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'[PIC]: Re: 16C84 RA1 depends on RA2 ?'
2000\08\26@090947 by Thomas Krampe

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Greg Maki wrote:

>
> Thomas,
>
> You may be running into the old read-modify-write problem when doing
> sucessive operations on an I/O port. You may want to look in the data
> book for a paragraph entitled "Sucessive Operations on I/O Ports" to get
> the details. Basically, you need to seperate I/O operations with some
> instructions to allow the port pins to stabilize before performing
> another operation on them.

Hi Greg and everyone else,

thank you for your answer, but this solved not my problem.

here is a short progam showing my problem:

But why is not going RA1 to the high level ?

       list p=16C84
port    equ 0x05

start   movlw   0x10
       tris    port
       movlw   0x00
       option
       nop
       nop
       nop
       nop
       nop
       nop
       nop
       nop
m_loop  movlw   0x03 ; Ra0 goes to high but Ra1 is staying low, Why ?
       movwf   port
       nop
       nop
       nop
       nop
       nop
       nop
       nop
       nop
       goto    m_loop

       end;

--
Thomas

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2000\08\26@130759 by Olin Lathrop

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>         list p=16C84
> port    equ 0x05

This is bad programming practise.  It may have nothing to do with the
problem at hand, but is another problem just waiting to happen.  You should
use the official include file that, among other things, defines the
addresses of each port register.  If you want to have you own PORT symbol,
the equate it to one of the supplied port symbols, not to a hard coded
value.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, spam_OUTolinTakeThisOuTspamcognivis.com, http://www.cognivis.com

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2000\08\26@151423 by Heinz Czychun

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Hi Thomas,

       Your program executes fine, the only thing I changed was the
processor type since I'm using an 'F84.

       I connected an LED through a 560 ohm resistor on each of port A
pin0, and pin 1 to verify operation.

       Are you connecting anything to the PIC?

       Could an external load be keeping RA1 from going high?

Heinz


At 3:01 PM 8/25/2000, Thomas Krampe wrote:
....<snip>...
{Quote hidden}

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2000\08\26@172854 by Thomas McGahee

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Looks like a hardware problem to me.

Disconnect any load on RA1 and observe the pin using
an oscilloscope.

If you are using an LED as the display element, is it
connected in the correct direction? Is the series
resistor the correct value? (measure it with a meter)
Try something between 330 ohms and 1k ohm for starters.
Is the LED defective? try exchanging LEDs between RA0 and RA1.
You should have one side of the LED connected to ground.

You might have a short between RA1 and an adjacent pin
or component. You can check that with an ohmmeter while
the circuit is turned off.

Fr. Tom McGahee

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2000\08\27@174629 by Tony Nixon
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Thomas Krampe wrote:

{Quote hidden}

Is the WDT enabled? If so, it will be resetting the chip every 18mS or
so.


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Best regards

Tony

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2000\08\27@230743 by Sandy Phelps

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You may have a bad 16C84. Sometimes it's the last thing you would think of.
Regards,
Sandy Phelps
----- Original Message -----
From: "Tony Nixon" <Tony.NixonspamKILLspamENG.MONASH.EDU.AU>
To: <.....PICLISTKILLspamspam.....MITVMA.MIT.EDU>
Sent: Sunday, August 27, 2000 2:45 PM
Subject: Re: [PIC]: Re: 16C84 RA1 depends on RA2 ?


{Quote hidden}

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2000\08\28@165001 by Thomas Krampe

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Hi,

i can only say tankyou to all, who tried to help me.

Finally it works as it should. I checked , rechecked my little circuit and
soldering it again. So i can clearly say it was my error. (shame on me)

--
Thomas

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