16f864a
Thank you for all your advice.
I have partial success in programming the PIC. The PIC i am currently using is the PIC16F874 (without A)
I have tried to write to it, and only successfull for the first 26 bytes.
The write status is still failed. But the Read status is good. I managed to read whatevery contents in the PIC. I have also tried writing all 0xAA to the PIC but only part of them are programmed as 0xAA, the rest is 0x0A. Usually the odd ones are correct while the even ones are partial correct.
I am wondering does it have anything to do with Windows XP?
Also, based on the circuit, the serial data interface pin 4 are constantly negative. I remove this from the external power circuitry, so that it doesn't interferes, but I cannot disconnect it from controlling RB7. I believe this is the error that causes these writing problem since it is controlling the RB7.
Anyone can lend a helping hand? I uses an external 15V and 7805 to generate the 5V. So far, the 5V, the MCLR signal are fine.
Thanks!