Problem with 12F675

stewc · Guest

Hi

I am having a power-on problem with a project I am doing using a PIC 12F675. The program is fairly simple - it just flashes an LED.

When I power-up (apply +5v) to the PIC, sometimes it works, sometimes not. I have tried all sorts of things to fix this but I am stuck - I havent seen this with another pic device and my hardware is ok.

The configuration fuses I have are

Internal RC no clk
WDT OFF
Power-up timer OFF (tried with ON and didnt work at all)
MCR Internal
BOD OFF
Code protect OFF
EE2 protect off.

I think it must be a reset issue but I dont know how to fix it. Any help would be great

TIA Stew

Guest · Posted: Thu Jun 26, 2008 5:25 am

This is what I use for my 12F683 projects...

#include <12f683.h>
#fuses INTRC_IO,NOWDT,NOPUT,NOPROTECT,NOMCLR

...perhaps you need to add the NOMLCR option ?

Jay

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Always post your compiler version. Some early versions of the compiler
have bugs in the init code for the comparator and/or ADC. If you post
your version, I can check if your version is affected.

andervsq · Joined: 17 Sep 2008 Posts: 1

Hi,

I'm having the same problem too. My CCS C is:
IDE version 3.36
PCB, PCM e PCW version 3.168

Is possible to write an ASM code to solve it?

Can you help me about it?

Thanks.

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Post your program that flashes an LED.

The program must be complete. It must have the #include, #fuses,
and #use delay statements, and a main(). It must compile with no errors.

drdelphi · Joined: 22 Apr 2007 Posts: 22 Location: Romania

you can try to enable both PUT (power up timer) and BOR (brown out reset).
putting a 100nF decoupling capacitor between VDD and VSS also might help.

good luck

kjrudko · Joined: 10 Feb 2009 Posts: 1

The 12F675 and 12F629 are one of the PICs that has a reset latching problem. The power supply must be very clean for it to run right. If you use a 5V regulator, the problem usually goes away, but if you are hooking up 5V directly, then transient voltages on the ms scale can cause the chip to lock up. The best fix is to use a decoupling capacitor with a voltage regulator or a small value resistor in series with the power supply.