On Wed, 12 Sep 2012 00:42:48 +0200, "Peter Krengel" <[email protected]> wrote:
>I'm looking for a possibility to make an automatic switching >between the internal µC oscillator (Atmel µC) to the 10MHz output >of my thunderbolt to use it as a precise µC clock. Has anybody an idea how >to do best without disturbing the accuracy of the ref. signal? Which Atmel microcontroller? Is this an application where you are modifying an existing design and only have access to the clock signal? Many microcontrollers support selecting from multiple clock sources and include the logic necessary to do so without glitching. They do not usually have more than one high speed clock input though. One way to get around that is to switch from the high speed external clock to an internal clock or a low speed external clock, swap the high speed clock source, and then switch back. There are limits on the minimum positive and negative pulse widths in the clock so any transition needs to be glitch free. A little bit of external logic can handle that or a VCO and PLL like Chris suggests. http://www.eetimes.com/electronics-news/4138692/Techniques-to-make-clock-switching-glitch-free _______________________________________________ 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.
