ATMEGA640 datasheet(320/436 Pages) MICROCHIP

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ATmega640/V-1280/V-1281/V-2560/V-2561/V [DATASHEET]

DS40002211A

29.6.14

ATmega640 Boot Loader Parameters

In Table 29-7 through Table 29-9 on page 320, the parameters used in the description of the Self-Programming are

given.

Note:

1. The different BOOTSZ Fuse configurations are shown in Figure 29-2 on page 312.

Note:

1. For details about these two section, see “NRWW – No Read-While-Write Section” on page 311 and “RWW – Read-

While-Write Section” on page 311.

Note:

1. Z0: should be zero for all SPM commands, byte select for the (E)LPM instruction.

2. See “Addressing the Flash During Self-Programming” on page 314 for details about the use of Z-pointer during

Self-Programming.

Table 29-7.

Boot Size Configuration, ATmega640(1)

512 words

0x0000 - 0x7DFF

0x7E00 - 0x7FFF

0x7DFF

0x7E00

1024 words

0x0000 - 0x7BFF

0x7C00 - 0x7FFF

0x7BFF

0x7C00

2048 words

0x0000 - 0x77FF

0x7800 - 0x7FFF

0x77FF

0x7800

4096 words

0x0000 - 0x6FFF

0x7000 - 0x7FFF

0x6FFF

0x7000

Table 29-8.

Read-While-Write Limit, ATmega640

Section(1)

Pages

Address

Read-While-Write section (RWW)

224

0x0000 - 0x6FFF

No Read-While-Write section (NRWW)

0x7000 - 0x7FFF

Table 29-9.

Explanation of different variables used in Figure 29-3 on page 314 and the mapping to the Z-pointer,

ATmega640

Variable

Corresponding

Z-value(2)

Description(1)

PCMSB

Most significant bit in the Program Counter. (The Program Counter is 15

bits PC[14:0]).

PAGEMSB

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

(128 words in a page requires seven bits PC [6:0]).

ZPCMSB

Z15

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

ZPCMSB equals PCMSB + 1.

ZPAGEMSB

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

ZPAGEMSB equals PAGEMSB + 1.

PCPAGE

PC[14:7]

Z15:Z8

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

Write.

PCWORD

PC[6:0]

Z7:Z1

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

(must be zero during Page Write operation).

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