ATMEGA8_14 Datasheet, PDF (204/331 Pages) ATMEL Corporation – High-performance, Low-power Atmel

Figure 102. Memory Sections⁽¹⁾
Program Memory
BOOTSZ = '11'
$0000
Application Flash Section
ATmega8(L)
Program Memory
BOOTSZ = '10'
$0000
Application Flash Section
Application Flash Section
Boot Loader Flash Section
Program Memory
BOOTSZ = '01'
End RWW
Start NRWW
End Application
Start Boot Loader
Flashend
$0000
Application Flash Section
Application Flash Section
Boot Loader Flash Section
Program Memory
BOOTSZ = '00'
End RWW
Start NRWW
End Application
Start Boot Loader
Flashend
$0000
Application flash Section
Application Flash Section
Boot Loader Flash Section
End RWW
Start NRWW
End Application
Start Boot Loader
Flashend
End RWW, End Application
Start NRWW, Start Boot Loader
Boot Loader Flash Section
Flashend
Note: 1. The parameters in the figure are given in Table 82 on page 213
Boot Loader Lock
Bits
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 78 on page 205 and Table 79 on page 205 for further details. The Boot 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 program-
ming of the Flash memory 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.
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