[time-nuts] More on SiLabs 5340

[Chris Caudle]

On Mon, January 29, 2018 2:38 pm, John Ackermann N8UR wrote:
> to do, though, was feed 10 MHz into the "Input 0" port which apparently
> disciplines the free-running crystal.

It doesn't discipline the crystal oscillator, the crystal oscillator is
multiplied up and used as the clock to run a DDS block.  The 10MHz signal
you input is the reference input to a digital PLL, and the output of the
PLL modifies the tuning word of the DDS.

In free run mode it works similarly, but the tuning word never changes,
the DDS control value is chosen based on assuming that the DDS clock is
running exactly at nominal frequency.

-- 
Chris Caudle