Re: Kernel PLL, microkernel and the simulator.
- From: blu <brian.utterback@xxxxxxxxx>
- Date: Tue, 22 Jul 2008 18:43:37 -0700 (PDT)
On Jul 21, 10:35 pm, "David L. Mills" <mi...@xxxxxxxx> wrote:
Brian,
The data actually used to update the clock can be as old as seven poll
periods old. This is the result of the clock filter and is expected.
However, the dynamics of the clock discipline, in particular the time
constant, are designed for this condition. Theory requires that the
sampling rate of the feedback loop be at least the Nyquist rate, which
is twice the bandwidth (inverse time constant) of the loop filter. In
particular, the sampling rate of the NTP loop, even using only every
seventh sample, is twice the Nyquist rate.
Dave
Okay, so how is the bandwidth equal to the inverse TC, and is that the
TC as in 3 or as in 2^3=7? I don't understand the meaning of the term
bandwidth in this context. And when you say that it works even if you
only use every seventh sample, is that even if the sample is seven
poll intervals old every time?
Brian Utterback
brian dot utterback at sun dot com
.
- Follow-Ups:
- Re: Kernel PLL, microkernel and the simulator.
- From: David Woolley
- Re: Kernel PLL, microkernel and the simulator.
- References:
- Kernel PLL, microkernel and the simulator.
- From: brian . utterback
- Re: Kernel PLL, microkernel and the simulator.
- From: David L. Mills
- Kernel PLL, microkernel and the simulator.
- Prev by Date: Re: Linux 11-minute mode (RTC update)
- Next by Date: Re: NTP Events
- Previous by thread: Re: Kernel PLL, microkernel and the simulator.
- Next by thread: Re: Kernel PLL, microkernel and the simulator.
- Index(es):
Relevant Pages
|
