Boot Loader Lock Bits; Memory Sections - Atmel ATmega128 Manual

Boot Loader Lock
Bits
2467S–AVR–07/09
Figure 133. Memory Sections
Program Memory
BOOTSZ = '11'
Application Flash Section
Application Flash Section
Boot Loader Flash Section
Program Memory
BOOTSZ = '01'
Application Flash Section
Application Flash Section
Boot Loader Flash Section
Note: 1. The parameters in the figure above are given in
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 Table 108 and Table 109
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 mem-
ory by SPM instruction. Similarly, the general Read/Write Lock (Lock bit mode 3) does not
control reading nor writing by LPM/SPM, if it is attempted.
(1)
Program Memory
$0000
Application Flash Section
End RWW
Start NRWW
Application Flash Section
End Application
Boot Loader Flash Section
Start Boot Loader
Flashend
Program Memory
$0000
Application flash Section
End RWW
Start NRWW
End Application
Boot Loader Flash Section
Start Boot Loader
Flashend
for further details. The Boot Lock bits can be set in software and in
ATmega128
BOOTSZ = '10'
$0000
End RWW
Start NRWW
End Application
Start Boot Loader
Flashend
BOOTSZ = '00'
$0000
End RWW, End Application
Start NRWW, Start Boot Loader
Flashend
Table on page 284.
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