[SOLVED] PIC16F877A not working even after bieng programmed successfully using ICPROG

[illegal121]

yes i think You are rite.. I use 10 ms delay during that 6 times high /low on port B , but LEDes are not blinking with the same delay as specified they are blinking with their wish..

 

[bigdogguru]

Is the LED blinking stable on RB1 or RB0?

Also you are using a current limiting resistor, correct? 300 - 400 Ohms.

BigDog

 

[illegal121]

No, LEDes are not stable.. :???:
Yes I am using resistors..

 

[bigdogguru]

Do you have any smaller capacitors, like 22pF?

If so switch out the 30pF for those.

BigDog

 

[illegal121]

yes.. i changes both crystal oscillator and capacitor but no use...:S

 

[bigdogguru]

What are you using as a power supply?

Do you have a slower crystal, 4MHz?

Also remove the programmer and see if the LED stablizes.

BigDog

 

[illegal121]

strange .. :S
I also try WinPIC it also verifies and programmed successfully ..

 

[bigdogguru]

I have no doubt you have programmed the device successfully.

Stability is the issue. Do you have the crystal and capacitors as close to the PIC as possible?

BigDog

 

[illegal121]

I am using FIXED 5V .. I tried 20Mhz and 11Mhz..

 

[bigdogguru]

I am using FIXED 5V ..

You mean a regulated 5V supply?

I tried 20Mhz and 11Mhz..

One other thing have you installed a 100nF capacitor across the Vdd and Vss pins (5v to GND), keeping it a close as possible to the PIC?

BigDog

 

[romel_emperado]

One other thing have you installed a 100nF capacitor across the Vdd and Vss pins (5v to GND), keeping it a close as possible to the PIC?

why it need to be close as possible while if we place it a little far then it's the same connection.?
I believe this trick also I have experienced about this and Im puzzled why it needs to be close.. hmmm

 

[illegal121]

Oh Sir thanks Alot for Your such a precious time... :-D
That was issue of supply .. I dont know why but i remove regulator and give direct 5V from supply it's working now.. :S

 

[bigdogguru]

Well in regards to the crystal any relatively high frequency signal path should be keep to a minimum.

Stray capacitance, EMI, etc all play a role in the ability to deliver a clean clock signal.

The capacitor across the Vdd and Vss absorbs any EMI or noise on the +5V and GND lines keeping it to a minimum.

Does this make sense?

BigDog

---------- Post added at 05:17 ---------- Previous post was at 05:16 ----------

Glad to hear it. Good clocks and power supplies are essential with almost any MCU.

 

[illegal121]

I dont know why.. As regulator was also giving 5 V ..

---------- Post added at 09:23 ---------- Previous post was at 09:19 ----------

Well thanks Romel and bigdogguru... ! Happy that You people are here to help beginners like us :razz:

 

[bigdogguru]

I would have to see the regulator circuit to be able to give an opinion.

It obviously was not providing a stable 5V supply, perhaps noise, etc.

Did you put that 100nF capacitor between 5V and GND as close as possible to the PIC?

BigDog

 

[illegal121]

Yes.. I did... But I think my supply still not giving stable voltages .. I should use regulator ..
I was using regulator 7805..

---------- Post added at 09:38 ---------- Previous post was at 09:30 ----------

hey guys my original program is also working...

---------- Post added at 11:28 ---------- Previous post was at 09:38 ----------

hello .. Again :smile:
my program shows output like this on virtual terminal (simulation)

this is due to line present in my code this is

UART1_Write(13);

but in real hype terminal it is overwriting the same first line continuously..

Any Help ...
thank you..

 

[bigdogguru]

but in real hype terminal it is overwriting the same first line continuously..

You can output a newline character (\n} after each successive line.

You can also add a delay in your program after each outputted line, this will slow down the display on hyperterminal.

BigDog