Table 25-7. Read-While-Write Limit(1)
Section
Pages
112
Address
Read-While-Write section (RWW)
No Read-While-Write section (NRWW)
0x0000 - 0x1BFF
0x1C00 - 0x1FFF
16
Note:
1. For details about these two section, see ”NRWW – No Read-While-Write Section” on page
280 and ”RWW – Read-While-Write Section” on page 280.
Table 25-8. Explanation of different variables used in Figure 25-3 and the mapping to the Z-
pointer(1)
Corresponding
Variable
Z-value
Description
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
Bit in Z-register that is mapped to PCMSB. Because Z0
is not used, the ZPCMSB equals PCMSB + 1.
ZPCMSB
ZPAGEMSB
PCPAGE
Z13
Z6
Bit in Z-register that is mapped to PAGEMSB. Because
Z0 is not used, the ZPAGEMSB equals PAGEMSB + 1.
Program Counter page address: Page select, for Page
Erase and Page Write
PC[12:6]
PC[5:0]
Z13:Z7
Program Counter word address: Word select, for filling
temporary buffer (must be zero during Page Write
operation)
PCWORD
Z6:Z1
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.
292
ATmega169P
8018A–AVR–03/06
ATMEL [ ATMEL ]
