ATXMEGA128A4 Datasheet, PDF (6/69 Pages) ATMEL Corporation – 8/16-bit XMEGA A4 Microcontroller

XMEGA A4
6. AVR CPU
6.1 Features
6.2 Overview
• 8/16-bit high performance AVR RISC Architecture
– 138 instructions
– Hardware multiplier
• 32x8-bit registers directly connected to the ALU
• Stack in RAM
• Stack Pointer accessible in I/O memory space
• Direct addressing of up to 16M Bytes of program and data memory
• True 16/24-bit access to 16/24-bit I/O registers
• Support for 8-, 16- and 32-bit Arithmetic
• Configuration Change Protection of system critical features
The XMEGA A4 uses the 8/16-bit AVR CPU. The main function of the CPU is program execu-
tion. The CPU must therefore be able to access memories, perform calculations and control
peripherals. Interrupt handling is described in a separate section. Figure 6-1 on page 6 shows
the CPU block diagram.
Figure 6-1. CPU block diagram
DATA BUS
Program
Counter
OCD
Flash
Program
Memory
Instruction
Register
32 x 8 General
Purpose
Registers
STATUS/
CONTROL
Instruction
Decode
8069C–AVR–06/08
ALU
Multiplier/
DES
Peripheral
Module 1
Peripheral
Module 2
DATA BUS
SRAM
EEPROM
PMIC
The AVR uses a Harvard architecture - with separate memories and buses for program and
data. Instructions in the program memory are executed with a single level pipeline. While one
instruction is being executed, the next instruction is pre-fetched from the program memory. This
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