Datasheet

ManualsBrandsMICROCHIP TECHNOLOGY ManualsMicrocontrollers, Microprocessors & QuartzesEmbedded microcontroller TQFP 100 (14x14) 8-Bit 8 MHz I/O number 69

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Table Of Contents

Features
1. Pin Configurations
2. Overview
- 2.1 Block Diagram
- 2.2 Comparison between ATmega325, ATmega3250, ATmega645 and ATmega6450
- 2.3 Pin Descriptions
3. Resources
4. Data Retention
5. About Code Examples
6. Capacitive touch sensing
7. AVR CPU Core
- 7.1 Overview
- 7.2 Architectural Overview
- 7.3 ALU – Arithmetic Logic Unit
- 7.4 Status Register
  - 7.4.1 SREG – AVR Status Register
- 7.5 General Purpose Register File
  - 7.5.1 The X-register, Y-register, and Z-register
- 7.6 Stack Pointer
- 7.7 Instruction Execution Timing
- 7.8 Reset and Interrupt Handling
  - 7.8.1 Interrupt Response Time
8. AVR Memories
- 8.1 In-System Reprogrammable Flash Program Memory
- 8.2 SRAM Data Memory
  - 8.2.1 Data Memory Access Times
- 8.3 EEPROM Data Memory
- 8.4 I/O Memory
  - 8.4.1 General Purpose I/O Registers
- 8.5 Register Description
9. System Clock and Clock Options
- 9.1 Clock Systems and their Distribution
- 9.2 Clock Sources
  - 9.2.1 Default Clock Source
- 9.3 Crystal Oscillator
- 9.4 Low-frequency Crystal Oscillator
- 9.5 Calibrated Internal RC Oscillator
- 9.6 External Clock
- 9.7 Clock Output Buffer
- 9.8 Timer/Counter Oscillator
- 9.9 System Clock Prescaler
  - 9.9.1 Switching Time
- 9.10 Register Description
  - 9.10.1 OSCCAL – Oscillator Calibration Register
  - 9.10.2 CLKPR – Clock Prescale Register
10. Power Management and Sleep Modes
- 10.1 Sleep Modes
- 10.2 Idle Mode
- 10.3 ADC Noise Reduction Mode
- 10.4 Power-down Mode
- 10.5 Power-save Mode
- 10.6 Standby Mode
- 10.7 Power Reduction Register
- 10.8 Minimizing Power Consumption
- 10.9 Register Description
  - 10.9.1 SMCR – Sleep Mode Control Register
  - 10.9.2 PRR – Power Reduction Register
11. System Control and Reset
- 11.1 Resetting the AVR
- 11.2 Reset Sources
- 11.3 Power-on Reset
- 11.4 External Reset
- 11.5 Brown-out Detection
- 11.6 Watchdog Reset
- 11.7 Internal Voltage Reference
  - 11.7.1 Voltage Reference Enable Signals and Start-up Time
- 11.8 Watchdog Timer
- 11.9 Timed Sequences for Changing the Configuration of the Watchdog Timer
  - 11.9.1 Safety Level 1
  - 11.9.2 Safety Level 2
- 11.10 Register Description
  - 11.10.1 MCUSR – MCU Status Register
  - 11.10.2 WDTCR – Watchdog Timer Control Register
12. Interrupts
- 12.1 Interrupt Vectors in Atmel ATmega325/3250/645/6450
- 12.2 Moving Interrupts Between Application and Boot Space
- 12.3 Register Description
  - 12.3.1 MCUCR – MCU Control Register
13. External Interrupts
- 13.1 Pin Change Interrupt Timing
- 13.2 Register Description
14. I/O-Ports
- 14.1 Overview
- 14.2 Ports as General Digital I/O
- 14.3 Alternate Port Functions
- 14.4 Register Description
15. 8-bit Timer/Counter0 with PWM
- 15.1 Features
- 15.2 Overview
  - 15.2.1 Definitions
  - 15.2.2 Registers
- 15.3 Timer/Counter Clock Sources
- 15.4 Counter Unit
- 15.5 Output Compare Unit
- 15.6 Compare Match Output Unit
  - 15.6.1 Compare Output Mode and Waveform Generation
- 15.7 Modes of Operation
- 15.8 Timer/Counter Timing Diagrams
- 15.9 Register Description
16. Timer/Counter0 and Timer/Counter1 Prescalers
- 16.0.1 Internal Clock Source
- 16.0.2 Prescaler Reset
- 16.0.3 External Clock Source
- 16.1 Register Description
  - 16.1.1 GTCCR – General Timer/Counter Control Register
17. 16-bit Timer/Counter1
- 17.1 Features
- 17.2 Overview
- 17.3 Accessing 16-bit Registers
  - 17.3.1 Reusing the Temporary High Byte Register
- 17.4 Timer/Counter Clock Sources
- 17.5 Counter Unit
- 17.6 Input Capture Unit
- 17.7 Output Compare Units
- 17.8 Compare Match Output Unit
  - 17.8.1 Compare Output Mode and Waveform Generation
- 17.9 Modes of Operation
- 17.10 Timer/Counter Timing Diagrams
- 17.11 Register Description
18. 8-bit Timer/Counter2 with PWM and Asynchronous Operation
- 18.1 Features
- 18.2 Overview
  - 18.2.1 Registers
  - 18.2.2 Definitions
- 18.3 Timer/Counter Clock Sources
- 18.4 Counter Unit
- 18.5 Output Compare Unit
- 18.6 Compare Match Output Unit
  - 18.6.1 Compare Output Mode and Waveform Generation
- 18.7 Modes of Operation
- 18.8 Timer/Counter Timing Diagrams
- 18.9 Asynchronous Operation of Timer/Counter2
- 18.10 Timer/Counter Prescaler
- 18.11 Register Description
19. SPI – Serial Peripheral Interface
- 19.1 Features
- 19.2 Overview
- 19.3 SS Pin Functionality
  - 19.3.1 Slave Mode
  - 19.3.2 Master Mode
- 19.4 Data Modes
- 19.5 Register Description
20. USART0
- 20.1 Features
- 20.2 Overview
  - 20.2.1 AVR USART vs. AVR UART – Compatibility
- 20.3 Clock Generation
- 20.4 Frame Formats
  - 20.4.1 Parity Bit Calculation
- 20.5 USART Initialization
- 20.6 Data Transmission – The USART Transmitter
- 20.7 Data Reception – The USART Receiver
- 20.8 Asynchronous Data Reception
- 20.9 Multi-processor Communication Mode
  - 20.9.1 Using MPCMn
- 20.10 Examples of Baud Rate Setting
- 20.11 Register Description
21. USI – Universal Serial Interface
- 21.1 Overview
- 21.2 Functional Descriptions
- 21.3 Alternative USI Usage
- 21.4 Register Descriptions
22. Analog Comparator
- 22.1 Analog Comparator Multiplexed Input
- 22.2 Register Description
23. Analog to Digital Converter
- 23.1 Features
- 23.2 Operation
- 23.3 Starting a Conversion
- 23.4 Prescaling and Conversion Timing
- 23.5 Changing Channel or Reference Selection
  - 23.5.1 ADC Input Channels
  - 23.5.2 ADC Voltage Reference
- 23.6 ADC Noise Canceler
- 23.7 ADC Conversion Result
- 23.8 Register Description
24. JTAG Interface and On-chip Debug System
- 24.1 Features
- 24.2 Overview
- 24.3 TAP – Test Access Port
- 24.4 TAP Controller
- 24.5 Using the Boundary-scan Chain
- 24.6 Using the On-chip Debug System
- 24.7 On-chip Debug Specific JTAG Instructions
- 24.8 Using the JTAG Programming Capabilities
- 24.9 Bibliography
- 24.10 Register Description
  - 24.10.1 OCDR – On-chip Debug Register
25. IEEE 1149.1 (JTAG) Boundary-scan
- 25.1 Features
- 25.2 System Overview
- 25.3 Data Registers
- 25.4 Boundary-scan Specific JTAG Instructions
- 25.5 Boundary-scan Related Register in I/O Memory
  - 25.5.1 MCUCR – MCU Control Register
  - 25.5.2 MCUSR – MCU Status Register
- 25.6 Boundary-scan Chain
- 25.7 Boundary-scan Order
- 25.8 Boundary-scan Description Language Files
26. Boot Loader Support – Read-While-Write Self-Programming
- 26.1 Features
- 26.2 Overview
- 26.3 Application and Boot Loader Flash Sections
  - 26.3.1 Application Section
  - 26.3.2 BLS – Boot Loader Section
- 26.4 Read-While-Write and No Read-While-Write Flash Sections
  - 26.4.1 RWW – Read-While-Write Section
  - 26.4.2 NRWW – No Read-While-Write Section
- 26.5 Boot Loader Lock Bits
- 26.6 Entering the Boot Loader Program
- 26.7 Addressing the Flash During Self-Programming
- 26.8 Self-Programming the Flash
- 26.9 Register Description
  - 26.9.1 Store Program Memory Control and Status Register – SPMCSR
27. Memory Programming
- 27.1 Program And Data Memory Lock Bits
- 27.2 Fuse Bits
  - 27.2.1 Latching of Fuses
- 27.3 Signature Bytes
- 27.4 Calibration Byte
- 27.5 Parallel Programming Parameters, Pin Mapping, and Commands
  - 27.5.1 Signal Names
- 27.6 Parallel Programming
- 27.7 Serial Downloading
- 27.8 Programming via the JTAG Interface
28. Electrical Characteristics
- 28.1 Absolute Maximum Ratings*
- 28.2 DC Characteristics
- 28.3 Speed Grades
- 28.4 Clock Characteristics
- 28.5 System and Reset Characteristics
- 28.6 SPI Timing Characteristics
- 28.7 ADC
29. Typical Characteristics
- 29.1 Active Supply Current
- 29.2 Idle Supply Current
- 29.3 Supply Current of I/O modules
- 29.4 Power-down Supply Current
- 29.5 Power-save Supply Current
- 29.6 Standby Supply Current
- 29.7 Pin Pull-up
- 29.8 Pin Driver Strength
- 29.9 Pin Thresholds and hysteresis
- 29.10 BOD Thresholds and Analog Comparator Offset
- 29.11 Internal Oscillator Speed
- 29.12 Current Consumption of Peripheral Units
- 29.13 Current Consumption in Reset and Reset Pulsewidth
30. Register Summary
31. Instruction Set Summary
32. Ordering Information
- 32.1 ATmega325
- 32.2 ATmega3250
- 32.3 ATmega645
- 32.4 ATmega6450
33. Packaging Information
- 33.1 64A
- 33.2 64M1
- 33.3 100A
34. Errata
- 34.1 Errata ATmega325
- 34.2 Errata ATmega3250
- 34.3 Errata ATmega645
  - 34.3.1 ATmega645 Rev. A
- 34.4 Errata ATmega6450
  - 34.4.1 ATmega6450 Rev. A
35. Datasheet Revision History
- 35.1 Rev. 2570N – 05/11
- 35.2 Rev. 2570M – 04/11
- 35.3 Rev. 2570L – 08/07
- 35.4 Rev. 2570K – 04/07
- 35.5 Rev. 2570J – 11/06
- 35.6 Rev. 2570I – 07/06
- 35.7 Rev. 2570H – 06/06
- 35.8 Rev. 2570G – 04/06
- 35.9 Rev. 2570F – 03/06
- 35.10 Rev. 2570E – 03/06
- 35.11 Rev. 2570D – 05/05
- 35.12 Rev. 2570C – 11/04
- 35.13 Rev. 2570B – 09/04
- 35.14 Rev. 2570A – 09/04
Table of Contents

157

2570N–AVR–05/11

ATmega325/3250/645/6450

20. USART0

20.1 Features

The Universal Synchronous and Asynchronous serial Receiver and Transmitter (USART) is a

highly flexible serial communication device. The main features are:

•

Full Duplex Operation (Independent Serial Receive and Transmit Registers)

• Asynchronous or Synchronous Operation

• Master or Slave Clocked Synchronous Operation

• High Resolution Baud Rate Generator

• Supports Serial Frames with 5, 6, 7, 8, or 9 Data Bits and 1 or 2 Stop Bits

• Odd or Even Parity Generation and Parity Check Supported by Hardware

• Data OverRun Detection

• Framing Error Detection

• Noise Filtering Includes False Start Bit Detection and Digital Low Pass Filter

• Three Separate Interrupts on TX Complete, TX Data Register Empty and RX Complete

• Multi-processor Communication Mode

• Double Speed Asynchronous Communication Mode

20.2 Overview

A simplified block diagram of the USART Transmitter is shown in Figure 20-1. CPU accessible

I/O Registers and I/O pins are shown in bold.

The Power Reduction USART bit, PRUSART0, in “Power Reduction Register” on page 37 must

be written to zero to enable the USART0 module.