>>
I've been working with PIC16F87X , 4Mhz xtal and using A/D conversion.

My A/D result is perfectly only when I use internal RC oscillator.

MOVLW B'11000001'
MOVWF ADCON0        ;Chanel 0, Frc oscillator.

I've seen the most app, using Fosc/32 or Fosc/8.
If I set this, my A/D result became crasy.
have I done something wrong?
<<

The Tad period must be at least 1.6uS, which is exactly what you get with
Fosc/32 and a 20MHz oscillator.  In your case you should be able to use
Fosc/8, which comes out to 2.0uS with your 4MHz crystal.  Therefore 3 of the
4 Tad setting should work for you:

  01  Fosc/8
  10  Fosc/32
  11  internal RC oscillator

I can't say why only the internal RC appears to work.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, olin@embedinc.com, http://www.embedinc.com

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