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Which ATMEGA128 LockBits locks the chip forever and disables programming?

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sunsina

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Hi,

I Have bought a AVR Programmer and i had programmed ATMEGA128 AI.
I Had Programmed it . But Now I am not able to reprogram it.

Does it means that i have Accidently Locked the MCU and i can't Program it futher more ?

if So,what i Suppose to Do ? Use a New one.

Which ATMEGA128 LockBits Locks the Chip for ever and disables Programming?

Thnx in Advance.
 

tobb

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AVR

you can erase the lock bit by erase chip methode. In your case i guest
1. You set wrong fusebit so make it not alow you to program with ISP methode so you need Pararell programming methode
2. You select a wrong fusebit on crystal selecttion may be you select it to use external clock system that not a crystal.
3. Something wrong with your programmer or your chip

Incase 1 you must reprogram it with pararell methode. In this case it will hard if you not have programmer ,may be better to change new one
Incase 2 you must find external clock device , you could use 555 go generate clock or use other micro and program just set and reset state of pin and connect it to your MEGA128 and run Program
Incase 3 Try program other AVR check your programmer and setting on computer
 

sunsina

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Re: Reprogram AVR

Hi,
Dear Tobb
I Didn't Understand Case 2.

And is there any Simple Work to Do to Only Erase the Chip (Simplify th Parallel Programmer for Only Erasing Purpose!) If yes,Plz Send me Schematic.
Thnx
 

tobb

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Reprogram AVR

in case 2 some people were chose wrong fusebit about clock source. The crystall need oscilator circuit inside avr to make clock. So if you chose any other than crystall then oscilator circuit will not work so you need to put clock source that can generate clock by it self and connect it to xtal pin of avr

i dont have any circuit for pararell programming mode so let's hope you didn't set programming wrong then.. I don't know if any body have other way or not..
 

mmohamed15

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Re: Reprogram AVR

if your programmer isn't have an external oscillator (crystal ) i think you may change that option in the mega128 , you must know that orginally all avr microcontrollers areshiped with the internal oscillator fuse bit programmerd if you changed that option you must use an exteranl oscillator for programming
 

Mazi3

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Re: Reprogram AVR

you probably missuse the bits for oscilator selection. try to drive the clockin (xtal1 or xtal2) with 5Vpp square wave from 100kHz to 1Mhz, to reprogram the fuses.
use series resistor of 1k...4k7. but you can still damage chip...

I've burned one that way :)

remember, the programmed means 0!!!!! and vice versa, soo if you need zero on some place, then you have to program that fuse bit (I'm using ponyprog...).
 

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