Table 29-12. Explanation of different variables used in Figure 29-3 and the mapping to the Z-
pointer, ATmega1280/1281
Corresponding
Variable
Z-value(2)
Description(1)
Most significant bit which is used to address the
words within one page (128 words in a page
requires seven bits PC [6:0]).
PAGEMSB
6
Bit in Z-pointer that is mapped to PCMSB. Because
Z0 is not used, the ZPCMSB equals PCMSB + 1.
ZPCMSB
ZPAGEMSB
PCPAGE
Z16(3)
Z7
Bit in Z-pointer that is mapped to PCMSB. Because
Z0 is not used, the ZPAGEMSB equals PAGEMSB +
1.
Program Counter page address: Page select, for
Page Erase and Page Write
PC[15:7]
PC[6:0]
Z16(3):Z8
Z7:Z1
Program Counter word address: Word select, for
filling temporary buffer (must be zero during Page
Write operation)
PCWORD
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 323 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.
29.6.16 ATmega2560/2561 Boot Loader Parameters
In Table 29-13 through Table 29-15, the parameters used in the description of the Self-Program-
ming are given.
Table 29-13. Boot Size Configuration, ATmega2560/2561(1)
512
words
0x00000 -
0x1FDFF
0x1FE00 -
0x1FFFF
1
1
0
0
1
0
1
0
4
8
0x1FDFF
0x1FBFF
0x1F7FF
0x1EFFF
0x1FE00
0x1FC00
0x1F800
0x1F000
1024
words
0x00000 -
0x1FBFF
0x1FC00 -
0x1FFFF
2048
words
0x00000 -
0x1F7FF
0x1F800 -
0x1FFFF
16
32
4096
words
0x00000 -
0x1EFFF
0x1F000 -
0x1FFFF
Note:
1. The different BOOTSZ Fuse configurations are shown in Figure 29-2.
332
ATmega640/1280/1281/2560/2561
2549L–AVR–08/07
ATMEL [ ATMEL ]
