PIC18F4431 won't start up

[jeanxxx]

Hi guys,

I'm currently using a PIC18F4431(I've used a PIC16F877A before).

My design is very simple, a 20MHz crystal with 2 15pF caps and 8 LEDs at PortB.

Vdd, AVdd and MCLR pins are pulled to 5V and Vss, AVss pins are pulled to ground.

I've written the software using ASM and programmed it using MPLAB ICD 2

I've set the __CONFIG 1H register such that the chip is operating in HS mode.

However, when I power up, the chip won't start at all. I tried to look at the signal at the OSC2/CLKO pin and I find that there isn't any clock pulse generated by the internal oscillator.

Later on, I tried to put a cap from Vdd to GND but still it refused to start up. :x

Can anyone give me any advice on how to solve this? Any feedback will be much appreciated. :sm27:

Thanks in advance.

Regards,
Jean

 

[XNOX_Rambo]

MCLR is active low so if you pull it to Vss (if that is what you are saying) then
you are applying a continuous reset.

/Rambo

 

[jeanxxx]

NO, the MCLR is pulled to 5V
i mean Vss and AVss are pulled to GND

thanks anyway RAMBO

Jean

 

[XNOX_Rambo]

Sorry, it was very late so I misread your sentence... :wink:

Anyway, the oscillator should be running even if the reset pin is active, so
the only other thing that comes to mind is that the PIC has found the SLEEP
command in your code - and gone to sleep.
Or then it it just might be broken.

Sorry, but that is all the advice I can give.

/Rambo

 

[checkmate]

Wrong configuration words may also cause the oscillator to fail to start up.

 

[ot001]

Dear jeanxxx,

did you manage to solve how to get the PIC184431 to start up? I have the same problem. Have tried in many different ways to get it to start up with ext RC osc or the int osc block. Have tried to set the config bits both in code and the MPLAB IDE table. Getting no reaction whatsoever from the PIC:s (have tried on 2 different). Can you perhaps give me some advice how to solve the startup?

Regards, OT

Why are you digging out 7 years old post? instead you can start a new thread MODERATOR ACTION: MODERATOR ACTION:

 

[sreepss]

did u enable the brown out reset????