Dear neoflash,

> if I use dual-modulous divider as shown in the figure, what is the safe time
> window to update the divider ratio control word P<N:0?
>
> Intuitively the safe window is to update the p<n:0> when all mod0-modn signals
> are logic low. Not sure if this is correct and can assure the divider operates
> glitch-free.

An approach I have used is to synchronize the divider option. p(N:0>, to the output clock. There will still exist a maximum input frequency, but this approach worked well for me.

Shawn