> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On
Behalf
> Of Michael Watterson
> Sent: 19 May 2011 09:34
> To: Microcontroller discussion list - Public.
> Subject: Re: [PIC] Using PC18F2455 for RS232
>=20
> On 19/05/2011 09:19, IVP wrote:
> > The range is better than it used to be. For example Murata have
> > several tight products. Not quite crystals but in the 100's ppm
> > (0.05% typical)
> >
> > http://www.murata.com/articles/ta0541.pdf
> >
> > Meeting the demand for USB etc
> >
> > Factors for the OP to consider include cost (and cost benefit),
size,
> > assembly, long-term (vs initial accuracy), stability and
availability
>=20
> OK that's good.
>=20
> But if you are doing less than 10,000 to 100,000 boards the cost
saving
> of Resonator is hardly worth it. Miniature crystals, even in SM form
> factor are pretty cheap. Either way the only issue compared to
internal
> oscillator is using 2 pins.

Resonators have some significant advantages over crystals besides cost;
they are physically more robust than crystals, start up faster and are
less sensitive to drive levels.

It's not difficult to get resonators that are stable enough for
asynchronous comms; a quick trawl of Farnell shows they don't sell
anything worse that +-0.5%.

Mike

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