Larry- Thanks for your help...I appreciate the input. I suppose I would have known about the 18F series, had I looked in the manual a bit. Olin- I found your input to be somewhat impolite, as my messages are in plain text with no formatting. If you are seeing it not monotype fonts for your ASCII art, it is because of the set-up in your mail client, not because everyone else in the world is doing it wrong. Mike Hord >From: Larry Bradley >Reply-To: pic microcontroller discussion list >To: PICLIST@MITVMA.MIT.EDU >Subject: Re: [PIC]: Oscillator Options for 18F45x and 16c7x5 >Date: Thu, 24 Apr 2003 12:28:26 -0400 > >The Digikey xtals are fine - order them for parallel use - these will have >a capacitance displayed in the spec. The accuracy is typically 25 to 30 >ppm. > >The 18 series use 10 mHz xtals and a builtin PLL to go to 40 mHz, they >don't use a 40 mhz xtal. > >You should be able to just swap the xtals. I use 18 pf caps. > >If you use a SERIES xtal in this circuit, you will find that the frequency >is high - I have two 20 mHz series xtals that run about 140 ppm high in >frequency. > >Don't forget to change the oscillator setup from XT to HS when you go to >the higher frequency xtals. > >Larry > >At 11:20 AM 4/24/2003 -0500, you wrote: >>Up until now, I've really only played around with a 16F87x using a 4-MHz >>crystal and 2 22 pF ceramic disc caps... >> >>Osc1 Osc2 >>| | Please excuse the >>| | crudeness of this >>|---|0|---| diagram, but I >>| | don't have time >>=== 22pF === to make it to >>| | scale... >>| | >>|_________| >> | >> Gnd >> >>I buy el cheapo XTAL's from Digikey, 4 MHz 20 pF Cload. I'd like to go to >>20 MHz crystals for some 16F87x projects, and the 16C7x5 USB jobs need a 6 >>or 24 MHz, and the 18F45x can handle up to a 40 MHz. Can I basically just >>swap out the 4 MHz with the other part, even if the other part is a Series >>capacitance crystal? Or do I need to modify it somehow? Accuracy is >>important to me, but not critical...100 ppm or so is acceptable. Thanks! >> >>Mike Hord >> >> >>_________________________________________________________________ >>STOP MORE SPAM with the new MSN 8 and get 2 months FREE* >>http://join.msn.com/?page=features/junkmail >> >>-- >>http://www.piclist.com hint: The PICList is archived three different >>ways. See http://www.piclist.com/#archives for details. > >Larry Bradley >Orleans (Ottawa), Ontario, CANADA > >-- >http://www.piclist.com hint: The PICList is archived three different >ways. See http://www.piclist.com/#archives for details. _________________________________________________________________ MSN 8 helps eliminate e-mail viruses. Get 2 months FREE*. http://join.msn.com/?page=features/virus -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.