STANGE PROBLEM WITH MY MCU

John Mayer · Guest

HOW IS THIS POSSIBLE and what im doing wrong??
Im using the 16F877 and ICD2 & mplab 7.11

I have programmed the target with "power od target" option.

After succesfully programming i pull out the ICD and i tested the program...All is working OK.

I pull out the baterry and i connect the battery again and program is started OK again.

I repeat this process 3 more times.

After the 4 time i connect the battery again and the program wont start.
Infact, there is no response but the power on target is still OK (3V).

WHY ?

DragonPIC · Joined: 11 Nov 2003 Posts: 118

Why Georgia why?

4th time consistently?

Will it work after a hard reset?
_________________
-Matt

Ttelmah · Guest

What clock rate?.
Have you measured the voltage at the unit, during programming, and on the first, second, third attempt.
Obvious thought would be that the supply voltage is borderline for the oscillator to work, and is being elevated by the programmer connections, and then drooping with time. Doing it reliably on a 'count', is almost inexplicable.

Best Wishes

valemike · Guest

on each time, try discharging your battery-less circuit, e.g. by taking a wire and shorting your VDD rail to ground.

Then try putting your battery back in. I think you won't be able to reproduce this problem anymore.

If that's the case, then looks like your caps are holding charge.