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What is mean by 3 level program memory lock in 89s52?

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January 11, 2011 12:18PM

Program Memory Lock Bits

The AT89S52 has three lock bits that can be left unprogrammed

(U) or can be programmed (P) to obtain the additional

features listed in the following table.

Program Lock Bits

LB1 LB2 LB3 Protection Type

1 U U U No program lock features

2 P U U MOVC instructions executed

from external program

memory are disabled from

fetching code bytes from

internal memory, EA is

sampled and latched on reset,

and further programming of

the Flash memory is disabled

3 P P U Same as mode 2, but verify is

also disabled

4 P P P Same as mode 3, but external

execution is also disabled