PIC resets every now and then

My pic 16F73 resets every now and then.
I am using a 20MHz external crystal with 2 x 22 pf capacitors.
I also have a 10K resistor between between MCLR and +5V.
Even if I scale down my program to a few lines consisting only of output to the LCD, my pic still resets every now and then.
I have followed Darren Taylors advice and have sent the output of the
POR, BOR, TO and PD bits to the LCD just after initialization, as to help to determine what cause the resets.
The values after each reset is as follow:
POR=0 (Power-On reset PCON.1)
BOR=0 (Brown-out reset PCON.0)
TO=1 (Time-out bit STATUS.4)
PD=1 (Power-down bit STATUS.3)

Using the above values as a clue, what could be the problem?
Accortding to the datasheet, POR=0, BOR=unknown, TO=1, PD=1 indicates it was a Power-on-reset.
This doesnot make sense. How can a Power-on reset happen 10-30 seconds after startup?

All is in the title ...

just Thanks missing ...

Alain

AceTronics

My circuit looks exactly like the one on p.96 of the PBP manual that shows the default setup for connecting a LCD. (except for the fact that I am using a pic16f73 and a 20MHz crystal).

Thus default connections for LCD.

DEFINE OSC 20

DEFINE LCD_DREG PORTA
DEFINE LCD_DBIT 0
DEFINE LCD_RSREG PORTA
DEFINE LCD_RSBIT 4
DEFINE LCD_EREG PORTB
DEFINE LCD_EBIT 3

DEFINE LCD_BITS 4
DEFINE LCD_LINES 4
DEFINE LCD_COMMANDUS 2000
DEFINE LCD_DATAUS 50
DEFINE NO_CLRWDT 1 ' Don't insert CLRWDTs

TRISB=0 ' PORTB is output

ADCON1 =7 ' PORTA is digital


Thanking you in advance for any help or suggestions!

I would -

Add a 10uF tantalum cap very near the PIC between Vdd and GND. I would also lower the pull-up on MCLR to 4.7K.

Charles

The 10uF tantalum cap very near the PIC between Vdd and GND solved my problem!

Thanks so much!!