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'[PIC]: Newbie trying to get a 16f84_4 to work unsu'
2001\09\19@123741 by William Cox

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Hi, I'm new to the PIC world. I do robotics. I've got a programmer (Tait
style) from http://www.electronics123.com (P16PRO). I've got it working and I've
programmed a PIC with the JAL code on this page
(http://www.gorobotics.net/zac/ppu.shtml). I've also hooked it up according to the
schematic on the above page (5.5v MCLR pulled high, resister through LED to
GND, 24pF cap and 21k R/C oscillator) but it wont work (it's supposed to
blink a LED). I think the problem is my oscillator. I'm not sure what values
I should use. Right now I've modified the JAL library for the f84 to be in
XT mode with a 2mHz clock. I'm using a 24 pF cap and a 21k resistor. That
should give me ~2mHz right? I don't have a o-scope so I can see. Does anyone
have any hints? Is there a good tutorial about getting a simple LED to blink
on a x84 with a R/C clock? Thanks.
-William


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2001\09\19@125458 by Bob Barr

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William Cox wrote:
>
>Hi, I'm new to the PIC world. I do robotics. I've got a programmer (Tait
>style) from http://www.electronics123.com (P16PRO). I've got it working and I've
>programmed a PIC with the JAL code on this page
>(http://www.gorobotics.net/zac/ppu.shtml). I've also hooked it up according to the
>schematic on the above page (5.5v MCLR pulled high, resister through LED to
>GND, 24pF cap and 21k R/C oscillator) but it wont work (it's supposed to
>blink a LED). I think the problem is my oscillator. I'm not sure what
>values
>I should use. Right now I've modified the JAL library for the f84 to be in
>XT mode with a 2mHz clock. I'm using a 24 pF cap and a 21k resistor. That
>should give me ~2mHz right? I don't have a o-scope so I can see. Does
>anyone
>have any hints? Is there a good tutorial about getting a simple LED to
>blink
>on a x84 with a R/C clock? Thanks.
>-William
>

Your R and C values appear about right but your mode needs to be set to RC
mode, not XT mode. I'll check the frequency on a breadboard that I've got
and get back to you with the value I read.

Regards, Bob


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2001\09\19@131558 by Bob Barr

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Bob Barr <spam_OUTbob_barrTakeThisOuTspamHOTMAIL.COM>
{Quote hidden}

With a 22pf cap and a 22k resistor, I'm seeing about 280 KHz on CLKOUT.
That's an Fosc of 1.12 MHz. Since you're using 2 more pF of capacitance and
1 less K of resistance, you're probably pretty close to your 2 MHz clock.
YMMV.

Regards, Bob

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2001\09\19@141535 by uter van ooijen & floortje hanneman

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> >>I should use. Right now I've modified the JAL library for the f84 to be
in
> >>XT mode with a 2mHz clock. I'm using a 24 pF cap and a 21k resistor.
That
> >>should give me ~2mHz right? I don't have a o-scope so I can see. Does

I gather that you (want to) use the RC mode? In that case you must enable RC
instead of XT mode! If that can not be done in your programmer you can
crearte a 16F84_RC2.JAL file containing

>>>>
pragma target chip        16f84
pragma target clock       2_000_000
pragma target osc         rc
pragma target watchdog    off
pragma target powerup     on
pragma target protection  off
<<<<

Wouter van Ooijen

Van Ooijen Technische Informatica: http://www.voti.nl
Jal compiler for PIC uC's:  http://www.xs4all.nl/~wf/wouter/pic/jal

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'[PIC]: Newbie trying to get a 16f84_4 to work succ'
2001\09\19@150104 by William Cox

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Thanks Bob, the trick was changing the mode from XT to RC. Too bad JAL docs
don't have the modes listed :( Thanks a buch. This is so exciting. But, the
1 sec. pause now takes 2 seconds. That would mean I'm closer to 1 mHz than
2 - correct? Actually I'm using a 22k also. I'll play around with it and see
what I can do.
-William


===========================================
The GoRobotics Network - http://www.gorobotics.net
The Robot Directory - http://www.robotdirectory.org
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Are you 100% that if you died tonight you'd go to heaven?
Why have doubts? You don't want to be wrong.
===========================================
"Congress shall make no law respecting an establishment
of religion, or prohibiting the free exercise thereof; or
abridging the freedom of speech ... " - US Bill of Rights


{Original Message removed}

2001\09\19@155641 by Bob Barr

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William Cox wrote:
>
>Thanks Bob, the trick was changing the mode from XT to RC. Too bad JAL docs
>don't have the modes listed :( Thanks a buch. This is so exciting. But, the
>1 sec. pause now takes 2 seconds. That would mean I'm closer to 1 mHz than
>2 - correct? Actually I'm using a 22k also. I'll play around with it and
>see
>what I can do.

I believe wouter has posted the pragma need to select RC mode in JAL. (I'm
not familiar with JAL so I can't help on that one.)

I was mistaken on my previous post. The larger capacitance that you're using
would actually slow your clock to below the 1.2 MHz that I saw. Around a 1
MHz clock resulting from 24 pF with 22 K is quite reasonable.

Regards, Bob


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2001\09\19@173749 by Jinx

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> 1 sec. pause now takes 2 seconds. That would mean I'm
> closer to 1 mHz than 2 - correct? Actually I'm using a 22k
> also. I'll play around with it and see what I can do.
> -William

Hi William, this may help

http://home.clear.net.nz/pages/joecolquitt/0f84rc.html

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