|
Hello, I am venturing into making a first circuit for a wind turbine controller based around the MC9S12DG256 or MC9S12A256 with a Pierce oscillator. Would anyone be able to give me some feedback on the layout? In the device guide, Motorola says the tracks to the oscillator quartz should be made as short as possible, so I came up with two versions, one with shorter leads at the expense of needing a few extra vias to route the adjacent pins out from under the MCU, and the other avoiding these vias, but resulting in longer tracks to the quartz. I would also be grateful for any recommendation of a particular 16 MHz quartz and indicate suitable capacitor and resistor values to go use with it. Many thanks in advance! Robert Imhoff 1) layout with shortest tracks: http://www.issole.info/shorter.gif 2) layout avoiding vias: http://www.issole.info/longer.gif |
|
|
HCS12 Oscillator circuit
Started by ●February 22, 2004
Reply by ●February 22, 20042004-02-22
|
Robert, Please not that early MC9S12DG256 or MC9S12A256 mask-sets don't support the Pierce crystal configuration, but only Colpitts crystal or an external clock driver with 2.5V square wave. Only the newest mask-set 0L91N (or newer one if there are any) of the MC9S12DG256 or MC9S12A256, supports also the Pierce crystal configuration. I suggest you make sure you can get this latest mask-set before designing a Pierce Oscillator for it. The Pierce crystal configuration IS supported by other HCS12 parts like for example DP512 / A512, DT128 / A128 and DJ64 / A64. The Pierce oscillator in general is less susceptible to noise and is more robust than the Colpitts crystal, since it has a higher voltage swing. It is therefore less sensitive to distance from the CPU and vias, than the Colpitts configuration. In your particular case, I believe both the shorter and longer layouts would be just fine. I would personally chose the shortest, since it has all the crystal components on the opposite side from the CPU, and also most of the the crystal system traces. It seems to me this may reduce the radiated influence of the other CPU signals on the crystal signals and vise-versa. But again, in your case, I believe it doesn't matter much, and both layouts would do just fine. Hope this helps, Doron Nohau Corporation HC12 In-Circuit Emulators www.nohau.com/emul12pc.html At 10:19 22/02/2004 +0100, you wrote: >Hello, > >I am venturing into making a first circuit for a wind turbine >controller based around the MC9S12DG256 or MC9S12A256 with a Pierce >oscillator. >Would anyone be able to give me some feedback on the layout? >In the device guide, Motorola says the tracks to the oscillator quartz >should be made as short as possible, so I came up with two versions, >one with shorter leads at the expense of needing a few extra vias to >route the adjacent pins out from under the MCU, and the other avoiding >these vias, but resulting in longer tracks to the quartz. > >I would also be grateful for any recommendation of a particular 16 MHz >quartz and indicate suitable capacitor and resistor values to go use >with it. > >Many thanks in advance! >Robert Imhoff > >1) layout with shortest tracks: http://www.issole.info/shorter.gif > >2) layout avoiding vias: http://www.issole.info/longer.gif > >--------------------To learn more >about Motorola Microcontrollers, please visit >http://www.motorola.com/mcu >o learn more about Motorola Microcontrollers, please visit >http://www.motorola.com/mcu > >Yahoo! Groups Links > > |
|
|
Reply by ●February 22, 20042004-02-22
|
Dear Doron Many thanks for your advice! (I noted your previous messages about the older mask sets, so will make sure of that). Best regards Robert On 22. Feb 2004, at 11:37, Doron Fael wrote: > > Robert, > > Please not that early MC9S12DG256 or MC9S12A256 mask-sets don't > support the > Pierce crystal configuration, but only Colpitts crystal or an external > clock driver with 2.5V square wave. > > Only the newest mask-set 0L91N (or newer one if there are any) of the > MC9S12DG256 or MC9S12A256, supports also the Pierce crystal > configuration. > I suggest you make sure you can get this latest mask-set before > designing a > Pierce Oscillator for it. > > The Pierce crystal configuration IS supported by other HCS12 parts > like for > example DP512 / A512, DT128 / A128 and DJ64 / A64. > > The Pierce oscillator in general is less susceptible to noise and is > more > robust than the Colpitts crystal, since it has a higher voltage swing. > It > is therefore less sensitive to distance from the CPU and vias, than the > Colpitts configuration. > > In your particular case, I believe both the shorter and longer layouts > would be just fine. I would personally chose the shortest, since it > has all > the crystal components on the opposite side from the CPU, and also > most of > the the crystal system traces. It seems to me this may reduce the > radiated > influence of the other CPU signals on the crystal signals and > vise-versa. > But again, in your case, I believe it doesn't matter much, and both > layouts > would do just fine. > > Hope this helps, > Doron > Nohau Corporation > HC12 In-Circuit Emulators > www.nohau.com/emul12pc.html > > At 10:19 22/02/2004 +0100, you wrote: >> Hello, >> >> I am venturing into making a first circuit for a wind turbine >> controller based around the MC9S12DG256 or MC9S12A256 with a Pierce >> oscillator. >> Would anyone be able to give me some feedback on the layout? >> In the device guide, Motorola says the tracks to the oscillator quartz >> should be made as short as possible, so I came up with two versions, >> one with shorter leads at the expense of needing a few extra vias to >> route the adjacent pins out from under the MCU, and the other avoiding >> these vias, but resulting in longer tracks to the quartz. >> >> I would also be grateful for any recommendation of a particular 16 MHz >> quartz and indicate suitable capacitor and resistor values to go use >> with it. >> >> Many thanks in advance! >> Robert Imhoff >> >> 1) layout with shortest tracks: http://www.issole.info/shorter.gif >> >> 2) layout avoiding vias: http://www.issole.info/longer.gif |
Reply by ●February 23, 20042004-02-23
|
Hi
I found the colpits oscillator works just fine, you layouts could be adapted to
get the same result. The extra precaution recomended is to have no ground or
power plane under the crystal pins compared with the pierce oscilator. My
circuit includes the capacitor in the 0V lead of the crystal, and the pcb layout
is modified to put the crystal and pll components on the same side of the pcb as
the processor. By comparison I moved tracks from pins 49..55 to inside the area
enclosed by the processor, I did not as you have break up the ground plane, and
the pll's parts rotated to make it a bit tidier.
Andrew Lohmann AIIE 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 ----- Original Message ----- From: Robert Imhoff To: Sent: Sunday, February 22, 2004 10:53 AM Subject: Re: [68HC12] HCS12 Oscillator circuit *** This e-mail has been modified by Finjan's SurfinGate for E-Mail. *** More details can be found in the attached file, SurfinGate Notification.txt Dear Doron Many thanks for your advice! (I noted your previous messages about the older mask sets, so will make sure of that). Best regards Robert On 22. Feb 2004, at 11:37, Doron Fael wrote: > > Robert, > > Please not that early MC9S12DG256 or MC9S12A256 mask-sets don't > support the > Pierce crystal configuration, but only Colpitts crystal or an external > clock driver with 2.5V square wave. > > Only the newest mask-set 0L91N (or newer one if there are any) of the > MC9S12DG256 or MC9S12A256, supports also the Pierce crystal > configuration. > I suggest you make sure you can get this latest mask-set before > designing a > Pierce Oscillator for it. > > The Pierce crystal configuration IS supported by other HCS12 parts > like for > example DP512 / A512, DT128 / A128 and DJ64 / A64. > > The Pierce oscillator in general is less susceptible to noise and is > more > robust than the Colpitts crystal, since it has a higher voltage swing. > It > is therefore less sensitive to distance from the CPU and vias, than the > Colpitts configuration. > > In your particular case, I believe both the shorter and longer layouts > would be just fine. I would personally chose the shortest, since it > has all > the crystal components on the opposite side from the CPU, and also > most of > the the crystal system traces. It seems to me this may reduce the > radiated > influence of the other CPU signals on the crystal signals and > vise-versa. > But again, in your case, I believe it doesn't matter much, and both > layouts > would do just fine. > > Hope this helps, > Doron > Nohau Corporation > HC12 In-Circuit Emulators > www.nohau.com/emul12pc.html > > At 10:19 22/02/2004 +0100, you wrote: >> Hello, >> >> I am venturing into making a first circuit for a wind turbine >> controller based around the MC9S12DG256 or MC9S12A256 with a Pierce >> oscillator. >> Would anyone be able to give me some feedback on the layout? >> In the device guide, Motorola says the tracks to the oscillator quartz >> should be made as short as possible, so I came up with two versions, >> one with shorter leads at the expense of needing a few extra vias to >> route the adjacent pins out from under the MCU, and the other avoiding >> these vias, but resulting in longer tracks to the quartz. >> >> I would also be grateful for any recommendation of a particular 16 MHz >> quartz and indicate suitable capacitor and resistor values to go use >> with it. >> >> Many thanks in advance! >> Robert Imhoff >> >> 1) layout with shortest tracks: http://www.issole.info/shorter.gif >> >> 2) layout avoiding vias: http://www.issole.info/longer.gif |
|
|
Reply by ●February 23, 20042004-02-23
|
Also note that Colpitts oscillator has a maximum of 16MHz while Pierce supports up to 40MHz (Table A-15 i Device User Guide). --- In , "Andrew Lohmann's New Email Server" <andrew.lohmann@b...> wrote: > Hi > I found the colpits oscillator works just fine, you layouts could be adapted to get the same result. The extra precaution recomended is to have no ground or power plane under the crystal pins compared with the pierce oscilator. My circuit includes the capacitor in the 0V lead of the crystal, and the pcb layout is modified to put the crystal and pll components on the same side of the pcb as the processor. By comparison I moved tracks from pins 49..55 to inside the area enclosed by the processor, I did not as you have break up the ground plane, and the pll's parts rotated to make it a bit tidier. > > > Andrew Lohmann AIIE > Design Engineer > > PLEASE NOTE NEW EMAIL ADDRESS IS: > andrew.lohmann@b... > > 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 > ----- Original Message ----- > From: Robert Imhoff > To: > Sent: Sunday, February 22, 2004 10:53 AM > Subject: Re: [68HC12] HCS12 Oscillator circuit > *** This e-mail has been modified by Finjan's SurfinGate for E-Mail. > *** More details can be found in the attached file, SurfinGate Notification.txt > Dear Doron > > Many thanks for your advice! > (I noted your previous messages about the older mask sets, so will make > sure of that). > > Best regards > Robert > > On 22. Feb 2004, at 11:37, Doron Fael wrote: > > > > > Robert, > > > > Please not that early MC9S12DG256 or MC9S12A256 mask-sets don't > > support the > > Pierce crystal configuration, but only Colpitts crystal or an external > > clock driver with 2.5V square wave. > > > > Only the newest mask-set 0L91N (or newer one if there are any) of the > > MC9S12DG256 or MC9S12A256, supports also the Pierce crystal > > configuration. > > I suggest you make sure you can get this latest mask-set before > > designing a > > Pierce Oscillator for it. > > > > The Pierce crystal configuration IS supported by other HCS12 parts > > like for > > example DP512 / A512, DT128 / A128 and DJ64 / A64. > > > > The Pierce oscillator in general is less susceptible to noise and is > > more > > robust than the Colpitts crystal, since it has a higher voltage swing. > > It > > is therefore less sensitive to distance from the CPU and vias, than the > > Colpitts configuration. > > > > In your particular case, I believe both the shorter and longer layouts > > would be just fine. I would personally chose the shortest, since it > > has all > > the crystal components on the opposite side from the CPU, and also > > most of > > the the crystal system traces. It seems to me this may reduce the > > radiated > > influence of the other CPU signals on the crystal signals and > > vise-versa. > > But again, in your case, I believe it doesn't matter much, and both > > layouts > > would do just fine. > > > > Hope this helps, > > Doron > > Nohau Corporation > > HC12 In-Circuit Emulators > > www.nohau.com/emul12pc.html > > > > At 10:19 22/02/2004 +0100, you wrote: > >> Hello, > >> > >> I am venturing into making a first circuit for a wind turbine > >> controller based around the MC9S12DG256 or MC9S12A256 with a Pierce > >> oscillator. > >> Would anyone be able to give me some feedback on the layout? > >> In the device guide, Motorola says the tracks to the oscillator quartz > >> should be made as short as possible, so I came up with two versions, > >> one with shorter leads at the expense of needing a few extra vias to > >> route the adjacent pins out from under the MCU, and the other avoiding > >> these vias, but resulting in longer tracks to the quartz. > >> > >> I would also be grateful for any recommendation of a particular 16 MHz > >> quartz and indicate suitable capacitor and resistor values to go use > >> with it. > >> > >> Many thanks in advance! > >> Robert Imhoff > >> > >> 1) layout with shortest tracks: http://www.issole. info/shorter.gif > >> > >> 2) layout avoiding vias: http://www.issole.info/longer.gif > > |
|
|
Reply by ●February 24, 20042004-02-24
|
Hello How does one choose the optimal crystal frequency for the HCS12 (e.g. MC9S12DG256)? Was wondering with Andrew Lohman, why do the evbs like the one from Technological Arts or CardS12 from Elektronikladen use 16 MHz crystals, when it would seem like the circuit would be more stable with a lower frequency crystal, say around 4 MHz and then using the PLL to obtain the desired clock? Many thanks for any insights! Robert Imhoff |
|
|
Reply by ●February 24, 20042004-02-24
|
Robert, You are right. Most applications use a 4MHz or 8MHz crystal and then use the internal PLL to up the frequency. This prevents having high clock signals externally, and creates a more robust crystal circuit, especially if the Colpitts configuration is used. I think the EVBs use a higher frequency crystal since most beginners will not use the internal PLL at first, and so a higher frequency crystal is handy then to supply reasonable processing power, and to allow the serial-port debuggers to work at a reasonable frequency. Hope this helps, Doron Nohau Corporation HC12 In-Circuit Emulators www.nohau.com/emul12pc.html At 17:03 24/02/2004 +0100, you wrote: >Hello > >How does one choose the optimal crystal frequency for the HCS12 (e.g. >MC9S12DG256)? > >Was wondering with Andrew Lohman, why do the evbs like the one from >Technological Arts or CardS12 from Elektronikladen use 16 MHz crystals, >when it would seem like the circuit would be more stable with a lower >frequency crystal, say around 4 MHz and then using the PLL to obtain >the desired clock? > >Many thanks for any insights! >Robert Imhoff |
Reply by ●February 24, 20042004-02-24
|
Robert Imhoff <> wrote: > How does one choose the optimal crystal frequency for the HCS12 (e.g. > MC9S12DG256)? With 4MHz...8MHz, you can use rather large capacitors without overloading the crystal (or the oscillator amplifier), therefore parasitic capacitance doesn't influence the design and you get a pretty stable and reliable oscillator. Lower frequencies make the PLL response slower and probably cause more jitter. Initial BDM speed is very low. > Was wondering with Andrew Lohman, why do the evbs like the one from > Technological Arts or CardS12 from Elektronikladen use 16 MHz crystals, maybe to achieve good BDM speed. Most BDM Flash programming stuff can't use the PLL. Gordon's programmer can (IIRC), iSYSTEM can't. What about Nohau, P&E? Oliver -- Oliver Betz, Muenchen |
|
|
Reply by ●February 25, 20042004-02-25
|
At 20:30 2/25/2004, you wrote: >Can someone suggest a manufacture for a crystal or oscillator in the 16 >MHz range? We usually buy our crystals/oscillators from Murata and they >have a 12 week lead time. For limited scale production runs we've been using ECS, both crystals and oscillators (all 16 MHz in our case). Delivery has been excellent. And there is always Digikey which carries them, with virtually overnight delivery. ----------- James M. Knox TriSoft ph 512-385-0316 1109-A Shady Lane fax 512-366-4331 Austin, Tx 78721 ----------- |
Reply by ●February 25, 20042004-02-25
|
Hi,
Some of the S12's include a pre-loaded bootloader, so the lower clock speed
which affects down load time could be mittigated by programming lot's of
target's at one time surely? The advantage of using the lowest practicle crystal frequency, and the lower power Colipits oscillator configuration is that potentially troublesome harmonics of the crystal frequency that could be radiated are minimised. I get 15,974,400Hz from 3,686,400 Hz (crystal) / 3 * 13. I picked the lowest convenient frequency that suits RS232 baudrate generation. As too the speed change, I think the P&E with Cosmic Zap programmes at initial bus speed. You you would probably need to BDM load a small bootloader which configured the pll and switched speed before downloading the bulk of your application by serial or whatever. To acheive that in most cases? Andrew Lohmann AIIE 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 ----- Original Message ----- From: Oliver Betz To: Sent: Tuesday, February 24, 2004 4:57 PM Subject: Re: [68HC12] HCS12 Oscillator circuit frequency *** This e-mail has been modified by Finjan's Vital Security for E-Mail. *** More details can be found in the attached file, Vital Security Notification.html Robert Imhoff <> wrote: > How does one choose the optimal crystal frequency for the HCS12 (e.g. > MC9S12DG256)? With 4MHz...8MHz, you can use rather large capacitors without overloading the crystal (or the oscillator amplifier), therefore parasitic capacitance doesn't influence the design and you get a pretty stable and reliable oscillator. Lower frequencies make the PLL response slower and probably cause more jitter. Initial BDM speed is very low. > Was wondering with Andrew Lohman, why do the evbs like the one from > Technological Arts or CardS12 from Elektronikladen use 16 MHz crystals, maybe to achieve good BDM speed. Most BDM Flash programming stuff can't use the PLL. Gordon's programmer can (IIRC), iSYSTEM can't. What about Nohau, P&E? Oliver -- Oliver Betz, Muenchen --------------------To learn more about Motorola Microcontrollers, please visit http://www.motorola.com/mcu o learn more about Motorola Microcontrollers, please visit http://www.motorola.com/mcu ------ Yahoo! Groups Links a.. To |
