Atmel ATmega48A

i
8271D–AVR–05/11
ATmega48A/PA/88A/PA/168A/PA/328/P
Table of Contents
Features ..................................................................................................... 1
1 Pin Configurations ................................................................................... 2
1.1Pin Descriptions ........................................................................................................3
2 Overview ................................................................................................... 5
2.1Block Diagram ...........................................................................................................5
2.2Comparison Between Processors .............................................................................6
3 Resources ................................................................................................. 8
4 Data Retention .......................................................................................... 8
5 About Code Examples ............................................................................. 8
6 Capacitive Touch Sensing ...................................................................... 8
7 AVR CPU Core .......................................................................................... 9
7.1Overview ...................................................................................................................9
7.2ALU – Arithmetic Logic Unit ....................................................................................10
7.3Status Register ........................................................................................................10
7.4General Purpose Register File ................................................................................12
7.5Stack Pointer ...........................................................................................................13
7.6Instruction Execution Timing ...................................................................................14
7.7Reset and Interrupt Handling ..................................................................................15
8 AVR Memories ........................................................................................ 17
8.1Overview .................................................................................................................17
8.2In-System Reprogrammable Flash Program Memory .............................................17
8.3SRAM Data Memory ...............................................................................................19
8.4EEPROM Data Memory ..........................................................................................20
8.5I/O Memory ..............................................................................................................21
8.6Register Description ................................................................................................22
9 System Clock and Clock Options ......................................................... 27
9.1Clock Systems and their Distribution .......................................................................27
9.2Clock Sources .........................................................................................................28
9.3Low Power Crystal Oscillator ...................................................................................29
9.4Full Swing Crystal Oscillator ....................................................................................31
9.5Low Frequency Crystal Oscillator ............................................................................33