One thing that must be concidered is that any error that the Resonator or crystal has will also be multiplied by 4. This could effect high speed serial IO. As I dig further into this I will post my results. ----- Original Message ----- From: "Byron A Jeff" To: Sent: Sunday, August 04, 2002 3:56 PM Subject: Re: [PIC]:Has any one ever got a PIC 18F244 chip to work at 40mh= z > On Sun, Aug 04, 2002 at 06:46:50PM +0300, =D6mer Yalhi wrote: > > I have just ordered pic 18f452 and 40mhz xtals (without reading the manual). > > do you mean to tell me that I wasted my money on the xtals? > > Yup. That's what manuals are for. They won't work. > > > All I need is just a 10MHz xtal? > > Yup. > > > I don't get it... > > The part has a 4x PLL in it. So in HS/PLL mode it'll multiply the input > clock signal by 4 giving up to 40 Mhz. > > BAJ > > > > > -----Original Message----- > > From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]On > > Behalf Of Michael Simpson > > Sent: Sunday, August 04, 2002 11:13 AM > > To: PICLIST@MITVMA.MIT.EDU > > Subject: Re: [PIC]:Has any one ever got a PIC 18F244 chip to work at 40mhz > > > > > > OK I got this baby to run at 40MHZ. > > > > Once you program with HS-PLL option you must shutdown the PIC (Reset wont do > > it) This allows the PLL to start up. > > > > Some other observations. > > When using crystals and resonators with PLL option the caps don't se= em to > > make a difference. > > > > In the 18FXX2 manual fig 2.6 does not show the use of caps. Any one know > > any thing about this. > > > > ----- Original Message ----- > > From: "Michael Simpson" > > To: > > Sent: Sunday, August 04, 2002 2:11 AM > > Subject: Re: [PIC]:Has any one ever got a PIC 18F244 chip to work at 40mhz > > > > > > > The problem is the Chip does not run 4X internaly. A 10mhz crystal with > > HS > > > and PLL does not run internaly at 40MHZ. > > > > > > > > > ----- Original Message ----- > > > From: "Byron A Jeff" > > > To: > > > Sent: Saturday, August 03, 2002 6:56 PM > > > Subject: Re: [PIC]:Has any one ever got a PIC 18F244 chip to work a= t 40mhz > > > > > > > > > > On Sat, Aug 03, 2002 at 05:46:16PM -0400, Michael Simpson wrote: > > > > > The question is for the PLL option I am using a 10MHZ Resonator. IT > > > works > > > > > at 10MHZ with or with out the PLL option. > > > > > > > > > > As far as the crystals I have tried about 20 brands and types. = I > > > purchased > > > > > about 10 each a few weeks ago so I could test. At the lower > > > frequencies > > > > > they all seem to work. fine. I have a few 10mhz crystals and again > > they > > > > > work fine at XT or HS as 10MHZ. But in HS/PLL they are still running > > at > > > > > 10MHZ. > > > > > > > > (sound of head scratching...) > > > > > > > > They are supposed to run at 10 Mhz. So what exactly is the proble= m? > > > > > > > > The PLL is internal and uses the 10 Mhz external signal to genera= te the > > 40 > > > Mhz > > > > clock internally. So there should be no change in the external > > appearance > > > of > > > > the external oscialltor. > > > > > > > > It's supposed to run at 10 Mhz. > > > > > > > > So I only have one question: When you enabled the HS/PLL mode did the > > chip > > > > get 4 times faster than HS mode? > > > > > > > > Lastly did you read the errata page for the 18C chips. There are some > > > issues > > > > on oscillator speed based on whether the chip is industrial or extended. > > > Take > > > > a read if you get a chance... > > > > > > > > BAJ > > > > > > > > -- > > > > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > > > > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > > > > > > > > > > > > > > > > > > -- > > > http://www.piclist.com hint: To leave the PICList > > > mailto:piclist-unsubscribe-request@mitvma.mit.edu > > > > > > > > > > > > > -- > > http://www.piclist.com hint: To leave the PICList > > mailto:piclist-unsubscribe-request@mitvma.mit.edu > > > > -- > > http://www.piclist.com hint: To leave the PICList > > mailto:piclist-unsubscribe-request@mitvma.mit.edu > > > > -- > http://www.piclist.com hint: To leave the PICList > mailto:piclist-unsubscribe-request@mitvma.mit.edu > > > -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu