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2545M–AVR–09/07
ATmega48/88/168
Features ..................................................................................................... 1
1 Pin Configurations ...................................................................................2
1.1Pin Descriptions .........................................................................................................3
2 Overview ................................................................................................... 5
2.1Block Diagram ...........................................................................................................5
2.2Comparison Between ATmega48, ATmega88, and ATmega168 .............................6
3 Resources ................................................................................................. 7
4 Data Retention ..........................................................................................8
5 About Code Examples ............................................................................. 9
6 AVR CPU Core ........................................................................................ 10
6.1Overview ..................................................................................................................10
6.2Architectural Overview .............................................................................................10
6.3ALU – Arithmetic Logic Unit .....................................................................................11
6.4Status Register ........................................................................................................12
6.5General Purpose Register File ................................................................................13
6.6Stack Pointer ...........................................................................................................14
6.7Instruction Execution Timing ...................................................................................15
6.8Reset and Interrupt Handling ...................................................................................16
7 AVR Memories ........................................................................................18
7.1Overview ..................................................................................................................18
7.2In-System Reprogrammable Flash Program Memory .............................................18
7.3SRAM Data Memory ................................................................................................20
7.4EEPROM Data Memory ..........................................................................................21
7.5I/O Memory ..............................................................................................................22
7.6Register Description ................................................................................................23
8 System Clock and Clock Options .........................................................28
8.1Clock Systems and their Distribution .......................................................................28
8.2Clock Sources .........................................................................................................29
8.3Low Power Crystal Oscillator ...................................................................................30
8.4Full Swing Crystal Oscillator ....................................................................................32
8.5Low Frequency Crystal Oscillator ............................................................................34
8.6Calibrated Internal RC Oscillator .............................................................................34
8.7128 kHz Internal Oscillator ......................................................................................35
