On Thu, 26 Mar 1998, Dennis Ferguson wrote:

> > >I think what you want is to just take a timestamp in the interrupt
> > >routine at character reception time, and then have the line discipline
> > >use that timestamp rather than taking its own in the soft interrupt
> > >handler.
> > 
> > Uh, but *which* char should it be timestamping? (All of them?)
> > 
> > Ken Hornstein says the gadget box doesnt give a PPS signal from CHU.
> 
> All of them.  CHU sends a ten or twelve byte string using standard
> 300 bps modem tones, 10 times per minute.  Each byte is transmitted
> at a precise, well-known time with respect to the on-time second, so
> the arrival of each byte represents a time-of-day sample, the collection
> of which the xntp driver filters into an offset estimate applied every
> minute.

I see two problems with this idea:

1) the character receive routine has no idea what line discipline is in.
So should it timestamp all characters all the time?

2) Some ports, like mac68k, don't have nanosecond (or microsecond or
millisecond) resolution clocks with which to time stamp things. What then?

Take care,

Bill