On Thu, 11 Jun 1998, Lauri Pirttiaho wrote:

> Re Carlos':
> >I'm really new to the PIC Microcontrollers. Recently I bought a very good
> >Beginner level programmer from ITUTECH and i tried to make my first assembly.
 I
> >built a card of prototypes but I could not find the crystal recommended for t
he
> >PIC. I use another vendors 4MHz, 1.5832MHz and 5MHz with 22 and 33 pf
> >condensators but nothing happen. The pic not work. The circuit is well conect
ed.
> >No mistakes. The chip pass the verify, programming and read test but later, i
n
> >the card, nothing happen. Where  the error is?
>
> The first question is: "what should happen?"
>
> In these situations it is always helpful to know some details of the
> circuit design and the program. The problem may be anywhere.
>
> Now, first you should check that the oscillator begins running: in this
> an oscilloscope is an invaluable tool. If it does not run you have a
> lot of choices: crystals are bad (unlikely), you have stray capacitances
> (possible), your program sets the oscillator options incorrectly,
> you have wrong operating voltages etc.
>
> If the oscillator is ok then your program should be executing. Now
> the "nothing happens" is probably a software problem. If you e.g.
> judge the "nothing happens" from the i/o ports, i.e. you do not
> get any expected output, you should check that the port is
> programmed as an output (be extra careful with the register
> bank selection) and that you do not overload the outputs.
> Also, RA4 is open drain so it does not source anything.
> Possible reasons for the "nothing happening" are vast so
> in the case the trouble shooting beats you, you could probably
> post some more details.
>
> Happy PICking!
>
> -- Lauri
>
> ---
> <a href="http://www.ee.oulu.fi/~lapi/">For more info.</a>
>
>
Hi,
all is correct. Only an addendum: check the level on the /MCLR pin. It
should be Vdd. Vdd should be also Vdd <G>.
Imre