ATMEGA8 datasheet(18/331 Pages) ATMEL

18 / 331 page

2486AA–AVR–02/2013

ATmega8(L)

SRAM Data

Memory

Figure 8 shows how the Atmel

®AVR® SRAM Memory is organized.

The lower 1120 Data memory locations address the Register File, the I/O Memory, and the inter-

nal data SRAM. The first 96 locations address the Register File and I/O Memory, and the next

1024 locations address the internal data SRAM.

The five different addressing modes for the Data memory cover: Direct, Indirect with Displace-

ment, Indirect, Indirect with Pre-decrement, and Indirect with Post-increment. In the Register

File, registers R26 to R31 feature the indirect addressing pointer registers.

The direct addressing reaches the entire data space.

The Indirect with Displacement mode reaches 63 address locations from the base address given

by the Y-register 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 1024 bytes of internal data

SRAM in the ATmega8 are all accessible through all these addressing modes. The Register File

is described in “General Purpose Register File” on page 12.

Figure 8. Data Memory Map

R29

R30

R31

I/O Registers

$00

$01

$02

...

$3D

$3E

$3F

...

$0000

$0001

$0002

$001D

$001E

$001F

$0020

$0021

$0022

...

$005D

$005E

$005F

...

Data Address Space

$0060

$0061

$045E

$045F

...

Internal SRAM

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