ATmega640/1280/1281/2560/2561
Table 141. Explanation of different variables used in Figure 138 and the mapping to the
Z-pointer, ATmega640
Corresponding
Variable
Z-value(2)
Description(1)
PAGEMSB
6
Most significant bit which is used to address the
words within one page (128 words in a page
requires seven bits PC [6:0]).
ZPCMSB
Z15
Z7
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[14:7]
PC[6:0]
Z15:Z8
Z7:Z1
Program Counter page address: Page select,
for Page Erase and Page Write
PCWORD
Program Counter word address: Word select,
for filling temporary buffer (must be zero during
Page Write operation)
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 322 for details about
the use of Z-pointer during Self-Programming.
ATmega1280/1281 Boot
Loader Parameters
In Table 142 through Table 143, the parameters used in the description of the Self-Pro-
gramming are given.
Table 142. Boot Size Configuration, ATmega1280/1281(1)
512
words
0x0000 -
0xFDFF
0xFE00 -
0xFFFF
1
1
0
1
0
1
0
4
8
0xFDFF
0xFBFF
0xF7FF
0xEFFF
0xFE00
0xFC00
0xF800
0xF000
1024
words
0x0000 -
0xFBFF
0xFC00 -
0xFFFF
2048
words
0x0000 -
0xF7FF
0xF800 -
0xFFFF
16
32
4096
words
0x0000 -
0xEFFF
0xF000 -
0xFFFF
0
Note:
1. The different BOOTSZ Fuse configurations are shown in Figure 137.
Table 143. Read-While-Write Limit, ATmega1280/1281
Section(1)
Pages
Address
Read-While-Write section (RWW)
No Read-While-Write section (NRWW)
480
32
0x0000 - 0xEFFF
0xF000 - 0xFFFF
331
2549A–AVR–03/05
ATMEL [ ATMEL ]
