[Milkymist-devel] Video input crystal selection
sebastien at milkymist.org
Thu Mar 10 15:27:59 PST 2011
Reminder from the ADV7181 datasheet:
"This is the input pin for the 28.6363 MHz crystal, or can be overdriven
by an external 3.3 V, 27 MHz clock oscillator source. In crystal mode,
_the crystal must be a fundamental crystal_."
The crystal that I initially selected (CITIZEN AMERICA CSA309) is a
fundamental crystal. The Yoketan units you have should probably be as
well (the datasheet says "nominal frequency"), but if it's in fact an
overtone crystal, this might explain the problems we had...
I just checked this after I noticed that the amplitude of the
oscillations with my crystal (CSA309) is some 2x bigger than with your
crystal (Yoketan). That being said, I measured the oscillation with the
CSA309 only on my board with the non-working video input, so it could
simply be linked to that problem instead.
In either case, check that before selecting a new crystal for RC3.
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