ATmega325P datasheet(268/364 Pages) ATMEL

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268

8023F–AVR–07/09

ATmega325P/3250P

24.8.13

ATmega325P/3250P Boot Loader Parameters

In Table 24-6 through Table 24-8, the parameters used in the description of the Self-Programming are given.

Note:

1. The different BOOTSZ Fuse configurations are shown in Figure 24-2

Note:

1. For details about these two section, see ”NRWW – No Read-While-Write Section” on page 257 and ”RWW – Read-While-

Write Section” on page 257.

Note:

1. Z0: should be zero for all SPM commands, byte select for the LPM instruction. See ”Addressing the Flash During Self-Pro-

gramming” on page 261 for details about the use of Z-pointer during Self-Programming.

Table 24-6.

Boot Size Configuration

(1)

BOOTSZ1

BOOTSZ0

Boot Size

Pages

Application

Flash Section

Boot Loader

Flash Section

End

Application

Section

Boot Reset

Address

(Start

Boot Loader

Section)

256 words

0x0000-0x3EFF

0x3F00-0x3FFF

0x3EFF

0x3F00

512 words

0x0000-0x3DFF

0x3E00-0x3FFF

0x3DFF

0x3E00

1024/ words

0x0000-0x3BFF

0x3C00-0x3FFF

0x3BFF

0x3C00

2048 words

0x0000-0x37FF

0x3800-0x3FFF

0x37FF

0x3800

Table 24-7.

Read-While-Write Limit

(1)

Section

Pages

Address

Read-While-Write section (RWW)

224

0x0000 - 0x37FF

No Read-While-Write section (NRWW)

0x3800 - 0x3FFF

Table 24-8.

Explanation of different variables used in Figure 24-3 and the mapping to the Z-pointer

(1)

Variable

Corresponding

Z-value

Description

PCMSB

Most significant bit in the Program Counter. (Program Counter is 14 bits

PC[13:0])

PAGEMSB

Most significant bit which is used to address the words within one page

(64 words in a page requires six/seven bits PC [5:0]).

ZPCMSB

Z14

Bit in Z-register that is mapped to PCMSB. Because Z0 is not used, the

ZPCMSB equals PCMSB + 1.

ZPAGEMSB

Bit in Z-register that is mapped to PCMSB. Because Z0 is not used, the

ZPAGEMSB equals PAGEMSB + 1.

PCPAGE

PC[13:6]

Z14:Z7

Program Counter page address: Page select, for Page Erase and Page

Write

PCWORD

PC[5:0]

Z6:Z1

Program Counter word address: Word select, for filling temporary buffer

(must be zero during Page Write operation)

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