239
7799D–AVR–11/10
ATmega8U2/16U2/32U2
23.8.14
ATmega8U2 Boot Loader Parameters
(Page size = 64 words = 128 bytes)
Note:
1. The different BOOTSZ Fuse configurations are shown in
Figure 23-2.
Note:
Note:
1. Z0: should be zero for all SPM commands, byte select for the (E)LPM instruction.
Programming.
Table 23-8.
Boot Size Configuration
(1)(Word Addresses)
BOOTSZ1
BOOTSZ0
Boot
Size
Pages
Application
Flash
Section
Boot
Loader
Flash
Section
End
Application
Section
Boot
Reset
Address
(Start
Boot
Loader
Section)
1
256 words
4
0x0000 - 0xEFF
0xF00 - 0xFFF
0xEFF
0xF00
1
0
512 words
8
0x0000 - 0xDFF
0xE00 - 0xFFF
0xDFF
0xE00
0
1
1024 words
16
0x0000 - 0xBFF
0xC00 - 0xFFF
0xBFF
0xC00
0
2048 words
32
0x0000 - 0x7FF
0x800 - 0xFFF
0x7FF
0x800
Table 23-9.
Read-While-Write Limit
(1)Section
Pages
Address
Read-While-Write section (RWW)
32
0x0000 - 0x07FF
No Read-While-Write section (NRWW)
32
0x0800 - 0x0FFF
Table 23-10.
Explanation of different variables used in
Figure 23-4 and the mapping to the Z-pointer
Variable
Corresponding
Z-value
PCMSB
12
Most significant bit in the Program Counter. (The Program
Counter is 13 bits PC[12:0])
PAGEMSB
5
Most significant bit which is used to address the words within
one page (64 words in a page requires six bits PC [5:0]).
ZPCMSB
Z13
Bit in Z-pointer that is mapped to PCMSB. Because Z0 is not
used, the ZPCMSB equals PCMSB + 1.
ZPAGEMSB
Z6
Bit in Z-pointer that is mapped to PCMSB. 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)