ATmega325P datasheet(20/364 Pages) ATMEL

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8023F–AVR–07/09

ATmega325P/3250P

Figure 7-1.

Program Memory Map

7.3

SRAM Data Memory

Figure 7-2 shows how the ATmega325P/3250P SRAM Memory is organized.

The ATmega325P/3250P is a complex microcontroller with more peripheral units than can be

supported 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

instructions can be used.

The lower 2304 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 2,048 bytes of internal data SRAM in the ATmega325P/3250P are all accessible through all

0x0000

0x3FFF

Program Memory

Application Flash Section

Boot Flash Section

ATmega325P データシート(PDF) 20 Page - ATMEL Corporation