ATmega325PA Atmel Corporation, ATmega325PA Datasheet - Page 270

• Manufacturer Part Number: ATmega325PA
• Manufacturer: Atmel Corporation

26.5
8285D–AVR–06/11
Boot Loader Lock Bits
ATmega165A/PA/325A/PA/3250A/PA/645A/P/6450A/P
If no Boot Loader capability is needed, the entire Flash is available for application code. The
Boot Loader has two separate sets of Boot Lock bits which can be set independently. This gives
the user a unique flexibility to select different levels of protection.
The user can select:
• To protect the entire Flash from a software update by the MCU.
• To protect only the Boot Loader Flash section from a software update by the MCU.
• To protect only the Application Flash section from a software update by the MCU.
• Allow software update in the entire Flash.
See
and general Lock bits can be set in software and in Serial or Parallel Programming mode, but
they can be cleared by a Chip Erase command only. The general Write Lock (Lock Bit mode 2)
does not control the programming of the Flash memory by SPM instruction. Similarly, the gen-
eral Read/Write Lock (Lock Bit mode 1) does not control reading nor writing by LPM/SPM, if it is
attempted.
Table 26-2.
Note:
Table 26-3.
Note:
BLB0 Mode
BLB1 Mode
Table 26-2 on page 270
1
2
3
4
1
2
3
4
1. “1” means unprogrammed, “0” means programmed
1. “1” means unprogrammed, “0” means programmed
Boot Lock Bit0 Protection Modes (Application Section)
Boot Lock Bit1 Protection Modes (Boot Loader Section)
BLB02
BLB12
1
1
0
0
1
1
0
0
BLB01
BLB11
and
1
0
0
1
1
0
0
1
Table 26-3 on page 270
Protection
No restrictions for SPM or LPM accessing the Application
section.
SPM is not allowed to write to the Application section.
SPM is not allowed to write to the Application section, and 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.
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.
Protection
No restrictions for SPM or LPM accessing the Boot Loader
section.
SPM is not allowed to write to the Boot Loader section.
SPM is not allowed to write to the Boot Loader section, and LPM
executing from the Application section is not allowed to read
from the Boot Loader section. If Interrupt Vectors are placed in
the Application section, interrupts are disabled while executing
from the Boot Loader section.
LPM executing from the Application section is not allowed to
read from the Boot Loader section. If Interrupt Vectors are
placed in the Application section, interrupts are disabled while
executing from the Boot Loader section.
for further details. The Boot Lock bits
(1)
(1)
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