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linux123
Joined: 09 Oct 2006
Posts: 17
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| 400MHz with PLL |
 Posted: Tue Dec 05, 2006 12:51 pm |
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Hy people
I need of cristal 400MHz, and talk-me to contruct with PLL, but i do no make, i need help.
Thanks. |
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SherpaDoug
Joined: 07 Sep 2003
Posts: 1640
Location: Cape Cod Mass USA
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| Posted: Tue Dec 05, 2006 1:36 pm |
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I think you want to run a PIC at 40MHz. There are not any PICs that can do 400MHz. If you want 40MHz you need a 10MHz crystal and the PLL will multiply the speed by 4.
What PIC are you using?
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The search for better is endless. Instead simply find very good and get the job done. |
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linux123
Joined: 09 Oct 2006
Posts: 17
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| ok |
| Posted: Wed Dec 06, 2006 1:38 pm |
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Itīs problem, because the project run cristal of 400MHz and 200Mhz.
other MCU type TEXAS run 400MHz in PLL.
The men of this project talk-me of use LMX1600 (National) and MCU to generate 400MHz. |
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Konrad
Joined: 15 Sep 2003
Posts: 34
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| Check the LMX2326 driver |
| Posted: Wed Dec 06, 2006 3:25 pm |
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CCS provide an example driver, LMX2326, which is very similar.
You just need a small PIC e.g. 12F635
I assume you are at home with RF synths and it is just the MCU you are asking about.
Alternatively, use codeloader for development and just copy the codes. |
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linux123
Joined: 09 Oct 2006
Posts: 17
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| ok. |
| Posted: Thu Dec 07, 2006 7:12 am |
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Ok, how pin go my circuit, and anybody help-me in code to PIC load of 400Mhz ?
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rwyoung
Joined: 12 Nov 2003
Posts: 563
Location: Lawrence, KS USA
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| Re: ok |
| Posted: Thu Dec 07, 2006 10:38 am |
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| linux123 wrote: | Itīs problem, because the project run cristal of 400MHz and 200Mhz.
other MCU type TEXAS run 400MHz in PLL.
The men of this project talk-me of use LMX1600 (National) and MCU to generate 400MHz. |
The LMX1600 is pretty straight forward as far as programming goes. It has Microwire serial interface for setting parameters. It is an 18-bit control word. Page 7 of the data sheet starts outlining the bit functions.
Beyond this, I don't understand your question. Are you looking to use a PIC (or any microcontroller) to control the LMX1600 or similar programmalble PLL or are you trying to clock a microcontroller at 400MHz?
If you just want to control the LMX1600 or similar, you need to read that part's datasheet carefully with respect to its control interface and then study the appropriate functions on the PIC. In this case, using the CCS compiler, I could skip the SPI functions and just manipulate the clock, data and LE lines with the OUTPUT functions.
If you are trying to run a Microcontroller at 400MHz, good luck with that. I dont' know of any that use an external crystal speed of 400MHz except possibly some of the Blackfin parts but even those I believ you use a much lower frequency and it has its own internal PLL that revs things up to >100MIPs.
Obviously English is not your first language but please try to be as specific as possible. It will definately help.
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Rob Young
The Screw-Up Fairy may just visit you but he has crashed on my couch for the last month! |
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rwyoung
Joined: 12 Nov 2003
Posts: 563
Location: Lawrence, KS USA
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| Re: ok. |
| Posted: Thu Dec 07, 2006 10:43 am |
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| linux123 wrote: | Ok, how pin go my circuit, and anybody help-me in code to PIC load of 400Mhz ?
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74AS logic is pretty hot stuff but I seriously doubt it will work reliably at 400MHz. That is a 2.5ns period and the 74AS04 at 5V is 3ns minimum for low to high transitions best case, 11ns worst case per the TI datasheet.
If you are lucky, the inverter will run in an unsaturated mode and produce a craptacular sinewave but the 74AS08 won't help much as it doesn't have Schmidt trigger inputs and its rise/fall times won't be any better than the 74AS04.
And don't even think about running with less than a 5V supply using 74AS logic, it doesn't work for a damn.
_________________
Rob Young
The Screw-Up Fairy may just visit you but he has crashed on my couch for the last month! |
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linux123
Joined: 09 Oct 2006
Posts: 17
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| yes |
| Posted: Thu Dec 07, 2006 11:07 am |
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| I am of Brazil. I have this project that it needs a crystal of 400MHz (as this in the figure above). The constructor of the circuit informed me to use the LMX1600 together with a MCU to obtain this speed, therefore crystal of 400MHz does not exist. |
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rwyoung
Joined: 12 Nov 2003
Posts: 563
Location: Lawrence, KS USA
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| Re: yes |
| Posted: Fri Dec 08, 2006 8:22 am |
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| linux123 wrote: | | I am of Brazil. I have this project that it needs a crystal of 400MHz (as this in the figure above). The constructor of the circuit informed me to use the LMX1600 together with a MCU to obtain this speed, therefore crystal of 400MHz does not exist. |
OK, now we are getting somewhere... :-)
Definately read the LMX1600 datasheet VERY CAREFULLY. I have no idea if the datasheets are available in other languages besides English, maybe you can contact a local National Semiconductor distributor to find out if they have translations. That might be helpful.
Some key items:
1) Both the LMX1600 and MCU should run from 3.3V if possible. While the datasheet does imply the LMX1600 can tolerate Vcc=5V, it isn't recomended for correct operation.
2) If you have NO experience with PICs, this might not be the best time to learn. If your project can tolerate the cost, consider getting a pre-built PIC module such as the Basic Stamp family from Parallax and using its PicBasic interpreter. Might be easier for a one-off project. But keep in mind the Vcc=3.3V issue or be prepaired to add level translators/buffers for your control signals.
3) Select your crystal for the LMX1600 to be between 1 and 20MHz or use a TXCO between 1 and 40MHz but remember you will need to configure the multipliers in the LMX1600 as well as its crystal drive appropriately. Although you could share clock sources between the LMX1600 and the PIC, I wouldn't in your case for the sake of simplicity. Keep in mind that the "quality" of your output frequency (jitter, etc) will be affected by the quality of your reference clock. A TXCO will likely be better than a naked crystal in this respect.
4) Don't forget about the LMX1600's ENaux and ENmain for power controll. These can be controlled by the PIC or simply tied to active states.
5) The LMX1600 uses MicroWire which is very similar to SPI but rather than use the CCS SPI functions (if you decide to use CCS) I would "bit-bang" the port since the control word is something like 18-bits long. For somebody with no PIC experience, figuring out how to use the serial engines and work around some of the CCS bugs can be very frustrating.
Good luck! You have a LOT of reading to do before you solder the first pin or type the first line of a program!
_________________
Rob Young
The Screw-Up Fairy may just visit you but he has crashed on my couch for the last month! |
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