I know this is very long, but please do read.

I'm using P89V51RD2 for a line follower robot. I chose it because it has in built PWM.

It works fine... But when I want to change the code, I use FlashMagic to flash the hex file. ISP works for some number of attempts. After few hours of continuous use (user Code/ISP), ISP starts failing. If I turn off the power for several hours and retry, it works..!

I tried changing 5 microcontrollers. I've also tried changing the capacitors in MAX232.

One more info:
My LFR sends sensor's to computer @ 9600 (for me to examine the sensors easily).
I'm able to see it very clearly in Hyperterminal, but ISP at same baud rate not working :((

It asks for "Reset the device into ISP Mode now", I reset it and then I get "Unable to communicate. Try reducing or increasing the baud rate".
But when this error occurs, I try resetting a microcontroller, open hyperterminal, send a text file that contains 4000 'U's, immediately removing the reset. And i get a bunch of 'U's in return.

All things working fine... But FlashMagic fails to flash the code.

I'm facing this problem for past 2-3 weeks...!


Again:
>> Tried 5 Microcontrollers :(
>> It works for few hours then fails
>> Tried both 1uF and 10uF capacitors
>> Though flashmagic fails, I'm able to receive 'U's and my program is also succussfull in communicating about the sensors.

The circuit I use to flash the hex file:
>> Rx/Tx to P89V51RD2 through MAX232 (using 1.0uF capacitors, also have another circuit with 10uF).
>> Pin 18/19 to 11.0592 crystal oscillator, and each to ground through 33pF capacitors.
>> pin 20 to ground, pin 40, EA to 5V
>> Vcc-----> Switch ----> To Pin 9 and Resistor -----> Ground.

I don't understand whats wrong with FlashMagic. Is there any alternative to it??

I tried checking all possible places where there could be a fault. But the bug still exists :((