20
2467S–AVR–07/09
ATmega128
The Indirect with Displacement mode reaches 63 address locations from the base address given
by the Y- or Z-register.
When using register indirect addressing modes with automatic pre-decrement and post-incre-
ment, the address registers X, Y, and Z are decremented or incremented.
The 32 general purpose working registers, 64 I/O registers, and the 4096 bytes of internal data
SRAM in the ATmega128 are all accessible through all these addressing modes. The Register
file is described in “General Purpose Register File” on page 12.
Figure 9. Data Memory Map
Memory Configuration B
32 Registers
64 I/O Registers
Internal SRAM
(4000 x 8)
$0000 - $001F
$0020 - $005F
$1000
$0FFF
$FFFF
$0060
Data Memory
External SRAM
(0 - 64K x 8)
Memory Configuration A
32 Registers
64 I/O Registers
Internal SRAM
(4096 x 8)
$0000 - $001F
$0020 - $005F
$1100
$10FF
$FFFF
$0060 - $00FF
Data Memory
External SRAM
(0 - 64K x 8)
160 Ext I/O Reg.
$0100
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