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SPI speed limitation

Discussion in 'Electronic Design' started by Stijn Goris, May 6, 2004.

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  1. Stijn Goris

    Stijn Goris Guest

    hi all,

    Does SPI serial communication have a speed limitation? I guess so bu I can't
    seem to find information regarding it's speed...

    regards
    Stijn
     
  2. Each device specifies a max clock.
    Lookup the datasheets.

    Rene
     
  3. You have to look in detail at the timing diagrams of the devices on
    the bus and make sure that all are operating within specifications for
    both read and write (if the latter mode is used). That's after you get
    the mode right.

    Best regards,
    Spehro Pefhany
     
  4. Stijn Goris

    Stijn Goris Guest

    I m designing a product for my schoolproject. I want to communicate between
    a processor and a SPI bus. I don't have a specific component in mind but i m
    just wondering if 10Mbit/s communication would be possible with SPI?

    regards
     
  5. So long as you don't have specific components in mind, sure, just
    about anything is possible.

    When you get to real parts, for example, some Atmel EEPROMs are spec'd
    to operate at 10MHz (provided the other timing requirements are met),
    but only at 5V Vdd. At lower Vdd you might be restricted to half that
    or less.

    If you want to communicate with as many different devices as possible,
    I'd suggest 2MHz at 5V Vdd as a good compromise between speed and
    versatility. That's only 4usec to simultaneously send/receive one
    byte, which isn't too bad. You'll eat up a bit more diddling the /CS
    so you get diminishing returns on the SPI clock rate for a fixed
    processor cycle time.

    One exception where you might want to push toward the maximum is
    dragging large amounts of data out of SEEPROMs in
    auto-address-increment mode, where you leave the chip selected for a
    relatively large number of cycles (you just set up the mode and
    address, and keep clocking it, and data keeps coming out like a big
    shift-register until you stop or something glitches). You can also
    dynamically change the clock rate in many cases to allow for chips
    that are slower than others.

    Best regards,
    Spehro Pefhany
     
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