Datasheet

353
ATmega16U4/32U4 [DATASHEET]
Atmel-7766J-USB-ATmega16U4/32U4-Datasheet_04/2016
28. Memory Programming
28.1 Program And Data Memory Lock Bits
The device provides six Lock bits which can be left unprogrammed (“1”) or can be programmed (“0”) to obtain
the additional features listed in Table 28-2. The Lock bits can only be erased to “1” with the Chip Erase
command.
Note: 1. “1”: unprogrammed, “0”: programmed
Table 28-1. Lock Bit Byte
()
Lock Bit Byte Bit No Description Default Value
ATmega16U4/32U4 ATmega16U4RC/32U4RC
7 – 1
6 – 1
BLB12 5 Boot Lock bit 1
BLB11 4 Boot Lock bit 0 1
BLB02 3 Boot Lock bit 1
BLB01 2 Boot Lock bit 1
LB2 1 Lock bit 0 1
LB1 0 Lock bit 0 1
Table 28-2. Lock Bit Protection Modes
(1)(2)
Memory Lock Bits Protection Type
LB Mode LB2 LB1
1 1 1 No memory lock features enabled.
2 1 0
Further programming of the Flash and EEPROM is disabled in
Parallel and Serial Programming mode. The Fuse bits are locked in
both Serial and Parallel Programming mode.
(1)
3 0 0
Further programming and verification of the Flash and EEPROM is
disabled in Parallel and Serial Programming mode. The Boot Lock
bits and Fuse bits are locked in both Serial and Parallel
Programming mode.
(1)
BLB0 Mode BLB02 BLB01
1 1 1
No restrictions for SPM or (E)LPM accessing the Application
section.
2 1 0 SPM is not allowed to write to the Application section.
3 0 0
SPM is not allowed to write to the Application section, and (E)LPM
executing from the Boot Loader section is not allowed to read from
the Application section. If Interrupt Vectors are placed in the Boot
Loader section, interrupts are disabled while executing from the
Application section.