Hi I'm not bashing the Arm parts, they are nice gizmos. They don't do the clock chains the way they do because they are lazy. They very much plan things out. Their main target audience is low power portable gear. Having a part that drops down to very low current when nothing much is going on is one of their goals. That drives them to keep the clocks / VCO's as slow as they possibly can. They worry about every uA of current drain…
Bob On Jan 1, 2013, at 1:14 PM, Attila Kinali <att...@kinali.ch> wrote: > Hoi Bob, > > On Tue, 1 Jan 2013 12:03:49 -0500 > Bob Camp <li...@rtty.us> wrote: > > >> On Jan 1, 2013, at 11:34 AM, Attila Kinali <att...@kinali.ch> wrote: >> >>> What about those uC that use a VCO that runs up at several 100MHz (i've >>> seen up to 800MHz) and devide it down to what they actually need. >>> Shouldnt this improve jitter quite considerably? > >> Most of the small micro's don't get very fancy on the clock chain. >> You are lucky if the VCO is running at twice the CPU clock. In some >> cases the input capture(s) (and PWM's) are running directly on the >> VCO (at say 72 MHz) and the CPU is running at half or a quarter of that. > > That's why i was specifically asking about those uC which use a higher > frequency VCO for their clock generation. Ie not the tiny 8bit stuff, > but those in the ARM7/Cortex-M3 class. > > Attila Kinali > > -- > There is no secret ingredient > -- Po, Kung Fu Panda > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
