Connect with us

Quick Microcontroller question

Discussion in 'Misc Electronics' started by Colin, Aug 26, 2005.

Scroll to continue with content
  1. Colin

    Colin Guest

    With an atmel microcontroller when you write 1 to a pin does the pin
    actually read +5, or is that only when you have an internal pullup on that
    pin?
    Thanks
    Colin
     
  2. It reads +5 when high.
    But be aware that most atmels can sink more current than they can
    source.
     
  3. Rich Webb

    Rich Webb Guest

    It will be a "logic 1" but the guaranteed minimum voltage is 4.2 V.
    Check the datasheets; there is some variation among the AVR family in
    this parameter. Even with pull-ups, the actual value may be less than
    5.00 V if you're sourcing current.
     
  4. On the 8051 equivalents (89C52, etc.) one port is open collector, so
    requires an external pull-up, if I recall correctly.

    Read The Fascinating Manual for the particular microcontroller you are
    using to be sure....


    --
    Peter Bennett, VE7CEI
    peterbb4 (at) interchange.ubc.ca
    new newsgroup users info : http://vancouver-webpages.com/nnq
    GPS and NMEA info: http://vancouver-webpages.com/peter
    Vancouver Power Squadron: http://vancouver.powersquadron.ca
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-