ATmega8U2/16U2/32U2
23.8.15 ATmega16U2 Boot Loader Parameters
In Table 23-11 through Table 23-13, the parameters used in the description of the Self-Programming are given.
Table 23-11. Boot Size Configuration(1)(Word Addresses)
1
1
0
0
1
0
1
0
256 words
512 words
1024 words
2048 words
4
0x0000 - 0x1EFF
0x0000 - 0x1DFF
0x0000 - 0x1BFF
0x0000 - 0x17FF
0x1F00 - 0x1FFF
0x1E00 - 0x1FFF
0x1C00 - 0x1FFF
0x1800 - 0x1FFF
0x1EFF
0x1DFF
0x1BFF
0x17FF
0x1F00
0x1E00
0x1C00
0x1800
8
16
32
(Page size = 64 words = 128 bytes)
Note:
1. The different BOOTSZ Fuse configurations are shown in Figure 23-2.
Table 23-12. Read-While-Write Limit(1)
Section
Pages
96
Address
Read-While-Write section (RWW)
No Read-While-Write section (NRWW)
0x0000 - 0x17FF
0x1800 - 0x1FFF
32
Note:
1. For details about these two section, see “NRWW – No Read-While-Write Section” on page 227 and “RWW – Read-While-
Write Section” on page 227.
Table 23-13. Explanation of different variables used in Figure 23-4 and the mapping to the Z-pointer
Corresponding
Variable
Z-value
Description(1)
Most significant bit in the Program Counter. (The Program
Counter is 13 bits PC[12:0])
PCMSB
12
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]).
PAGEMSB
ZPCMSB
Bit in Z-pointer that is mapped to PCMSB. Because Z0 is not
used, the ZPCMSB equals PCMSB + 1.
Z13
Z6
Bit in Z-pointer that is mapped to PCMSB. Because Z0 is not
used, the ZPAGEMSB equals PAGEMSB + 1.
ZPAGEMSB
PCPAGE
Program Counter page address: Page select, for Page Erase
and Page Write
PC[12:6]
PC[5:0]
Z13:Z7
Z6:Z1
Program Counter word address: Word select, for filling
temporary buffer (must be zero during Page Write operation)
PCWORD
Note:
1. Z0: should be zero for all SPM commands, byte select for the (E)LPM instruction.
See “Addressing the Flash During Self-Programming” on page 232 for details about the use of Z-pointer during Self-
Programming.
240
7799D–AVR–11/10
ATMEL [ ATMEL ]
