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Pic 16F876, output RA4 not working?

 
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elburro1887



Joined: 14 Feb 2006
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Pic 16F876, output RA4 not working?
PostPosted: Mon Feb 20, 2006 3:01 pm     Reply with quote
i am currently starting to program pics, so i wanted to test the output of the pins RA0 - RA5 with LEDs, but somehow the the pin RA4 isnt outputting anything, and i dont think i fried the pic
PCM programmer



Joined: 06 Sep 2003
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PostPosted: Mon Feb 20, 2006 3:19 pm     Reply with quote
Look in a PIC faq. See answer #85 in this one
http://home.netcom.com/~fastfwd/answers.html
newguy



Joined: 24 Jun 2004
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PostPosted: Mon Feb 20, 2006 3:19 pm     Reply with quote
Pin A4 on many PICs is not a normal I/O pin. It is usually an open drain output. You need an external pullup resistor in order to force that output high.
elburro1887



Joined: 14 Feb 2006
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PostPosted: Mon Feb 20, 2006 3:58 pm     Reply with quote
so there is no other method to output a high state on that pin?
fuzzy



Joined: 26 Feb 2005
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PostPosted: Mon Feb 20, 2006 4:14 pm     Reply with quote
No thre aren't other methods. you need to pullup that pin.
PCM programmer



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PostPosted: Mon Feb 20, 2006 4:27 pm     Reply with quote
More FAQs:

See item #3:
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1419&param=en001017

In this one, note that PICs typically have a limit of +8.5v on the pull-up
voltage:
http://www.acroname.com/robotics/info/concepts/opn_clct.html

http://www.mcc-us.com/Open-collectorFAQ.htm
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