ATmega328P datasheet(17/345 Pages) ATMEL

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7810A–AVR–11/09

ATmega328P [Preliminary]

Figure 7-1.

Program Memory Map ATmega328P

7.3

SRAM Data Memory

Figure 7-2 shows how the ATmega328P SRAM Memory is organized.

The ATmega328P is a complex microcontroller with more peripheral units than can be sup-

ported within the 64 locations reserved in the Opcode for the IN and OUT instructions. For the

Extended I/O space from 0x60 - 0xFF in SRAM, only the ST/STS/STD and LD/LDS/LDD instruc-

tions can be used.

The lower 2303 data memory locations address both the Register File, the I/O memory,

Extended I/O memory, and the internal data SRAM. The first 32 locations address the Register

File, the next 64 location the standard I/O memory, then 160 locations of Extended I/O memory,

and the next 2048 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- 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, 160 Extended I/O Registers, and

the 2048 bytes of internal data SRAM in the ATmega328P are all accessible through all these

addressing modes. The Register File is described in “General Purpose Register File” on page

11.

0x0000

0x3FFF

Program Memory

Application Flash Section

Boot Flash Section

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