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. What is a good source for fundimental frequency crystals. I purchased all the ones Im using from digikey. I just started picking crystals. ----- Original Message ----- From: "Jim" To: Sent: Saturday, August 03, 2002 5:02 PM Subject: Re: [PIC]:Has any one ever got a PIC 18F244 chip to work at 40mhz > Are you sure that any of your "over 20 MHz crystals" > are fundamental crystrals at this "over 20 MHz" > frequency? > > Odds are, that all those "higher-frequency crystals" > are actually "overtone" crystals and as such their > "overtone frequency" is stamped on the outside. > > I would then place money on a bet that the simple > little oscillator used on the PIC chips *only* > oscillates at the lower "fundamental" frequency > of those crystals ... > > (All this comes from the perspective of a radio engineer > who has done work with crystals in communications gear > in the (now-distant) past ...) > > RF Jim > > > ----- Original Message ----- > From: "Michael Simpson" > To: > Sent: Saturday, August 03, 2002 1:44 PM > Subject: Re: [PIC]:Has any one ever got a PIC 18F244 chip to work at 40mhz > > > > Done that, did that. I have about 100 crystal,cap and resonators. I > tried > > using the HS/PLL option. Cant get it to go above 20mhz. > > > > ----- Original Message ----- > > From: "M. Adam Davis" > > To: > > Sent: Saturday, August 03, 2002 9:05 AM > > Subject: Re: [PIC]:Has any one ever got a PIC 18F244 chip to work at 40mhz > > > > > > > You'll note, if you inspect the datasheet, that Microchip hasn't listed > > > any values for oscillators (crystal or resonator) above 20MHz, the > > > closest they get is listing a 25MHz crystal in the capacitor value table > > > with valuse of "TBD" as in the capacitor column > > > > > > I seem to remember that if you wanted to run the chip above 20MHz you > > > had to use a lower oscillator value and use the PLL to multiply it by 4. > > > > > > However, you can probably get it going faster if you try a few different > > > capacitors, and perhaps use a resistor in series. Check the archives > > > for crystal problems. > > > > > > -Adam > > > > > > Michael Simpson wrote: > > > > > > >I have tried everything including the HS/PLL option using just about > > every Resonator and Crystal I could get my hands on. > > > > > > > >Im using MPLAB and a PICSTART Plus. > > > > > > > >The best I seem to do is 20Mhz > > > > > > -- > 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#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body