Hi The little Arm7/ Cortex-M3 micro's don't pay as much attention to the clock chain as some of their bigger brothers (like a Sandy Bridge I7) do. At least the M3's and M4's I have seen are running the VCO at 50 to 150 MHz to generate a CPU clock at that frequency. The clock is divided by two for the RAM clock, and divided by two again for the flash clock. They may be doing a fake out on the VCO frequency. If they are, it's well hidden.
Bob On Jan 1, 2013, at 1:14 PM, Attila Kinali <[email protected]> wrote: > Hoi Bob, > > On Tue, 1 Jan 2013 12:03:49 -0500 > Bob Camp <[email protected]> wrote: > > >> On Jan 1, 2013, at 11:34 AM, Attila Kinali <[email protected]> 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 -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
