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'[PIC]: 877 + portC'
2001\04\18@040456 by Aart

picon face
Hello,

if i use PortC of the 16F877 as a "normal" output do i need to add an extra pull up resistor?
(just like Ra.4 of the 16F84, this is also a ST-buffer )

Thanks,
Aart.

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2001\04\18@043031 by Bob Ammerman

picon face
>Hello,
>
>if i use PortC of the 16F877 as a "normal" output do i need to add an extra
>pull up resistor?
>(just like Ra.4 of the 16F84, this is also a ST-buffer )
>
>Thanks,
>Aart.

No, Ra.4 of the 16F84 is open drain. PortC of the F877 is not.

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

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2001\04\18@075754 by Olin Lathrop

face picon face
> if i use PortC of the 16F877 as a "normal" output do i need to add an
> extra pull > up resistor?  (just like Ra.4 of the 16F84, this is also
> a ST-buffer )

You could have easily found this answer in the data sheet if you had looked.
Page 33, section 3.3 "PORTC and the TRISC Register" clearly documents port C
as having totem pole outputs.  So no, you don't need a pullup resistor.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, spam_OUTolinTakeThisOuTspamembedinc.com, http://www.embedinc.com

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2001\04\18@084547 by Drew Vassallo

picon face
> >if i use PortC of the 16F877 as a "normal" output do i need to add an
>extra
> >pull up resistor?
> >(just like Ra.4 of the 16F84, this is also a ST-buffer )

I think you are confusing Schmitt Trigger with open-drain.  Open-drain pins
require a pull-up to function as you cannot drive them high from the PIC.

PORTC of the '877 has no open-drain pins, so you don't NEED pull-ups.  You
can still use them, though, if your application requires it (i.e., using an
SPST pushbutton for input, pulled high, or for I2C communication).

--Andrew
_________________________________________________________________
Get your FREE download of MSN Explorer at http://explorer.msn.com

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2001\04\18@112637 by Edson Brusque

face
flavicon
face
Hello Aart,

>if i use PortC of the 16F877 as a "normal" output do i need to add an extra
pull up >resistor?

   it's a "normal" output.

   Regards,

   Brusque

-----------------------------------
Edson Brusque
Research and Development
C.I.Tronics Lighting Designers Ltda
(47) 323-2685  /  (47) 9993-6453
Blumenau  -  SC  -  Brazil
http://www.citronics.com.br
-----------------------------------

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2001\04\18@113259 by Bob Blick

face
flavicon
face
>if i use PortC of the 16F877 as a "normal" output do i need to add an
extra pull up resistor?
>(just like Ra.4 of the 16F84, this is also a ST-buffer )

No resistor needed, portC has normal outputs.

One thing I noticed yesterday, when used as inputs, not all the inputs on
portC have the same thresholds. RC0 had 0/1 thresholds of 1.8 and 2.65
volts. RC4 had thresholds of 2.1 and 2.5 volts. PIC was being supplied 5
volts.

Cheers,

Bob

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2001\04\18@180613 by Aart

picon face
Thank you all for the replies, yes i read the datasheet carefully still
didn't know for sure. Since i'm designing the pcb i'd rather be a 100% sure.
Thx !!
Aart.

> > if i use PortC of the 16F877 as a "normal" output do i need to add an
> > extra pull > up resistor?  (just like Ra.4 of the 16F84, this is also
> > a ST-buffer )
>
> You could have easily found this answer in the data sheet if you had
looked.
> Page 33, section 3.3 "PORTC and the TRISC Register" clearly documents port
C
> as having totem pole outputs.  So no, you don't need a pullup resistor.
>
>
i get tired to scroll down every message so i prefer to anwser on top..

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