> I have a clock with CMOS output running around a pc board, roughly 8
> inches, to the XTAL input of a PIC. The clock is 16 Mhz, and while scoping
> it, I see that it rings badly, i.e. large overshoot on the rising edge and
> large undershoot on the falling edge. Spectrum analyzer picks it right up!
> Nice 16 Mhz picket fence.
>
> How may I clean up this ringing?

Damp it out with a series R at the source end. It can be quite high
as you are going into the Xtal input and don't have to worry about
logic level rise and fall times. That means that the capacitance of
the line is of more concern to you than the characteristic impedance
and matching it.

It is probably of no consequence as there is no harm in putting the R
in anyway, but did you calibrate your scope probe and eliminate the
probe ground lead as a source of your signal ?

Regards,

Steve.

======================================================
Steve Baldwin                Electronic Product Design
TLA Microsystems Ltd         Microcontroller Specialists
PO Box 15-680, New Lynn      http://www.tla.co.nz
Auckland, New Zealand        ph  +64 9 820-2221
email: steveb@tla.co.nz      fax +64 9 820-1929
======================================================

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics