ATmega325P datasheet(259/364 Pages) ATMEL

259 / 364 page

259

8023F–AVR–07/09

ATmega325P/3250P

Figure 24-2. Memory Sections

Note:

1. The parameters in the figure above are given in Table 24-6 on page 268.

24.5

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 24-2 and Table 24-3 for further details. The Boot Lock bits 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 pro-

gramming of the Flash memory by SPM instruction. Similarly, the general Read/Write Lock

(Lock Bit mode 1) does not control reading nor writing by LPM/SPM, if it is attempted.

0x0000

Flashend

Program Memory

BOOTSZ = '11'

Application Flash Section

Boot Loader Flash Section

Flashend

Program Memory

BOOTSZ = '10'

0x0000

Program Memory

BOOTSZ = '01'

Program Memory

BOOTSZ = '00'

Application Flash Section

Boot Loader Flash Section

0x0000

Flashend

Application Flash Section

Flashend

End RWW

Start NRWW

Application Flash Section

Boot Loader Flash Section

End RWW

Start NRWW

End RWW

Start NRWW

0x0000

End RWW, End Application

Start NRWW, Start Boot Loader

Application Flash Section

End Application

Start Boot Loader

End Application

Start Boot Loader

End Application

Start Boot Loader

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