Hello everyone, -----Original Message----- From: Aaron J. Grier [mailto:aaron@...] Sent: Thursday, May 23, 2002 12:43 PM To: 68300@yahoogroups.com Subject: [68300] Re: Favorite clock frequency? On Wed, May 22, 2002 at 10:46:57PM -0500, Scott Newell wrote: > Just going through some old notes, and I noticed that at one time I > calculated 22.118400 MHz as a nice number: it allows you to run the > UARTs (SCI and TPU) at all the standard baud rates with no error. > Using the PLL, it can be generated 38.400 kHz rock. 38.4 kHz also > gives you a even 100 Hz PIT rate, something 32.768 kHz can't. [Melear Charles-rdph40] Well, actually, the spec for a 25 MHz part is 25.7 MHz so you are not overclocking by much. I think you can take a chance on 0.1 MHz. the next sweet point for baud rates after 22.118400 is 25.80480, which is slightly above spec for the 25MHz part, isn't it? with 32.768kHz you hit a similar spot at 22.020096, which gives < 1% for all standard baud rates. charles, what's the word on slightly overclocking these processors to hit the sweet spots? > So why does everyone seem to use 32.768 kHz? Availability? [Melear Charles-rdph40] The 32.768 KHz crystal is widely used in watches. It is extremely common. It is also a power of 2. it's the one listed in the motorola literature, so it gets used by default. :) -- Aaron J. Grier | Frye Electronics, Tigard, OR | aaron@... Yahoo! Groups Sponsor ADVERTISEMENT <http://rd.yahoo.com/M=226020.2067224.3532861.1971030/D=egroupweb/S=1706554205:HM/A=1073422/R=0/*http://www.qksrv.net/click-1084497-610300?url=http://www.tv/en/landing.shtml&HHcode=yhc3my2> <http://us.adserver.yahoo.com/l?M=226020.2067224.3532861.1971030/D=egroupmail/S=1706554205:HM/A=1073422/rand=548826757> --------------------------------------------------- To unsubscribe from this group, send an email to: 68300-unsubscribe@yahoogroups.com To learn more about Motorola Microcontrollers, please visit http://www.motorola.com/mcu <http://www.motorola.com/mcu> Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service <http://docs.yahoo.com/info/terms/> .
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RE: [68300] Re: Favorite clock frequency?
2002-05-23 by Melear Charles-rdph40