ATMEGA644 datasheet(19/374 Pages) ATMEL

19 / 374 page

2593L–AVR–02/07

ATmega644

Figure 6-1.

Program Memory Map

6.2

SRAM Data Memory

Figure 6-2 shows how the ATmega644 SRAM Memory is organized.

The ATmega644 is a complex microcontroller with more peripheral units than can be supported

within the 64 location reserved in the Opcode for the IN and OUT instructions. For the Extended

I/O space from $060 - $0FF in SRAM, only the ST/STS/STD and LD/LDS/LDD instructions can

be used.

The first 4,352 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 4,096 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.

Application Flash Section

Boot Flash Section

ATMEGA644 Datasheet(PDF) 19 Page - ATMEL Corporation