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10 Mhz crystal question — Parallax Forums

10 Mhz crystal question

science_geekscience_geek Posts: 247
edited 2009-01-16 22:20 in Propeller 1
i was wondering if the propellor could be safely run with a 10 Mhz crystal with a clock multiplier of 16, will it get hotter, what about problems with accessing ram(i have read that this can be a problem if you run it to fast)

Comments

  • mynet43mynet43 Posts: 644
    edited 2008-12-26 20:34
    I haven't checked on this for a while but I believe about the best you can do is 6 MHz x 16 which is close to 100 MHz.

    Jim
  • Mike GreenMike Green Posts: 23,101
    edited 2008-12-26 21:49
    The Propeller is spec'd for an 80MHz system clock. It has been commonly used up to 96MHz, but is not guaranteed to function at that speed, particularly at extremes of the temperature and power supply voltage range. Some Propellers have been run faster using refrigeration. The datasheet has graphs showing this. In particular, it's been tested at about 138MHz at a temperature of -55C and a supply voltage of 3.6V.

    Post Edited (Mike Green) : 12/26/2008 9:55:01 PM GMT
  • heaterheater Posts: 3,370
    edited 2008-12-28 13:51
    I use a 10MHz xtal with 8 times multipiler. Never did get it to run with 16 times.

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  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2008-12-28 16:20
    There was a very nice page about this on the Propeller Wiki,
    but someone has done some re-organizing and now I can't located it.

    Anyone got the link?

    OBC

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    Check out: Protoboard Introduction , Propeller Cookbook 1.4 & Software Index
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  • hippyhippy Posts: 1,981
    edited 2009-01-16 19:35
    propeller.wikispaces.com/Oscillator

    The break-point under 'normal operating conditions' seems to be around 120MHz. I've had success and no failures at just short of 120MHz, 7.3728MHz + PLL16x and 14.31818MHz + PLL8x using an unmodified ProtoBoard but others have not had perfect operation.
  • agodwinagodwin Posts: 72
    edited 2009-01-16 21:04
    Has anyone tried with an external source (e.g. a packaged oscillator) instead of the crystal ?
    It may be that the prop will run at higher speed but the oscillator won't, or has a poor output waveform that upsets the prop.
  • LeonLeon Posts: 7,620
    edited 2009-01-16 21:13
    That won't make any difference; the speed limitation is nothing to do with the oscillator input.

    Leon

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  • Mike GreenMike Green Posts: 23,101
    edited 2009-01-16 21:15
    There was some extensive testing done by Parallax and reported in this forum as part of the development of the datasheet.. The worst case logic paths seem to be around the flag registers so running with an external clock won't help.
  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2009-01-16 22:20
    Thanks hippy!

    ...hippy!!? HIPPY's back! Wondering when you might wander back this direction. [noparse]:)[/noparse]

    OBC

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    New to the Propeller?

    Check out: Protoboard Introduction , Propeller Cookbook 1.4 & Software Index
    Updates to the Cookbook are now posted to: Propeller.warrantyvoid.us
    Got an SD card connected? - PropDOS
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