28.8.13 ATmega8A Boot Loader Parameters

In the following tables, the parameters used in the description of the self programming are given.

Table 28-6. Boot Size Configuration, ATmega8A
BOOTSZ1	BOOTSZ0	Boot Size	Pages	Application Flash Section	Boot Loader Flash Section	End Application Section	Boot Reset Address (Start Boot Loader Section)
1	1	128 words	4	0x000 - 0xF7F	0xF80 - 0xFFF	0xF7F	0xF80
1	0	256 words	8	0x000 - 0xEFF	0xF00 - 0xFFF	0xEFF	0xF00
0	1	512 words	16	0x000 - 0xDFF	0xE00 - 0xFFF	0xDFF	0xE00
0	0	1024 words	32	0x000 - 0xBFF	0xC00 - 0xFFF	0xBFF	0xC00

Note: The different BOOTSZ Fuse configurations are shown in Figure 28-2.

Table 28-7. Read-While-Write Limit, ATmega8A
Section	Pages	Address
Read-While-Write section (RWW)	96	0x000 - 0xBFF
No Read-While-Write section (NRWW)	32	0xC00 - 0xFFF

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.