at89c51re2-slsem ATMEL Corporation, at89c51re2-slsem Datasheet - Page 52

• Manufacturer Part Number: at89c51re2-slsem
• Description: At89c51re2 8-bit Flash Microcontroller
• Manufacturer: ATMEL Corporation

Flash Protection from Parallel Programming
52
AT89C51RE2
The three lock bits in Hardware Security Byte (see "In-System Programming" section)
are programmed according to Table 21 provide different level of protection for the on-
chip flash memory FM0.
They are set by default to level 4
Table 31. Program Lock Bit FLB2-0
Program Lock bits
U: unprogrammed
P: programmed
WARNING: Security level 2 and 3 should only be programmed after verification.
Security
level
1
2
3
4
Program Lock Bits
FLB0
U
P
U
U
FLB1
U
U
P
U
FLB2
U
U
U
P
Protection Description
No program lock features enabled.
MOVC instruction executed from external program memory are
disabled from fetching code bytes from internal memory, EA is sampled
and latched on reset, and further parallel programming of the Flash is
disabled.
ISP allows only flash verification (no write operations are allowed) but
IAP from internal code still allowed.
Same as 2, also verify through parallel programming interface is
disabled and ISP read operation not allowed.
Same as 3, also external execution is disabled (external bank not
accessible)
7663B–8051–03/07