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Hi, I'm designing a board for a uni project using the MC9S12DP512 part. Everything is coming along well, except I've got a few questions about the oscillator side of things. 1. I'd like to connect the oscillator using the Colpitts configuration, and I'm not exactly sure how to calculate the value of Cdc (to remove the DC bias). I intend to use a 12MHz C-MAC crystal (http://www.farnell.com/datasheets/24586.pdf) any suggestions on how I should go about calculating the correct value for this, or the other two capacitors for that matter (22pF comes to mind for no apparent reason)? 2. In the Microcontroller selection guide document, the operating frequency of the MC9S12DP512 is listed as '25,33'. Does this mean that this part officially supports a bus speed of 33MHz? 3. Once I get things up and running, I wouldn't mind playing around with the PLL to boost the bus speed up a bit. With regards to the XFC pin and calculating the values of the resistors and capacitors, I can't seem to see the program on the Freescale site that is to be used. Can anyone point me in the right direction? Cheers, -Kent

Re: MC9S12DP512 oscillator questions
Re: MC9S12DP512 oscillator questions


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I use 1nF in the ground lead of the crystal, which gives you a nice board layout. There is an app note on the other capacitors I use a 3.6864MHz crystal with a 33p between EXTAL and XTAL, and 10p between XTAL and GND. It is good practice to keep the crystal frequency down, and use the VCO. Andrew Lohmann AMIIE Design Engineer PLEASE NOTE NEW EMAIL ADDRESS IS: Bellingham + Stanley Ltd. Longfield Road, Tunbridge Wells, Kent, TN2 3EY, England. Tel: +44 (0) 1892 500400 Fax: +44 (0) 1892 543115 Website: www.bs-ltd.com Kent Williams wrote: > Hi, > > I'm designing a board for a uni project using the MC9S12DP512 part. > Everything is coming along well, except I've got a few questions about > the oscillator side of things. > > 1. I'd like to connect the oscillator using the Colpitts configuration, > and I'm not exactly sure how to calculate the value of Cdc (to remove > the DC bias). I intend to use a 12MHz C-MAC crystal > (http://www.farnell.com/datasheets/24586.pdf) > <http://www.farnell.com/datasheets/24586.pdf%29> any suggestions on how I > should go about calculating the correct value for this, or the other two > capacitors for that matter (22pF comes to mind for no apparent reason)? > 2. In the Microcontroller selection guide document, the operating > frequency of the MC9S12DP512 is listed as '25,33'. Does this mean that > this part officially supports a bus speed of 33MHz? > 3. Once I get things up and running, I wouldn't mind playing around with > the PLL to boost the bus speed up a bit. With regards to the XFC pin and > calculating the values of the resistors and capacitors, I can't seem to > see the program on the Freescale site that is to be used. Can anyone > point me in the right direction? > > Cheers, > -Kent > *Yahoo! Groups Sponsor* > ADVERTISEMENT > click here > <http://us.ard.yahoo.com/SIG=129ukk2dc/M=298184.6191685.7192823.3001176/D=groups/S=1706554205:HM/EXP=1111663827/A=2593423/R=0/SIG=11el9gslf/*http://www.netflix.com/Default?mqso=60190075 > > ------------------------------------------------------------------------ > *>. -----------------------------Disclaimer----------------------------- This communication contains information which is confidential and may also be privileged. It is for the exclusive use of the addressee. If you are not the addressee please note that any distribution, reproduction, copying, publication or use of this communication or the information is prohibited. If you have received this communication in error, please contact us immediately and also delete the communication from your computer. We accept no liability for any loss or damage suffered by any person arising from use of this e-mail. -----------------------------Disclaimer----------------------------- [Non-text portions of this message have been removed]

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Hello Kent, See some answers below. Hope this helps, Doron Nohau HC12 In-Circuit Emulators www.nohau.com/emul12pc.html At 22:30 23/03/2005 +1100, you wrote: >Hi, > >I'm designing a board for a uni project using the MC9S12DP512 part. >Everything is coming along well, except I've got a few questions about >the oscillator side of things. > >1. I'd like to connect the oscillator using the Colpitts configuration, >and I'm not exactly sure how to calculate the value of Cdc (to remove >the DC bias). I intend to use a 12MHz C-MAC crystal >(http://www.farnell.com/datasheets/24586.pdf) any suggestions on how I >should go about calculating the correct value for this, or the other two >capacitors for that matter (22pF comes to mind for no apparent reason)? If I remember correctly, there were some suggestion about the subject in this list in the past. You may want to look through the archive on yahoo for information. >2. In the Microcontroller selection guide document, the operating >frequency of the MC9S12DP512 is listed as '25,33'. Does this mean that >this part officially supports a bus speed of 33MHz? At some point Freescale (at the time still Motorola) considered releasing a 33MHz version of the MC9S12DP512. To the best of my knowledge this plan was not concluded, mainly because of the new S12X family that now runs to 40MHz bus-speed already from the design phase, with no need to do a special speed-screen for 33MHz MC9S12DP512 parts. Thus the MC9S12DP512 is only specified for 25MHz bus-speed operation over the full automotive temperature range (-40 to +125 C). In room temperature most likely you can run it to 33MHz bus speed (although it is not guaranteed to run well in that speed by Freescale). I run it at that speed from time to time, to test how fast I can push our HCS12 emulator, so I know it does work at 33MHz. >3. Once I get things up and running, I wouldn't mind playing around with >the PLL to boost the bus speed up a bit. With regards to the XFC pin and >calculating the values of the resistors and capacitors, I can't seem to >see the program on the Freescale site that is to be used. Can anyone >point me in the right direction? You can find the Xfc calculator on the Nohau web-site at the above link in my signature (click on "HCS12 Family PLL Circuit Calculator") : >Cheers, >-Kent > > >Yahoo! Groups Links [Non-text portions of this message have been removed]

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