Note: Nothing in this email is to be construed as a recommendation on the part of the author to operate any integrated circuit outside its vendor-specified parameters ;-) Very, very early in the PIC18 days I built up a project using a PIC18C252 that was very timing dependent. I was rather irritated that all my timing seemed to be off by about 10% (fast). After a lot of head scratching, probing and puzzling I finally noticed that the 10MHz crystal sold to me by Digikey was really something like 11.09MHz (it said so on the crystal, but the bag it came in said 10MHz). Except for the timing issues, the chip did seem to work perfectly, at least at room temperature with a 5V nominal power supply. Bob Ammerman RAm Systems ----- Original Message ----- From: "Electron" To: "Microcontroller discussion list - Public." Sent: Tuesday, May 17, 2005 12:31 PM Subject: RE: [PIC]: PIC18F at 44.5MHz. Anybody has experiences to share? > > At what voltage were you running it? :) > > > At 11.09 2005.05.17 -0400, you wrote: >>Hmmm... I have a prototype 18F6585 based device on my desk. Just for grins >>I >>tried changing the 10MHz xtal to 16MHz (Bumps clock from 40MHz to 64MHz) - >>it didn't work for me :-( If I can find an 11MHz xtal lying around I'll >>try >>it at 44MHz. >> >>-- Mark >> >>> -----Original Message----- >>> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu]On Behalf >>> Of Jinx >>> Sent: Tuesday, May 17, 2005 9:27 AM >>> To: Microcontroller discussion list - Public. >>> Subject: Re: [PIC]: PIC18F at 44.5MHz. Anybody has experiences to share? >>> >>> >>> > > Does anybody have experiences to share about overclocking >>> > > 40MHz-rated PIC18F parts to about 44.5MHz? >>> >>> Some time last year I posted about an 18F452 that I accidentally >>> connected an 18.432MHz xtal to and then turned the PLL on. It >>> did appear to run OK with some very simple timing tests at >>> 73.728MHz but I would never expect to try that in production >>> nd without a complete battery of tests on all the modules it's >>> impossible to say whether it was a fully functional device at that >>> speed >>> >>> Although you've been advised that 44.5MHz is out of spec, that >>> doesn't necessarily mean it won't work reliably. Just that if it >>> doesn't you've no one to blame but yourself. I don't know what >>> Microchip's actual criteria are for specifications at the higher >>> frequencies, but at the bottom end you probably can overclock >>> parts. For example, a -04 part is guaranteed to run at 4MHz, >>> but came from the same batch as -10 parts, and failed the 10MHz >>> test. So it could run alright at 6MHz or 8MHz >>> >>> It might very well be the case that some 40MHz parts will run >>> at 44.5MHz. You would have to sort out which ones will, and >>> with the functions you're using >>> >>> >>> -- >>> 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 > -- > 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