Datasheet

i
2549O–AVR–05/12
ATmega640/1280/1281/2560/2561
Table of Contents
Features ..................................................................................................... 1
1 Pin Configurations ................................................................................... 2
2 Overview ................................................................................................... 5
2.1 Block Diagram ...................................................................................................5
2.2 Comparison Between ATmega1281/2561 and ATmega640/1280/2560 ...........7
2.3 Pin Descriptions .................................................................................................7
3 Resources ............................................................................................... 11
4 About Code Examples ........................................................................... 11
5 Data Retention ........................................................................................ 11
6 Capacitive touch sensing ...................................................................... 11
7 AVR CPU Core ........................................................................................ 12
7.1 Introduction ......................................................................................................12
7.2 Architectural Overview .....................................................................................12
7.3 ALU – Arithmetic Logic Unit .............................................................................13
7.4 Status Register ................................................................................................14
7.5 General Purpose Register File ........................................................................15
7.6 Stack Pointer ...................................................................................................16
7.7 Instruction Execution Timing ...........................................................................17
7.8 Reset and Interrupt Handling ...........................................................................18
8 AVR Memories ........................................................................................ 21
8.1 In-System Reprogrammable Flash Program Memory .....................................21
8.2 SRAM Data Memory ........................................................................................21
8.3 EEPROM Data Memory ..................................................................................23
8.4 I/O Memory ......................................................................................................27
9 External Memory Interface .................................................................... 28
9.1 Overview ..........................................................................................................28
9.2 Register Description ........................................................................................35
9.3 General Purpose registers ...............................................................................37
9.4 External Memory registers ...............................................................................37
10 System Clock and Clock Options ......................................................... 40
10.1 Overview ..........................................................................................................40