Data Sheet

i
2545K–AVR–04/07
Table of Contents
Features ..................................................................................................... 1
1 Pin Configurations ................................................................................... 2
1.1 Pin Descriptions .......................................................................................................3
2 Overview ................................................................................................... 5
2.1 Block Diagram ..........................................................................................................5
2.2 Comparison Between ATmega48, ATmega88, and ATmega168 ............................6
3 Resources ................................................................................................. 7
4 About Code Examples ............................................................................. 8
5 AVR CPU Core .......................................................................................... 9
5.1 Overview ..................................................................................................................9
5.2 Architectural Overview .............................................................................................9
5.3 ALU – Arithmetic Logic Unit ...................................................................................10
5.4 Status Register .......................................................................................................11
5.5 General Purpose Register File ...............................................................................12
5.6 Stack Pointer ..........................................................................................................13
5.7 Instruction Execution Timing ..................................................................................14
5.8 Reset and Interrupt Handling .................................................................................15
6 AVR Memories ........................................................................................ 17
6.1 Overview ................................................................................................................17
6.2 In-System Reprogrammable Flash Program Memory ............................................17
6.3 SRAM Data Memory ..............................................................................................19
6.4 EEPROM Data Memory .........................................................................................20
6.5 I/O Memory .............................................................................................................21
6.6 Register Description ...............................................................................................22
7 System Clock and Clock Options ......................................................... 27
7.1 Clock Systems and their Distribution ......................................................................27
7.2 Clock Sources ........................................................................................................28
7.3 Low Power Crystal Oscillator ..................................................................................29
7.4 Full Swing Crystal Oscillator ...................................................................................31
7.5 Low Frequency Crystal Oscillator ...........................................................................33
7.6 Calibrated Internal RC Oscillator ............................................................................33
7.7 128 kHz Internal Oscillator .....................................................................................34