External Clock set to 64MHz on USRP2/N210

GNU Radio
1

Hello All,

There was a previous project done in my research group where a external
device generates a 64 MHz clock to the USRP1 in addition to a PPS
signal. Currently I am making appropriate changes so a similar project
can be used for the USRP2/N210. I was wondering if the same 64MHz
external clock is connected to the USRP2, would this override the
default 100MHz master clock? I am still fairly new to the USRP, so this
could be a very trivial question. My understanding right now is that an
external reference clock has to be equal to an integer division of
100MHz (i.e 100MHz/n), but this could be totally wrong. Any advice on
this issue would be greatly appreciated.

Thank you very much,
Rob

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2

On Wed, Feb 15, 2012 at 7:06 PM, rmsrms1987 [email protected]
wrote:

external reference clock has to be equal to an integer division of
100MHz (i.e 100MHz/n), but this could be totally wrong. Any advice on
this issue would be greatly appreciated.

USRP2 and N210 were designed to take a 10MHz reference clock, the type
commonly generated by reference oscillators and GPSDOs. It is possible
to
use a different frequency which is divisible into 100MHz, but you will
have
to modify uhd/host/lib/usrp/usrp2/clock_ctrl.cpp to cope with a
different
reference frequency. There is no easy path to getting a 64MHz external
reference into the USRP2/N210.

–n