ATtiny261A datasheet(15/292 Pages) ATMEL

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8197A–AVR–10/09

ATtiny261A/461A/861A

5. Memories

This section describes the different memories of the ATtiny261A/461A/861A. The AVR architec-

ture has two main memory spaces, the Data memory and the Program memory space. In

addition, the ATtiny261A/461A/861A features an EEPROM Memory for data storage. All three

memory spaces are linear and regular.

5.1

In-System Re-programmable Flash Program Memory

The ATtiny261A/461A/861A contains 2/4/8K byte On-chip In-System Reprogrammable Flash

memory for program storage. Since all AVR instructions are 16 or 32 bits wide, the Flash is orga-

nized as 1024/2048/4096 x 16.

The Flash memory has an endurance of at least 10,000 write/erase cycles. The

ATtiny261A/461A/861A Program Counter (PC) is 10/11/12 bits wide, thus capable of addressing

the 1024/2048/4096 Program memory locations. “Memory Programming” on page 167 contains

a detailed description on Flash data serial downloading using the SPI pins.

Constant tables can be allocated within the entire address space of program memory (see the

LPM – Load Program memory instruction description).

Timing diagrams for instruction fetch and execution are presented in “Instruction Execution Tim-

ing” on page 12.

Figure 5-1.

Program Memory Map

5.2

SRAM Data Memory

Figure 5-2 on page 16 shows how the ATtiny261A/461A/861A SRAM Memory is organized.

The lower data memory locations address both the Register File, the I/O memory and the inter-

nal data SRAM. The first 32 locations address the Register File, the next 64 locations the

standard I/O memory, and the last 128/256/512 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.

0x0000

0x03FF/0x07FF/0x0FFF

Program Memory

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