Help with 16f628a

Plz help..
i used mplab(for hex file)+ic_prog+multi-pic programmer(serial port prog;from hamradioindia.com) for programming 16f628a..
i programmed it some 30 times or so.worked fine..but now when i try to do so,it can neither read the program inside the pic(shows blank) nor can i program it(verify error).but the program inside the pic works fine when connected to a circuit(led flashes).i tried using winpic too. it says 'Vdd select failed'.also i cannot program.can anyone help me please?

Code Protection

I hope that you have not selected to protect the code. This ( i think ) will prevent reprogramming the chip once again.

if possible and for fast check try to program another chip to see whither the problem with the chip or the programmer

i dont remember if i had turned code protection ON. so what if i had? can i turn it OFF? its been just two weeks since i bought it.i don wanna throw it away..

asp1987 said:

i dont remember if i had turned code protection ON. so what if i had? can i turn it OFF? its been just two weeks since i bought it.i don wanna throw it away..

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It doesn't matter if you have or not, as erasing the chip (or reprogramming it, which erases it first) first wipes the chip, then removes the code protection.

However, you probably shouldn't be setting code protection anyway!.

Hey Nigel, can u tell me if theres any way to say 4 sure that one PIC is damaged
or not? I want to know if mine is damaged.The program inside it works fine. i erased n programmed it;but of no use. verification error.

Only way really is to try another PIC, and see if that works. However, it's VERY difficult to damage a PIC, they are very sturdy devices. It might be that your programmer isn't erasing properly?, if Vpp is a little on the low side you might have problems.