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Si502 or Si503 — Parallax Forums

Si502 or Si503

TCTC Posts: 1,019
edited 2014-05-17 16:44 in Propeller 1
Hello all,

I'm taking a little breather from the oven, and I came up with the idea to rebuild my DIY prop prototyping board. But this time, better. I never accounted for a way to change clock frequencies on my current design, but I want it on my next. So I want to go with either Silicon Laboratories Si502 or Si503. And use a SPDT switch for the Si502, or a SP4T for the Si503. That would give me the option of different frequencies with the flick of a switch.

I would have 5Mhz and 6.25Mhz set for 2 of the frequencies.

My questions are;

Do you agree with my frequency choices?

Do you think I should go with the Si502 and only have 2 choices, or do you think I should go with the Si503 and have 4 choices?

If I went with the Si503, What do you think the other 2 frequencies should be?

Thanks
TC

Comments

  • kwinnkwinn Posts: 8,697
    edited 2014-05-15 19:30
    Go with the Si503 and have 4 choices. More choice is better. Consider using 2 prop pins instead of or with a switch so you can control it with software, or using a Si504 so you can program it for any frequency.
  • TCTC Posts: 1,019
    edited 2014-05-16 01:40
    kwinn wrote: »
    Go with the Si503 and have 4 choices. More choice is better. Consider using 2 prop pins instead of or with a switch so you can control it with software, or using a Si504 so you can program it for any frequency.

    I agree, more choices are better. I was thinking of the Si504, but from what I can tell from the datasheet is it must be initialized first. And I looked on OBEX and the forums and could not find an object that control it.

    What would be the need to have software control, when this is only going to be for prototyping projects?
  • kwinnkwinn Posts: 8,697
    edited 2014-05-16 20:27
    The data sheet for the 504 says "The Si504 starts up in the user’s ordered preconfiguration" so if you wanted to use it in place of the propeller crystal you could do that by getting one preconfigured to start up at 5MHz or there about.

    Whether you need to have software control or not depends on what sort of prototyping you are doing.

    If all you want to do is run the propeller at some of the popular frequencies (80, 96, 100MHz) a 503 configured for those frequencies would be a good choice.

    If you are building a prototyping system that will be used for future projects you may want a wider range of adjustment. If you are doing high speed data acquisition or signal generation it can be very helpful to have the propeller run at a clock speed that is a multiple of the signal rate. For that the 504 would be better.
    TC wrote: »
    I agree, more choices are better. I was thinking of the Si504, but from what I can tell from the datasheet is it must be initialized first. And I looked on OBEX and the forums and could not find an object that control it.

    What would be the need to have software control, when this is only going to be for prototyping projects?
  • jmgjmg Posts: 15,173
    edited 2014-05-16 22:46
    kwinn wrote: »
    The data sheet for the 504 says "The Si504 starts up in the user’s ordered preconfiguration" so if you wanted to use it in place of the propeller crystal you could do that by getting one preconfigured to start up at 5MHz or there about.

    Yes, the Si504 powers-up with a default preset value, you define when you order them.
    After that, you can change them.

    Check the exact part codes when ordering from Digikey, as ones I got tagged by Digikey as100MHz, stopped at 80MHz.
    When I back-checked the SiLabs Data-sheet part-letters, they were just 80MHz parts.
  • TCTC Posts: 1,019
    edited 2014-05-17 03:00
    kwinn wrote: »

    Whether you need to have software control or not depends on what sort of prototyping you are doing.

    If all you want to do is run the propeller at some of the popular frequencies (80, 96, 100MHz) a 503 configured for those frequencies would be a good choice.

    I am so sorry I forgot that information. This project would be for simple hook ups, and proof of concept mostly. It will allow me to experiment quickly and easily.
    If you are building a prototyping system that will be used for future projects you may want a wider range of adjustment. If you are doing high speed data acquisition or signal generation it can be very helpful to have the propeller run at a clock speed that is a multiple of the signal rate. For that the 504 would be better.

    That makes sense, thank you.

    jmg wrote: »
    Yes, the Si504 powers-up with a default preset value, you define when you order them.
    After that, you can change them.

    Check the exact part codes when ordering from Digikey, as ones I got tagged by Digikey as100MHz, stopped at 80MHz.
    When I back-checked the SiLabs Data-sheet part-letters, they were just 80MHz parts.

    I'm glad you said something, because I would've never noticed. Thank you.
  • TubularTubular Posts: 4,703
    edited 2014-05-17 16:37
    This is a little 504 breakout board I'm waiting on, TC
    http://oshpark.com/shared_projects/WAZu9LQ7

    I have the chips (nominal 5MHz like a standard xtal, adjust from there. Should the PCBs later this week, and then I'll have a go at a C1D driver for it. Jmg has provided some tips
  • TCTC Posts: 1,019
    edited 2014-05-17 16:44
    Tubular wrote: »
    This is a little 504 breakout board I'm waiting on, TC
    http://oshpark.com/shared_projects/WAZu9LQ7

    I have the chips (nominal 5MHz like a standard xtal, adjust from there. Should the PCBs later this week, and then I'll have a go at a C1D driver for it. Jmg has provided some tips

    That's really cool.

    I'll have to keep my eyes open for your driver, thanks.
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