ATMEGA640 datasheet(321/436 Pages) MICROCHIP

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

DS40002211A

29.6.15

ATmega1280/1281 Boot Loader Parameters

In Table 29-10 and Table 29-11, 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.

Notes: 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.

3. The Z-register is only 16 bits wide. Bit 16 is located in the RAMPZ register in the I/O map.

Table 29-10. Boot Size Configuration, ATmega1280/1281(1)

512 words

0x0000 - 0xFDFF

0xFE00 - 0xFFFF

0xFDFF

0xFE00

1024 words

0x0000 - 0xFBFF

0xFC00 - 0xFFFF

0xFBFF

0xFC00

2048 words

0x0000 - 0xF7FF

0xF800 - 0xFFFF

0xF7FF

0xF800

4096 words

0x0000 - 0xEFFF

0xF000 - 0xFFFF

0xEFFF

0xF000

Table 29-11. Read-While-Write Limit, ATmega1280/1281

Section(1)

Pages

Address

Read-While-Write section (RWW)

480

0x0000 - 0xEFFF

No Read-While-Write section (NRWW)

0xF000 - 0xFFFF

Table 29-12. Explanation of different variables used in Figure 29-3 on page 314 and the mapping to the Z-pointer,

ATmega1280/1281

Variable

Corresponding

Z-value(2)

Description(1)

PCMSB

Most significant bit in the Program Counter. (The Program Counter is 16

bits PC[15:0])

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

Z16(3)

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[15:7]

Z16(3):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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