ATMEGA48_11 Datasheet, PDF (17/377 Pages) ATMEL Corporation – High performance, low power Atmel AVR 8-bit microcontroller Advanced RISC architecture

ATmega48/88/168
8. AVR memories
8.1 Overview
This section describes the different memories in the Atmel ATmega48/88/168. The AVR archi-
tecture has two main memory spaces, the Data Memory and the Program Memory space. In
addition, the ATmega48/88/168 features an EEPROM Memory for data storage. All three mem-
ory spaces are linear and regular.
8.2 In-system reprogrammable flash program memory
The ATmega48/88/168 contains 4K/8K/16K bytes 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 2K/4K/8K × 16. For software security, the Flash Program memory space is divided into
two sections, Boot Loader Section and Application Program Section in ATmega88 and
ATmega168. ATmega48 does not have separate Boot Loader and Application Program sec-
tions, and the SPM instruction can be executed from the entire Flash. See SELFPRGEN
description in section “SPMCSR – Store program memory control and status register” on page
267 and page 283for more details.
The Flash memory has an endurance of at least 10,000 write/erase cycles. The
ATmega48/88/168 Program Counter (PC) is 11/12/13 bits wide, thus addressing the 2K/4K/8K
program memory locations. The operation of Boot Program section and associated Boot Lock
bits for software protection are described in detail in “Self-programming the flash, Atmel
ATmega48” on page 262 and “Boot loader support – Read-while-write self-programming, Atmel
ATmega88 and Atmel ATmega168” on page 269. “Memory programming” on page 285 contains
a detailed description on Flash Programming in SPI- or Parallel Programming mode.
Constant tables can be allocated within the entire program memory address space (see the LPM
– Load Program Memory instruction description).
Timing diagrams for instruction fetch and execution are presented in “Instruction execution tim-
ing” on page 14.
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