293
8271D–AVR–05/11
ATmega48A/PA/88A/PA/168A/PA/328/P
27.8.15 ATmega168A and ATmega168PA Boot Loader Parameters
In Table 27-10 through Table 27-12, the parameters used in the description of the self programming are given.
Note: The different BOOTSZ Fuse configurations are shown in Figure 27-2 on page 283.
For details about these two section, see ”NRWW – No Read-While-Write Section” on page 281 and ”RWW – Read-While-
Write Section” on page 281
Note: 1. Z15:Z14: always ignored
Z0: should be zero for all SPM commands, byte select for the LPM instruction.
See ”Addressing the Flash During Self-Programming” on page 285 for details about the use of Z-pointer during Self-
Programming.
Table 27-10. Boot Size Configuration, ATmega168A/168PA
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 2 0x0000 - 0x1F7F 0x1F80 - 0x1FFF 0x1F7F 0x1F80
1 0 256 words 4 0x0000 - 0x1EFF 0x1F00 - 0x1FFF 0x1EFF 0x1F00
0 1 512 words 8 0x0000 - 0x1DFF 0x1E00 - 0x1FFF 0x1DFF 0x1E00
0 0 1024 words 16 0x0000 - 0x1BFF 0x1C00 - 0x1FFF 0x1BFF 0x1C00
Table 27-11. Read-While-Write Limit, ATmega168A/168PA
Section Pages Address
Read-While-Write section (RWW) 112 0x0000 - 0x1BFF
No Read-While-Write section (NRWW) 16 0x1C00 - 0x1FFF
Table 27-12. Explanation of Different Variables used in Figure 27-3 and the Mapping to the Z-pointer,
ATmega168A/168PA
Variable
Corresponding
Z-value
(1)
Description
PCMSB 12
Most significant bit in the Program Counter. (The Program Counter
is 13 bits PC[12:0])
PAG E MS B 5
Most significant bit which is used to address the words within
one page (64 words in a page requires 6 bits PC [5:0])
ZPCMSB Z13
Bit in Z-register that is mapped to PCMSB. Because Z0 is not used,
the ZPCMSB equals PCMSB + 1.
ZPAGEMSB Z6
Bit in Z-register that is mapped to PAGEMSB. 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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