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Please help for initial reset problem

 
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andy_o
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Please help for initial reset problem
PostPosted: Sat Apr 08, 2006 11:46 am     Reply with quote
Dear all,
Have somebody ever encountered intial reset problem for pic microcontroller.
It happen 2 or 3 times for the first few seconds when I power on the pic. I do have 0.1 uf capacitor for Vcc to ground , 0.1uF and 220 UF for Voltage regulator. I have MCLR pin pull up to Vcc. Could somebody help me out how many possibilities that will cause the initial reset problem.

I appreciate all helps sir.

Andy O.
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Sat Apr 08, 2006 1:00 pm     Reply with quote
You didn't really tell us what your problem is. I assume that it must
be that the PIC resets a few times after you first turn the power on.

Try these things:

1. Disable the Watchdog Timer.

2. If your PIC supports Low Voltage Programming mode, disable it.

3. Enable Brownout reset.

4. Enable the Power-up timer.

5. Use the correct Oscillator fuse setting for your crystal frequency.

Example:

For a 20 MHz crystal:

Code:
#include <16F877.H>
#fuses  HS, NOWDT, BROWNOUT, PUT, NOLVP
#use delay(clock=20000000)



In hardware:

1. Check your power supply. Make sure it puts out the proper voltage
quickly, and does not go down to some lower voltage for a while.

2. Check your crystal oscillator circuit. Use the correct value of
capacitors for your crystal, according to the PIC data sheet.

3. Make sure you have a pull-up resistor on the MCLR pin. If you have
the Microchip ICD2, use a 10K pullup. For CCS ICD, use 47K.

4. Make sure all power and ground pins on your PIC are properly
connected.

5. Check the external circuits that are connected to your PIC, such as
LEDs, or transistors, or motors, etc. Make sure you are not trying
to use more current from any PIC pin than the rated amount,
according to the data sheet. (Usually 20 or 25 ma).
andy_o
Guest
big thanks
PostPosted: Sun Apr 09, 2006 1:02 pm     Reply with quote
Thank you sirs,
I will try all of your suggestions. I love this forum now.

I appreciate any helps sirs

Andy
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