Datasheet

279
2545F–AVR–06/05
ATmega48/88/168
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 270 for details about the use of
Z-pointer during Self-Programming.
Table 25-11. Explanation of Different Variables used in Figure 25-3 and the Mapping to the Z-
pointer, ATmega168
Variable
Corresponding
Z-value
(1)
Description
PCMSB 12
Most significant bit in the Program Counter. (The
Program Counter is 12 bits PC[11:0])
PAGE MS B 5
Most significant bit which is used to address
the words within one page (64 words in a page
requires 6 bits PC [5:0])
ZPCMSB Z13
Bit in Z-register that is mapped to PCMSB. Because
Z0 is not used, the ZPCMSB equals PCMSB + 1.
ZPAGEMSB Z6
Bit in Z-register that is mapped to PAGEMSB.
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)