Lpc2000

Interesting. You are probably aware of this, but there is an IEEE
standard for this. Its IEEE 1588 and is used as part of the LXI
instrumentation standard. See this link for more information.

http://www.lxistandard.org/papers/paperOverview/White_Paper_1_The_Appliaction_of_IEEE_1588_to_Test_and_Measurement_Systems.pdf

I believe that the same concepts are used in the CAN derived TTP.

    Andy..

--- In lpc2000@yahoogroups.com, "Andy" <me@...> wrote:
>
> I am investigating exactly that point (academic project), seeing how
acurate 
> a shared clock network I can produce over ethernet.  I have created
a custom 
> protocol for ethernet, using the W3100A in mac layer raw mode. 
Controlling 
> the traffic seems to produce a fairly low jitter network.  Thanks
for the 
> pointer to your app note, should be very helpful.
> 
> Andy.
> 
> ----- Original Message ----- 
> From: "Robert Adsett" <subscriptions@...>
> To: <lpc2000@yahoogroups.com>
> Sent: Friday, May 12, 2006 5:21 AM
> Subject: Re: [lpc2000] Interrupt function declaration
> 
> 
> At 09:27 AM 5/11/06 +0100, Andy wrote:
> >Robert,
> >I am running a shared clock network over ethernet, so to reduce
task jitter
> >on the slave nodes the timer0 interrupt needs to be as close as
possible.
> 
> Do you need to have your message sent as close to 1mS as possible? 
If so
> I'm surprised that ethernet uncertainties don't swamp any jitter
from the
> interrupt.  Never mind the additional uncertainties introduced by
whatever
> higher level protocol you are running on ethernet (probably TCP/IP
consider
> you are using WIZnet?)
> 
> Or do you just need to know the time that you sent the packet as
accurately
> as possible.  If that's the case (and I think it should be with a good
> clock synchronization algorithm) then there are other approaches
that will
> give you greater accuracy without the interrupt overhead. With the
timers
> on the LPC series it is quite easy to setup a polled timer that will
give
> you time with an precision of a few tenth's of a uS that will not
exhibit
> any significant wrap around oddities as long as you poll it every few
> minutes.  Accuracy is actually limited in most cases by the crystal.
Chalk
> one up for 32bit timers, one of the features I really like on this
micro.
> 
> See
> 
>
http://www.aeolusdevelopment.com/AppNotes/LPC210X/an-timerperformance.pdf
> 
> It's an app note I did on taking some performance measurements on
such a 
> clock.
> 
> 
> Robert
> 
> " 'Freedom' has no meaning of itself.  There are always
restrictions,   be
> they legal, genetic, or physical.  If you don't believe me, try to
chew a
> radio signal. "  -- Kelvin Throop, III
> http://www.aeolusdevelopment.com/
> 
> 
> 
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