ATMEGA8_08 Datasheet, PDF (211/308 Pages) ATMEL Corporation – 8-bit with 8K Bytes In-System Programmable Flash

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 220.
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 and Table 79 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 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.
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