ATmega16U4 datasheet(401/408 Pages) ATMEL

401 / 408 page

401

7766D–AVR–01/09

ATmega16U4/ATmega32U4

Table of Contents

Pin Configurations ................................................................................... 3

Overview ................................................................................................... 3

2.1 Block Diagram ..........................................................................................................4

2.2 Pin Descriptions ........................................................................................................5

About ......................................................................................................... 8

3.1 Disclaimer .................................................................................................................8

3.2 Resources ................................................................................................................8

3.3 Code Examples ........................................................................................................8

3.4 Data Retention ..........................................................................................................8

AVR CPU Core .......................................................................................... 9

4.1 Introduction ...............................................................................................................9

4.2 Architectural Overview ..............................................................................................9

4.3 ALU – Arithmetic Logic Unit ....................................................................................10

4.4 Status Register .......................................................................................................11

4.5 General Purpose Register File ...............................................................................12

4.6 Stack Pointer ..........................................................................................................13

4.7 Instruction Execution Timing ..................................................................................14

4.8 Reset and Interrupt Handling ..................................................................................15

AVR ATmega16U4/ATmega32U4 Memories ........................................ 18

5.1 In-System Reprogrammable Flash Program Memory ............................................18

5.2 SRAM Data Memory ...............................................................................................19

5.3 EEPROM Data Memory .........................................................................................21

5.4 I/O Memory .............................................................................................................26

System Clock and Clock Options ......................................................... 27

6.1 Clock Systems and their Distribution ......................................................................27

6.2 Clock Sources ........................................................................................................28

6.3 Low Power Crystal Oscillator ..................................................................................29

6.4 Low Frequency Crystal Oscillator ...........................................................................31

6.5 Calibrated Internal RC Oscillator ............................................................................32

6.6 External Clock ........................................................................................................33

6.7 Clock Output Buffer ................................................................................................37

6.8 System Clock Prescaler .........................................................................................37

6.9 PLL .........................................................................................................................39

ATmega16U4 Datasheet(PDF) 401 Page - ATMEL Corporation