Hi Mark I did (read the data sheet) it looks like it will work fine to run the HSPLL to me. I agree I don't need to go that fast so that is why I thought from the beginning that my trusty 4.096 MHz part will do just fine. Down the road is another story for another day. Thanks for the post/help. Phillip Things should be as simple as possible but no simpler Phillip Coiner CTO, GPS Source, Inc. Your source for quality GNSS Networking Solutions and Design Services, Now! -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of Mark Rages Sent: Thursday, June 29, 2006 11:51 AM To: Microcontroller discussion list - Public. Subject: Re: [PIC] C18 calculating the interrupt loading On 6/29/06, Phillip wrote: > Hi Jan-Erick > > Crystal: > I did not realize the HSPLL PLL mode could be made to work like that but it > is great to know. > So I'm sure you know what my next question is....Can I run the HSPLL with my > trusty crusty 4.096MHz crystal for 16MHz internal eh? > Yes. Read the datasheet. But you sure don't need 16MHz for what you are trying to do! You have listed: 1) 9600 baud serial communication 2) Nine A/D readings/second 3) Debouncing keypresses You do not need two levels of interrupt for this. By way of example, my last application had: 1) 115200 baud serial communication 2) One hundred A/D readings per second 3) Two floating-point PID loops 4) Edge triggered PLL 5) I2C communications to a DAC This used a 16F688, a much lower-spec chip than the one you are using. It has one level of interrupts. It was running at 8 MHz. And this was *not* some feat of engineering to shoehorn everything in. My point: You have *lots* of resources available. No need to complicate things. Read the datasheet. Regards, Mark markrages@gmail -- You think that it is a secret, but it never has been one. - fortune cookie -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist