Data Sheet

ManualsBrandsGravitech ManualsArduinoArduino Nano USB Microcontroller v3

Table Of Contents

Features
1. Pin Configurations
- 1.1 Pin Descriptions
2. Overview
- 2.1 Block Diagram
- 2.2 Comparison Between ATmega48, ATmega88, and ATmega168
3. Resources
4. About Code Examples
5. AVR CPU Core
- 5.1 Overview
- 5.2 Architectural Overview
- 5.3 ALU - Arithmetic Logic Unit
- 5.4 Status Register
  - 5.4.1 SREG - AVR Status Register
- 5.5 General Purpose Register File
  - 5.5.1 The X-register, Y-register, and Z-register
- 5.6 Stack Pointer
  - 5.6.1 SPH and SPL - Stack Pointer High and Stack Pointer Low Register
- 5.7 Instruction Execution Timing
- 5.8 Reset and Interrupt Handling
  - 5.8.1 Interrupt Response Time
6. AVR Memories
- 6.1 Overview
- 6.2 In-System Reprogrammable Flash Program Memory
- 6.3 SRAM Data Memory
  - 6.3.1 Data Memory Access Times
- 6.4 EEPROM Data Memory
  - 6.4.1 EEPROM Read/Write Access
  - 6.4.2 Preventing EEPROM Corruption
- 6.5 I/O Memory
  - 6.5.1 General Purpose I/O Registers
- 6.6 Register Description
7. System Clock and Clock Options
- 7.1 Clock Systems and their Distribution
- 7.2 Clock Sources
  - 7.2.1 Default Clock Source
  - 7.2.2 Clock Startup Sequence
- 7.3 Low Power Crystal Oscillator
- 7.4 Full Swing Crystal Oscillator
- 7.5 Low Frequency Crystal Oscillator
- 7.6 Calibrated Internal RC Oscillator
- 7.7 128 kHz Internal Oscillator
- 7.8 External Clock
- 7.9 Clock Output Buffer
- 7.10 Timer/Counter Oscillator
- 7.11 System Clock Prescaler
- 7.12 Register Description
  - 7.12.1 OSCCAL - Oscillator Calibration Register
  - 7.12.2 CLKPR - Clock Prescale Register
8. Power Management and Sleep Modes
- 8.1 Sleep Modes
- 8.2 Idle Mode
- 8.3 ADC Noise Reduction Mode
- 8.4 Power-down Mode
- 8.5 Power-save Mode
- 8.6 Standby Mode
- 8.7 Power Reduction Register
- 8.8 Minimizing Power Consumption
- 8.9 Register Description
  - 8.9.1 SMCR - Sleep Mode Control Register
  - 8.9.2 PRR - Power Reduction Register
9. System Control and Reset
- 9.1 Resetting the AVR
- 9.2 Reset Sources
- 9.3 Power-on Reset
- 9.4 External Reset
- 9.5 Brown-out Detection
- 9.6 Watchdog System Reset
- 9.7 Internal Voltage Reference
  - 9.7.1 Voltage Reference Enable Signals and Start-up Time
- 9.8 Watchdog Timer
  - 9.8.1 Features
- 9.9 Register Description
  - 9.9.1 MCUSR - MCU Status Register
  - 9.9.2 WDTCSR - Watchdog Timer Control Register
10. Interrupts
- 10.1 Overview
- 10.2 Interrupt Vectors in ATmega48
- 10.3 Interrupt Vectors in ATmega88
- 10.4 Interrupt Vectors in ATmega168
  - 10.4.1 Moving Interrupts Between Application and Boot Space, ATmega88 and ATmega168
- 10.5 Register Description
  - 10.5.1 MCUCR - MCU Control Register
11. External Interrupts
- 11.1 Pin Change Interrupt Timing
- 11.2 Register Description
12. I/O-Ports
- 12.1 Overview
- 12.2 Ports as General Digital I/O
- 12.3 Alternate Port Functions
- 12.4 Register Description
13. 8-bit Timer/Counter0 with PWM
- 13.1 Features
- 13.2 Overview
  - 13.2.1 Definitions
  - 13.2.2 Registers
- 13.3 Timer/Counter Clock Sources
- 13.4 Counter Unit
- 13.5 Output Compare Unit
- 13.6 Compare Match Output Unit
  - 13.6.1 Compare Output Mode and Waveform Generation
- 13.7 Modes of Operation
- 13.8 Timer/Counter Timing Diagrams
- 13.9 Register Description
14. 16-bit Timer/Counter1 with PWM
- 14.1 Features
- 14.2 Overview
  - 14.2.1 Registers
  - 14.2.2 Definitions
- 14.3 Accessing 16-bit Registers
  - 14.3.1 Reusing the Temporary High Byte Register
- 14.4 Timer/Counter Clock Sources
- 14.5 Counter Unit
- 14.6 Input Capture Unit
- 14.7 Output Compare Units
- 14.8 Compare Match Output Unit
  - 14.8.1 Compare Output Mode and Waveform Generation
- 14.9 Modes of Operation
- 14.10 Timer/Counter Timing Diagrams
- 14.11 Register Description
15. Timer/Counter0 and Timer/Counter1 Prescalers
- 15.0.1 Internal Clock Source
- 15.0.2 Prescaler Reset
- 15.0.3 External Clock Source
- 15.1 Register Description
  - 15.1.1 GTCCR - General Timer/Counter Control Register
16. 8-bit Timer/Counter2 with PWM and Asynchronous Operation
- 16.1 Features
- 16.2 Overview
  - 16.2.1 Registers
  - 16.2.2 Definitions
- 16.3 Timer/Counter Clock Sources
- 16.4 Counter Unit
- 16.5 Output Compare Unit
- 16.6 Compare Match Output Unit
  - 16.6.1 Compare Output Mode and Waveform Generation
- 16.7 Modes of Operation
- 16.8 Timer/Counter Timing Diagrams
- 16.9 Asynchronous Operation of Timer/Counter2
- 16.10 Timer/Counter Prescaler
- 16.11 Register Description
17. SPI - Serial Peripheral Interface
- 17.1 Features
- 17.2 Overview
- 17.3 SS Pin Functionality
  - 17.3.1 Slave Mode
  - 17.3.2 Master Mode
- 17.4 Data Modes
- 17.5 Register Description
18. USART0
- 18.1 Features
- 18.2 Overview
- 18.3 Clock Generation
- 18.4 Frame Formats
  - 18.4.1 Parity Bit Calculation
- 18.5 USART Initialization
- 18.6 Data Transmission - The USART Transmitter
- 18.7 Data Reception - The USART Receiver
- 18.8 Asynchronous Data Reception
- 18.9 Multi-processor Communication Mode
  - 18.9.1 Using MPCMn
- 18.10 Register Description
- 18.11 Examples of Baud Rate Setting
19. USART in SPI Mode
- 19.1 Features
- 19.2 Overview
- 19.3 Clock Generation
- 19.4 SPI Data Modes and Timing
- 19.5 Frame Formats
  - 19.5.1 USART MSPIM Initialization
- 19.6 Data Transfer
  - 19.6.1 Transmitter and Receiver Flags and Interrupts
  - 19.6.2 Disabling the Transmitter or Receiver
- 19.7 AVR USART MSPIM vs. AVR SPI
- 19.8 Register Description
20. 2-wire Serial Interface
- 20.1 Features
- 20.2 2-wire Serial Interface Bus Definition
  - 20.2.1 TWI Terminology
  - 20.2.2 Electrical Interconnection
- 20.3 Data Transfer and Frame Format
- 20.4 Multi-master Bus Systems, Arbitration and Synchronization
- 20.5 Overview of the TWI Module
- 20.6 Using the TWI
- 20.7 Transmission Modes
- 20.8 Multi-master Systems and Arbitration
- 20.9 Register Description
21. Analog Comparator
- 21.1 Overview
- 21.2 Analog Comparator Multiplexed Input
- 21.3 Register Description
22. Analog-to-Digital Converter
- 22.1 Features
- 22.2 Overview
- 22.3 Starting a Conversion
- 22.4 Prescaling and Conversion Timing
- 22.5 Changing Channel or Reference Selection
  - 22.5.1 ADC Input Channels
  - 22.5.2 ADC Voltage Reference
- 22.6 ADC Noise Canceler
- 22.7 ADC Conversion Result
- 22.8 Register Description
23. debugWIRE On-chip Debug System
- 23.1 Features
- 23.2 Overview
- 23.3 Physical Interface
- 23.4 Software Break Points
- 23.5 Limitations of debugWIRE
- 23.6 Register Description
  - 23.6.1 DWDR - debugWire Data Register
24. Self-Programming the Flash, ATmega48
- 24.1 Overview
- 24.2 Addressing the Flash During Self-Programming
- 24.3 Register Description
  - 24.3.1 SPMCSR - Store Program Memory Control and Status Register
25. Boot Loader Support - Read-While-Write Self-Programming, ATmega88 and ATmega168
- 25.1 Features
- 25.2 Overview
- 25.3 Application and Boot Loader Flash Sections
  - 25.3.1 Application Section
  - 25.3.2 BLS - Boot Loader Section
- 25.4 Read-While-Write and No Read-While-Write Flash Sections
  - 25.4.1 RWW - Read-While-Write Section
  - 25.4.2 NRWW - No Read-While-Write Section
- 25.5 Boot Loader Lock Bits
- 25.6 Entering the Boot Loader Program
- 25.7 Addressing the Flash During Self-Programming
- 25.8 Self-Programming the Flash
- 25.9 Register Description
  - 25.9.1 SPMCSR - Store Program Memory Control and Status Register
26. Memory Programming
- 26.1 Program And Data Memory Lock Bits
- 26.2 Fuse Bits
  - 26.2.1 Latching of Fuses
- 26.3 Signature Bytes
- 26.4 Calibration Byte
- 26.5 Page Size
- 26.6 Parallel Programming Parameters, Pin Mapping, and Commands
  - 26.6.1 Signal Names
- 26.7 Parallel Programming
- 26.8 Serial Downloading
27. Electrical Characteristics
- 27.1 Absolute Maximum Ratings*
- 27.2 DC Characteristics ATmega48/88/168*
- 27.3 Speed Grades
- 27.4 Clock Characteristics
- 27.5 System and Reset Characteristics
- 27.6 2-wire Serial Interface Characteristics
- 27.7 SPI Timing Characteristics
- 27.8 ADC Characteristics - Preliminary Data
- 27.9 Parallel Programming Characteristics
28. Typical Characteristics - Preliminary Data
- 28.1 Active Supply Current
- 28.2 Idle Supply Current
- 28.3 Supply Current of I/O modules
- 28.4 Power-Down Supply Current
- 28.5 Power-Save Supply Current
- 28.6 Standby Supply Current
- 28.7 Pin Pull-up
- 28.8 Pin Driver Strength
- 28.9 Pin Thresholds and Hysteresis
- 28.10 BOD Thresholds and Analog Comparator Offset
- 28.11 Internal Oscillator Speed
- 28.12 Current Consumption of Peripheral Units
- 28.13 Current Consumption in Reset and Reset Pulse width
29. Register Summary
30. Instruction Set Summary
31. Ordering Information
- 31.1 ATmega48
- 31.2 ATmega88
- 31.3 ATmega168
32. Packaging Information
- 32.1 32A
- 32.2 28M1
- 32.3 32M1-A
- 32.4 28P3
33. Errata
- 33.1 Errata ATmega48
- 33.2 Errata ATmega88
- 33.3 Errata ATmega168
34. Datasheet Revision History
- 34.1 Rev. 2545K-04/07
- 34.2 Rev. 2545J-12/06
- 34.3 Rev. 2545I-11/06
- 34.4 Rev. 2545H-10/06
- 34.5 Rev. 2545G-06/06
- 34.6 Rev. 2545F-05/05
- 34.7 Rev. 2545E-02/05
- 34.8 Rev. 2545D-07/04
- 34.9 Rev. 2545C-04/04
- 34.10 Rev. 2545B-01/04
Table of Contents

2545K–AVR–04/07

ATmega48/88/168

9.9 Register Description

9.9.1 MCUSR – MCU Status Register

The MCU Status Register provides information on which reset source caused an MCU reset.

• Bit 7..4: Res: Reserved Bits

These bits are unused bits in the ATmega48/88/168, and will always read as zero.

• Bit 3 – WDRF: Watchdog System Reset Flag

This bit is set if a Watchdog System Reset occurs. The bit is reset by a Power-on Reset, or by

writing a logic zero to the flag.

• Bit 2 – BORF: Brown-out Reset Flag

This bit is set if a Brown-out Reset occurs. The bit is reset by a Power-on Reset, or by writing a

logic zero to the flag.

• Bit 1 – EXTRF: External Reset Flag

This bit is set if an External Reset occurs. The bit is reset by a Power-on Reset, or by writing a

logic zero to the flag.

• Bit 0 – PORF: Power-on Reset Flag

This bit is set if a Power-on Reset occurs. The bit is reset only by writing a logic zero to the flag.

To make use of the Reset Flags to identify a reset condition, the user should read and then

Reset the MCUSR as early as possible in the program. If the register is cleared before another

reset occurs, the source of the reset can be found by examining the Reset Flags.

9.9.2 WDTCSR – Watchdog Timer Control Register

• Bit 7 - WDIF: Watchdog Interrupt Flag

This bit is set when a time-out occurs in the Watchdog Timer and the Watchdog Timer is config-

ured for interrupt. WDIF is cleared by hardware when executing the corresponding interrupt

handling vector. Alternatively, WDIF is cleared by writing a logic one to the flag. When the I-bit in

SREG and WDIE are set, the Watchdog Time-out Interrupt is executed.

• Bit 6 - WDIE: Watchdog Interrupt Enable

When this bit is written to one and the I-bit in the Status Register is set, the Watchdog Interrupt is

enabled. If WDE is cleared in combination with this setting, the Watchdog Timer is in Interrupt

Mode, and the corresponding interrupt is executed if time-out in the Watchdog Timer occurs.

Bit 76543210

0x35 (0x55) ––––WDRFBORFEXTRFPORFMCUSR

Read/Write RRRRR/WR/WR/WR/W

Initial Value0000 See Bit Description

Bit 76543210

(0x60) WDIF WDIE WDP3 WDCE WDE WDP2 WDP1 WDP0 WDTCSR

Read/Write R/W R/W R/W R/W R/W R/W R/W R/W

Initial Value 0 0 0 0 X 0 0 0