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bryan2
Visitor II
April 11, 2004
Question

Port pull ups??

  • April 11, 2004
  • 4 replies
  • 928 views
Posted on April 11, 2004 at 10:32

Port pull ups??

    This topic has been closed for replies.

    4 replies

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    danielh1
    Visitor II
    May 17, 2011
    Posted on May 17, 2011 at 11:59

    Good question. These ports have pull-up, see page 49 of the datasheet. At page 147 the input low current is specified to be at least -10uA and at most -50uA. That means the pull-value value is between 100K and 500K. Compare this to the standard 50K (typical) of a traditional 8051 machine. If you are designing a board and you need pull-ups on some input, you should better place external resistors and not rely too much on these internal pull-ups: the lower the resistance the greater will be RFI immunity (at the expense of more current).

    Daniel

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    bryan2Author
    Visitor II
    May 17, 2011
    Posted on May 17, 2011 at 11:59

    Hi,

    Are we reading the same data sheet(uPSD33xx, not 32xx)? Mine is Sep. 2003, it is only 129 pages. I can't find newer one on ST website.

    Bryan
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    bryan2Author
    Visitor II
    May 17, 2011
    Posted on May 17, 2011 at 11:59

    Hi,

    Do port1--4 of uPSD33xx have internal pull-ups? If yes, how many ohm? I can't find this kind of information in data sheet. Thanks.

    Regards

    Bryan
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    danielh1
    Visitor II
    May 17, 2011
    Posted on May 17, 2011 at 11:59

    Sorry, I was refering to uPSD32xx. I don't think that there is any difference for the port specifications.

    Daniel

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