Post by thread:[EE] Source for 40 Mhz Xtal for PIC18F252 ?

Electronics amateur having a bit of trouble finding, 40 Mhz Crystals for use with an 18F252 at its top speed. Would also appreciate any pointers to resonators at this same speed. I need maybe 10-20 of these. For now at least. I'd appreciate it if you could note if you've actually used the given part or if it "should work". thanks! Phil p.s. Extra credit questions.... I did find a catalog entry for 40Mhz "oscillators" from Kyocera in a 14 pin dip sized package for use with "microprocessors"...4 pins...+5 V, Ground, "output", and a do-nothing pin presumably just for mechanical connection to the PCB. $1 each and said to drive CMOS and TTL. Other than size any gotcha's with these? (Power consumption maybe?) Also the 18F252 has a PLL mode where a 10 Mhz crystal is turned into a 40 Mhz signal. My understanding is that this uses more power, and is really there for those concerned about emitting higher frequency interference. I'd consider using it, except I can't find 10 Mhz crystals either! They seem to exist mostly as multiples of 4...comments about this option, or 10 Mhz crystals? -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

> Electronics amateur having a bit of trouble finding, 40 Mhz Crystals > for use with an 18F252 at its top speed. Maybe I'm mistaken, but I thought that you needed a 10 MHz crystal with the PLL set to 4. > Would also appreciate any pointers to resonators at this same speed. Both should be available at Digikey. I've used the resonators. > I need maybe 10-20 of these. For now at least. > Also the 18F252 has a PLL mode where a 10 Mhz crystal is turned into > a 40 Mhz signal. My understanding is that this uses more power, and > is really there for those concerned about emitting higher frequency > interference. I'd consider using it, except I can't find 10 Mhz > crystals either! They seem to exist mostly as multiples of > 4...comments about this option, or 10 Mhz crystals? I had no problem finding 10 or 20 MHz crystals. -- D. Jay Newman ! spam_OUTjayTakeThisOuTsprucegrove.com ! Xander: Giles, don't make cave-slayer unhappy. http://enerd.ws/~jay/ ! -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

> Electronics amateur having a bit of trouble finding, 40 Mhz Crystals > for use with an 18F252 at its top speed. You do know that the 18F's (at least most of them, but that's another story) can use Xtals up to 25 MHz, and can use their *4 internal multiplier to run up to 40 MHz *internally* (which requires a 10 MHz crystal). I guess this cancels your question rather than answering it :) And I will put this in the still very small faq at http://www.voti.nl/picfaq Wouter van Ooijen -- ------------------------------------------- Van Ooijen Technische Informatica: http://www.voti.nl consultancy, development, PICmicro products -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

At 8:37 PM +0200 8/21/03, Wouter van Ooijen wrote: > > Electronics amateur having a bit of trouble finding, 40 Mhz Crystals >> for use with an 18F252 at its top speed. > >You do know that the 18F's (at least most of them, but that's another >story) can use Xtals up to 25 MHz, and can use their *4 internal >multiplier to run up to 40 MHz *internally* (which requires a 10 MHz >crystal). > >I guess this cancels your question rather than answering it :) > >And I will put this in the still very small faq at >http://www.voti.nl/picfaq > >Wouter van Ooijen Aha! Very useful info indeed. I wonder why the references I saw seemed focused on noting how the PLL mode helps reduce RFI and didn't emphasize it is the *only* way to get top speed at all. Thanks! Off to find 10 Mhz Xtals...only 4's and 20's in my stash... Phil -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

That isn't the *only* way to get top speed... external CRYSTAL (HS setting) max speed is 25MHz, but you can still apply a 40MHz clock from an external oscillator (EC or ECIO setting). -Mark At 03:11 PM 8/21/03 -0400, you wrote: {Quote hidden}>At 8:37 PM +0200 8/21/03, Wouter van Ooijen wrote: >> > Electronics amateur having a bit of trouble finding, 40 Mhz Crystals >>> for use with an 18F252 at its top speed. >> >>You do know that the 18F's (at least most of them, but that's another >>story) can use Xtals up to 25 MHz, and can use their *4 internal >>multiplier to run up to 40 MHz *internally* (which requires a 10 MHz >>crystal). >> >>I guess this cancels your question rather than answering it :) >> >>And I will put this in the still very small faq at >>http://www.voti.nl/picfaq >> >>Wouter van Ooijen > > >Aha! Very useful info indeed. I wonder why the references I saw >seemed focused on noting how the PLL mode helps reduce RFI and didn't >emphasize it is the *only* way to get top speed at all. > >Thanks! Off to find 10 Mhz Xtals...only 4's and 20's in my stash... > >Phil > >-- >http://www.piclist.com hint: The list server can filter out subtopics >(like ads or off topics) for you. See http://www.piclist.com/#topics ------------------------------------------- Mark Samuels ARMA Design Tel:(858) 373-1320 x115 Fax:(858) 373-1325 Email: .....markKILLspam@spam@armanet.com Web: http://www.armanet.com The information contained in this electronic message is private and may contain privileged, confidential or inside information. Any distribution, copying or forwarding or use of this communication by anyone other than the intended recipient(s) is strictly prohibited and may be unlawful. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

> except I can't find 10 Mhz crystals either! They seem to > exist mostly as multiples of 4...comments about this > option, or 10 Mhz crystals? I've no trouble finding 10MHz from any number of sources around NZ. A local retail chain (Dick Smith), who STILL stocks the 16F84 as weapon of choice, stocks just 3 crystals - 32k, 4M and 10M (I must tell them about the 628-20 one day) Rather than run the 252 flat out all the time, you speed freak, as well as the 10MHz look around for a 9.8304MHz (also should be easy to find). This will run a x4 252 at 39.3216MHz which is both high speed and a base clock for RS232 -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

At 10:06 AM +1200 8/22/03, Jinx wrote: > > except I can't find 10 Mhz crystals either! They seem to >> exist mostly as multiples of 4...comments about this >> option, or 10 Mhz crystals? > >I've no trouble finding 10MHz from any number of sources >around NZ. A local retail chain (Dick Smith), who STILL >stocks the 16F84 as weapon of choice, stocks just 3 crystals - >32k, 4M and 10M (I must tell them about the 628-20 one day) > >Rather than run the 252 flat out all the time, you speed freak, as >well as the 10MHz look around for a 9.8304MHz (also should be >easy to find). This will run a x4 252 at 39.3216MHz which is >both high speed and a base clock for RS232 I'll admit I didn't look that hard for 10MHz Xtals...I wrongly thought it would be better to use 40MHz ones... The need for speed here is that I have to get a 40 KHz signal out of the hardware PWM unit AND try to retain as close to 10 bits of duty cycle resolution as possible. Phil -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics