On Wed, May 14, 2003 at 09:21:12AM -0400, Olin Lathrop wrote: > > Just guessing, but it may be because the external oscillator needs to > provide a relatively strong drive. That makes sense, though I would have expected that to be covered in the "max" current rating rather than the "typical". > Why would you want to use an external crystal oscillator anyway when the > PIC has a perfectly good crystal driver built in? The board will have a PIC and a CPLD on it. The CPLD cannot generate its own clock, and is capable of higher clocks than the PIC. While I could leech off of the OSC2 pin of the PIC, even the PIC can't use crystals >25Mhz. The only way to get 40Mhz would be an 18F452 with PLL, and then the CPLD would only see 10Mhz. Also, by freeing up OSC2/CLKOUT I can connect that to one of the other global clock inputs on the CPLD, to have the instruction clock available within the CPLD, or optionally on the 18F452 drive it directly as RA6. I'm not sure what it will do on an 16F877. Anyway, it's a proto board, so a socketed (half size) oscillator seems like a good way to go. Power isn't critical, I just spotted the ratings while placing my digikey order and wondered what was going on inside that used all that current. -- Ben Jackson http://www.ben.com/ -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.