USB Protocol Suite User Manual
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LeCroy Corporation
Note 2: On Voyager M3i only, there is an option to use the Internal 10-Mbps clock as a
clock source. The Voyager 5-MHz clock is on both the Clock-A-Out and Clock-B-Out
connectors. However, LeCroy does not recommend using the Voyager clock. Voyager
clock input is AC coupled and has no requirement for common mode voltage.
• For Host emulation, connect Clock Out A to Clock In A. You can use Clock Out B as
the clock source for the DUT.
• For Device emulation, connect Clock Out B to Clock In B. You can use Clock Out A
as the clock source for the DUT.
IMPORTANT: If you switch from Very Slow Clock back to Gigabit data rates, you must
save the recording options and then power-cycle the Voyager.
External Clock Input Specifications
The external clock input is 3.3 volt LVPECL and operates on the USB 3.0 differential
signals only (not USB 2.0 signals). Device setup should be AC coupled at the clock input
with a 10 uF ceramic capacitor.
When enabled, the external slow clock option affects both the SuperSpeed analyzer
(record) and the exerciser (transmit) frequencies. The clock source must be able to drive
a 50 ohm load with a minimum peak-to-peak voltage swing of 200 mV. Maximum
peak-to-peak voltage swing should not exceed 1700 mV. Note that these voltages are
single ended, as only one of the differential signals is connected via the coaxial cable.
When operating at 1.25 Gbps to 5 Gbps modes, the data lines are directly connected to
Rocket I/O ports. The very slow external clock mode will bypass the high speed
Rocket I/O logic and use a SERDES implemented in the FPGA fabric. The low end of
clock speed is limited by the value of the AC coupling caps on the inputs and the trace
impedance. The SMA inputs use a 0.1 uf capacitor with a nominal trace impedance of
50 ohms. This mandates the 350 kHz slow clock limit over the Voyager SMA inputs.
Some software-based emulation environments require rates as low as 10 Hz. For this
application, LeCroy offers a one-time customization of the Voyager hardware platform by
removing the 0.1 uf capacitor on the Voyager SMA inputs, allowing the clock inputs to
track externally supplied clock frequencies below 350 kHz. Although removal of this
capacitor will render the SMA input ports non-compliant with 5 Gbps signaling, the native
USB 3.0 connectors will continue to operate within the USB 3.0 electrical specification.