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'Are ports RA4 and RA5 on 16C73 'Special' ?'
1999\04\21@075714 by Jim Dolson

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I'm obviously missing something here.  I am trying to use ports RA0
through RA5 as digital I/O lines instead of analog input lines.  RA0 -
RA3 work fine.  I would like to use RA4 and RA5 for digital output only,
but I can't seem to get them to work.

Can anyone give me a hint as to why RA4 and RA5 might be 'special' in
some way?  The problem with RA4 may be related to my use of the internal
counter/interrupt.  What about RA5?

Thanks.

Jim
spam_OUTjdolsonTakeThisOuTspamiserv.net

1999\04\21@080934 by Bart Stofferis

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Hi Jim,

the function of the PORTA pins can't be arbitrary choosen, I refer to
the databook pages (p.44 Table5.1)

There are 6 possible configurations which I summarize in the table
below:

RA0 RA1 RA2 RA3 RA4 RA5
A       A     A     A      X     A
A       A     A    ref      X     A
A       A     A     A      X     A
A       A     D     A      X     D
A       A     D    ref     X      D
D       D     D     D     X      D

where A is analog input, D is digital I/O and X is don't care
ref is external reference voltage
RA4 is an OPEN DRAIN type so you need an external pullup resistor to put
the line high.

you're welcome ...

Bart
ON6HF

> {Original Message removed}

1999\04\24@063744 by Dr. Imre Bartfai

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Hi,
RA4 is special for output as it is OPEN COLLECTOR rather than any other
output configured pins which are TOTEM POLE. This means it is not possible
to drive high by RA4. Maybe you should use a pullup resistor to do this.
I hope this helps.

Imre

P.S. It is a well-know RTFM fact, however, most people tends to forget it
(including me...)


On Wed, 21 Apr 1999, Jim Dolson wrote:

{Quote hidden}

1999\04\26@051750 by Benjamin Petersen

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part 0 464 bytes
Hi,
RA4 is special for output as it is OPEN COLLECTOR rather than any other
output configured pins which are TOTEM POLE. This means it is not possible
to drive high by RA4. Maybe you should use a pullup resistor to do this.
I hope this helps.

And to supply any current I think it would be vice to use a mosfet. (or at least a transistor only for SMALL currents as far as I remember, but then again I'm just a programmer)



Med venlig hilsen

Benjamin Petersen


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