Datasheet

Note: For details about these two section, see NRWW – No Read-While-Write Section and RWW –

Read-While-Write Section.

Table 28-8. Explanation of Different Variables used in Figure and the Mapping to the Z-pointer,

ATmega8A

Variable Corresponding Z-

value

(1)

Description

PCMSB 11 Most significant bit in the Program Counter. (The Program

Counter is 12 bits PC[11:0])

PAGEMSB 4 Most significant bit which is used to address the words

within one page (32 words in a page requires 5 bits PC

[4:0]).

ZPCMSB Z12 Bit in Z-register that is mapped to PCMSB. Because Z0 is

not used, the ZPCMSB equals PCMSB + 1.

ZPAGEMSB Z5 Bit in Z-register that is mapped to PAGEMSB. Because

Z0 is not used, the ZPAGEMSB equals PAGEMSB + 1.

PCPAGE PC[11:5] Z12:Z6 Program counter page address: Page select, for page

erase and page write

PCWORD PC[4:0] Z5:Z1 Program counter word address: Word select, for filling

temporary buffer (must be zero during page write

operation)

Note: 1.

Z15:Z13: always ignored.

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

See Addressing the Flash During Self-Programming for details about the use of Z-pointer during Self-

Programming.

28.9 Register Description

AVR 8-Bit Microcontroller

BTLDR - Boot Loader Support – Read-While-Wri...

Datasheet Complete

40001974A-page 285