Atmel XMEGA B, User Manual

Page: 20 / 415

20 XMEGA B [DATASHEET]
8291B–AVR–01/2013
4. Memories
4.1 Features

Flash program memory

One linear address space

In-system programmable

Self-programming and boot loader support

Application section for application code

Application table section for application code or data storage

Boot section for application code or bootloader code

Separate read/write protection lock bits for all sections

Built in fast CRC check of a selectable flash program memory section

Data memory

One linear address space

Single-cycle access from CPU

SRAM

EEPROM

Byte and page accessible

Optional memory mapping for direct load and store

I/O memory

Configuration and status registers for all peripherals and modules

16 bit-accessible general purpose registers for global variables or flags

Bus arbitration

Safe and deterministic handling of priority between CPU, DMA controller, and other bus masters

Separate buses for SRAM, EEPROM and I/O memory access

Simultaneous bus access for CPU and DMA controller

Production signature row memory for factory programmed data

ID for each microcontroller device type

Serial number for each device

Calibration bytes for factory calibrated peripherals

User signature row

One flash page in size

Can be read and written from software

Content is kept after chip erase
4.2 Overview
This section describes the different memory sections. The AVR architecture has two main memory spaces, the program
memory and the data memory. Executable code can reside only in the program memory, while data can be stored in the
program memory and the data memory. The data memory includes the internal SRAM, and as well as EEPROM for
nonvolatile data storage. All memory spaces are linear and require no memory bank switching. Nonvolatile memory
(NVM) spaces can be locked for further write and read/write operations. This prevents unrestricted access to the
application software.
A separate memory section contains the fuse bytes. These are used for configuring important system functions, and can
only be written by an external programmer.
4.3 Flash Program Memory
All XMEGA devices contain on-chip, in-system reprogrammable flash memory for program storage. The flash memory
can be accessed for read and write from an external programmer through the PDI or from application software running in
the device.