I have solved my problem with 1K pull-down.  Many thanks to Pic Dude and
Fancisco.

Yansong


----- Original Message -----
From: Pic Dude <picdude@PILOTTOOLS.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Monday, August 26, 2002 7:01 AM
Subject: Re: keypad


> Not familiar with the TI chip.  However, where is the
> switch in your circuit drawing below?  You should be
> using one of these...
>
>           +Vcc
>             |         switch
>             R           |
>             |         --'--
> port -------o---------o   o---.
>                               |
>                               |
>                              Gnd
>
>
> OR...
>
>
>                    switch    +Vcc
>                      |        |
>                    --'--      |
> port -------o------o   o------'
>             |
>             R
>             |
>            Gnd
>
>
>
> > -----Original Message-----
> > From: pic microcontroller discussion list
> > [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of guy
> > Sent: Monday, August 26, 2002 10:50 AM
> > To: PICLIST@MITVMA.MIT.EDU
> > Subject: Re: keypad
> >
> >
> > Thanks for the feed back.  I did left the input floating.  The
> > chip is port6
> > of a TI msp430F413.  It doesn't has built-in pull-ups.  Is it right for
a
> > pull-down to be implemented as the following:
> >
> >
> > port---------|-----[Resistor]------ground
> >              |
> >              |
> >              input
> >
> > yansong
>
> --
> http://www.piclist.com hint: The list server can filter out subtopics
> (like ads or off topics) for you. See http://www.piclist.com/#topics
>
>

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics