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→Turning off USB Clock & Triggering the FPGA
You can disable the USB interface clock (i.e., the clock used by Address/Data lines). Generally this is recommended during the power measurement, as a separate clock is provided for clocking the cryptographic module. The clock can be turned off with:
<syntaxhighlight lang="python">cw.usb_clk_setenabled(False)
</syntaxhighlight>
A complete example of a power measurement might look like this:
<syntaxhighlight lang="python">#arm scope here
cw.usb_clk_setenabled(False)
cw.usb_trigger_toggle()
</syntaxhighlight>
You may wish to add a small delay (such as ''{time.sleep(0.05)''}) after turning off the clock.
You may also need to add a delay after triggering the pin - you don't want to turn the clock back on right away, but depending on your scope module it may report the trigger event has occurred before the capture is complete.
