ATmega32U2 datasheet(239/314 Pages) ATMEL

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239

7799B–AVR–07/09

ATmega8U2/16U2/32U2

23.8.14

ATmega8U2 Boot Loader Parameters

In Table 23-8 through Table 23-10, the parameters used in the description of the Self-Programming are given.

(Page size = 64 words = 128 bytes)

Note:

1. The different BOOTSZ Fuse configurations are shown in Figure 23-2.

Note:

1. For details about these two section, see “NRWW – No Read-While-Write Section” on page 227 and “RWW – Read-While-

Write Section” on page 227.

Note:

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

See “Addressing the Flash During Self-Programming” on page 232 for details about the use of Z-pointer during Self-

Programming.

Table 23-8.

Boot Size Configuration

(1)(Word Addresses)

256 words

0x0000 - 0xEFF

0xF00 - 0xFFF

0xEFF

0xF00

512 words

0x0000 - 0xDFF

0xE00 - 0xFFF

0xDFF

0xE00

1024 words

0x0000 - 0xBFF

0xC00 - 0xFFF

0xBFF

0xC00

2048 words

0x0000 - 0x7FF

0x800 - 0xFFF

0x7FF

0x800

Table 23-9.

Read-While-Write Limit

(1)

Section

Pages

Address

Read-While-Write section (RWW)

0x0000 - 0x07FF

No Read-While-Write section (NRWW)

0x0800 - 0x0FFF

Table 23-10. Explanation of different variables used in Figure 23-4 and the mapping to the Z-pointer

Variable

Corresponding

Z-value

Description(1)

PCMSB

Most significant bit in the Program Counter. (The Program

Counter is 13 bits PC[12:0])

PAGEMSB

Most significant bit which is used to address the words within

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

ZPCMSB

Z13

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[12:6]

Z13: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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