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PICList Thread
'Flickering output PortA'
1999\02\20@225806 by

picon face
Hi everybody, I need your help one more time.

I am using PIC 16F84 PortA as an output and sending a nibble (0001 - 1111)
everytime an output signal is required. The program works fine but the
circuit is not giving  a clean output. Some bits that should remain Low are
flickering once instead (47.2ms pulse  ).
I have noticed that it  happens in the closest bit to the activated output
bit. The  bit which flickes is different  according to the output nibble but
is always adjacent to an  activated (Hi)output bit.

Everything looks perfect when is simulated on MPLAB

Any help will be greatly appreciated.


Best wishes
                Eduardo R

AC Power Control project based on PIC
http://www.geocities.com/SouthBeach/Cove/4535
ICQ# 10909825
spam_OUTeriveraTakeThisOuTspamumemphis.campus.mci.net

        CHILDHOOD CANCER
"Anyone whose family hasn't been touched by it
should get down on his knees every night and
thank the MAN upstairs"...........SAM COOPER

1999\02\23@005646 by Roy Kasmir

picon face
Make sure that the reset pin is not floating.



---"Gerhard Fiedler (by way of \"Eduardo R.\"
<.....eriveraKILLspamspam@spam@umemphis.campuscwix.net>)" <listsspamKILLspamHOME.COM> wrote:
>
>  Hi everybody, I need your help one more time.
>
>  I am using PIC 16F84 PortA as an output and sending a nibble (0001
- 1111)
> everytime an output signal is required. The program works fine but the
> circuit is not giving  a clean output. Some bits that should remain
Low are
> flickering once instead (47.2ms pulse  ).
>  I have noticed that it  happens in the closest bit to the activated
output
> bit. The  bit which flickes is different  according to the output
nibble but
{Quote hidden}

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1999\02\23@123512 by Eduardo R.

flavicon
face
>Make sure that the reset pin is not floating.

Thank you for your reply.

Well I checked reset again and there is not problem with the that pin.

The problem is when I  send a nibble (0001-1111) to  PortA too many times
but the same each time , checking with the scope, I notice that the very
first nibble output is right but the following are  different, for example,
when I  try to send 0010 many times to portA, the very first output on portA
is 0010, which is correct but the output following the very first one  is
0001 instead. This shift from 0010 (1st. output) to 0001(subsequent outputs)
is seen like a flickering at the beginning of output on portA.


{Quote hidden}

Best wishes
                Eduardo R

AC Power Control project based on PIC
http://www.geocities.com/SouthBeach/Cove/4535
ICQ# 10909825
KILLspameriveraKILLspamspamumemphis.campus.mci.net

        CHILDHOOD CANCER
"Anyone whose family hasn't been touched by it
should get down on his knees every night and
thank the MAN upstairs"...........SAM COOPER

1999\02\23@150829 by Marc

flavicon
face
> >>  I am using PIC 16F84 PortA as an output and sending a nibble (0001
> >- 1111)
> >> everytime an output signal is required. The program works fine but the
> >> circuit is not giving  a clean output. Some bits that should remain
> >Low are
> >> flickering once instead (47.2ms pulse  ).

Remember that one of the Port-A pins is open collector (RA4). This might
cause flickering on HIGH output. It's not exactly what you wrote you
observed, but I thought it should be mentioned to make sure your circuit
does not suffer from that.

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