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Author Topic: Question for AVR Lock Bit Fuse  (Read 2655 times)
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chyun3
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« on: February 19, 2008, 06:00:10 06:00 »

I read the datasheet of ATMEGA48 and still donot understand the function of the 3 modes of Lock Bit...It use to prevent other from read out the flash & eeprom ? Or it use to prevent other rewrite the flash & eeprom ? ..


Can ATMEGA48 code protect the Flash memory part while allow the eeprom data to be read out ?
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telyadi
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« Reply #1 on: February 19, 2008, 11:39:50 11:39 »

I usually release my chip with lockbit so no one can't read the flash. But if I need to update or bug fixed, I can erase that chip and write again.  With the lock bit set, my program can read and write value to the EEPROM. But someone can't read it via ISP programmer.
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Mega32
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« Reply #2 on: February 19, 2008, 08:05:31 20:05 »

@chyun3

The lockbits will not prevent anyone from doing a "Full Chip Erase" , and then reprogram the MCU.
They can prevent anyone from reading out the application in flash , without doing a "full erase"

As for reading out the eeprom , you can implement a readout function in your application.


/Mega32
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mpas
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« Reply #3 on: February 24, 2008, 01:04:15 13:04 »

LB1,LB2:
 1    1     no restrictions for read/write
 0    1     you can read/verify but write is not allowed; fuses are disabled
 1    0     not allowed bits combination
 0    0     read/verify and write is not allowed; fuses are disabled

erase chip is allowed already
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billy48
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« Reply #4 on: March 04, 2008, 05:24:59 05:24 »

Be careful about setting bit
otherwise the system will become unstable
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