Problem with PIC 16F819

[newbee]

Hello again: Here is an update on this strange chip. I placed the 1000 uF Capacitor on the input side of the 5V regulator as it was not letting the ICSP and placed 0.1 uf ceramic directly on the VSS & VDD pins. It still didn't work at 5 V, I gave it jolt by shorting VDD to ground momentarily, Lo and behold it started to work! ( previously I had 10 uf between VSS and VDD and 0.1 uf on both sides of the 5V regulator and one 0.1uf ceramic directly on VDD and VSS, I had even tried to power it with 9 V battery cells, so dont think anything was wrong with my previous circuit as 16F84A and 16F628A worked fine with that arrangement)

So now I must give it a jolt every time at start up to make it run. I have uploaded another program that uses LCD and PORTA.3 & PORTA.4 as input switches, this program also works. Next I will try to add small capacitance to OSC/RA6 and see if its external oscillator stabilizes.

[mackrackit]

Sounds like you are getting a handle on it and know what to look for.

BTW... Are you using Proton? Your code does not look like PicBasic.

[newbee]

Mack: Yes i am using Proton, haven't done any change in the circuit yet but seems I might be able to run it on external oscillator by adjusting capacitors on OSC1 & OSC2 ports. Just realized that the Microchip data sheet says 15 pf on each but I have 22 pf, this maybe the problem but why doesn't it run on internal RC, this has to be figured out.

[mackrackit]

You will probably have better luck on the Proton forum.

Here is how I would do it with Pic Basic Pro.

    DEFINE OSC 4           
    OSCCON = %01100000
    @ __config _CONFIG1, _INTRC_IO & _WDT_OFF & _LVP_OFF & _MCLR_OFF &_CP_OFF

[Acetronics2]

Hi, Newbee

Just open your PIC datasheet @ the OSC section, and you will discover the reset pin need a fast rising signal to act correctly ...
you also will find correct circuitry to pass by your supply lazyness ...

in other words, your supply is a bit slow when giving power, and the reset pin must be kept low till the supply voltage is established ...

that's why power supervisors like MC33064P / TC54 VN xx have been created.

Alain

[newbee]

Acetronics thanks, I tried both things grounding the MCLRE pin while powering it up with battery instead of adopter supply. It didn't work, so I think the chip must be faulty. Whether on external oscillator or internal its behavior doesn't change.

[aratti]

(From post 4) .....I had even tried to power it with 9 V battery cells

(From post 9)....so I think the chip must be faulty. Whether on external oscillator or internal its behavior doesn't change.

What did you expect after the 9 volts test ?


Al.