Using weak pull-up

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  1. - 11th September 2007, 07:44 #7
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    Quote Originally Posted by dougsego View Post
    I'm attempting to configure portb.0 and portb.1 on a 16F883 as inputs with weak pull-ups. The register set-up code I'm using is:

    ANSELH=%00000000 'portb are all digital
    trisb=%00000011 ' portb.0 and portb.1 are inputs
    option_reg=%10010111 'Global Pull-up disabled and internal clk
    WPUB=%00000011 'Weak pull-up portb.0 and portb.1
    portb=%00000011 ' Outputs off, inputs don't care

    However, when I measure these nodes with a DVM (input impedance ~ or > 500K), I get 0v instead of the 5v I'm expecting.

    Any ideas?

    Thanks
    Hi Dougsego,
    Global pull up cleared means bit 7 should be set to zero: option_reg=%00010111 , see page 77 of the Data sheet:
    " 0 = PortB pullups are enabled by individual port LATCH values " .
    Last edited by Archangel; - 11th September 2007 at 07:48.
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