Datasheet ATtiny43U (Atmel) - 10
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4.5. General Purpose Register File. Figure 4-2. 4.5.1. The X-register, Y-register, and Z-register. ATtiny43U
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4.5 General Purpose Register File
The Register File is optimized for the AVR Enhanced RISC instruction set. In order to achieve the required performance and flexibility, the following input/output schemes are supported by the Register File: • One 8-bit output operand and one 8-bit result input • Two 8-bit output operands and one 8-bit result input • Two 8-bit output operands and one 16-bit result input • One 16-bit output operand and one 16-bit result input Figure 4-2 on page 10 shows the structure of the 32 general purpose working registers in the CPU.
Figure 4-2.
AVR CPU General Purpose Working Registers 7 0 Addr. R0 0x00 R1 0x01 R2 0x02 … R13 0x0D General R14 0x0E Purpose R15 0x0F Working R16 0x10 Registers R17 0x11 … R26 0x1A X-register Low Byte R27 0x1B X-register High Byte R28 0x1C Y-register Low Byte R29 0x1D Y-register High Byte R30 0x1E Z-register Low Byte R31 0x1F Z-register High Byte Most of the instructions operating on the Register File have direct access to all registers, and most of them are single cycle instructions. As shown in Figure 4-2, each register is also assigned a Data memory address, mapping them directly into the first 32 locations of the user Data Space. Although not being physically imple- mented as SRAM locations, this memory organization provides great flexibility in access of the registers, as the X-, Y- and Z-pointer registers can be set to index any register in the file.
4.5.1 The X-register, Y-register, and Z-register
The registers R26..R31 have some added functions to their general purpose usage. These reg- isters are 16-bit address pointers for indirect addressing of the data space. The three indirect address registers X, Y, and Z are defined as described in Figure 4-3 on page 11.
10 ATtiny43U
8048C–AVR–02/12 Document Outline Features 1. Pin Configurations 1.1 Pin Descriptions 1.1.1 VCC 1.1.2 GND 1.1.3 Port A (PA7:PA0) 1.1.4 RESET 1.1.5 Port B (PB7:PB0) 1.1.6 LSW 1.1.7 VBAT 2. Overview 3. General Information 3.1 Resources 3.2 Code Examples 3.3 Capacitive Touch Sensing 3.4 Data Retention 4. AVR CPU Core 4.1 Introduction 4.2 Architectural Overview 4.3 ALU – Arithmetic Logic Unit 4.4 Status Register 4.4.1 SREG - AVR Status Register 4.5 General Purpose Register File 4.5.1 The X-register, Y-register, and Z-register 4.6 Stack Pointer 4.6.1 SPH and SPL — Stack Pointer Register 4.7 Instruction Execution Timing 4.8 Reset and Interrupt Handling 4.8.1 Interrupt Response Time 5. Memories 5.1 In-System Re-programmable Flash Program Memory 5.2 SRAM Data Memory 5.2.1 Data Memory Access Times 5.3 EEPROM Data Memory 5.3.1 EEPROM Read/Write Access 5.3.2 Atomic Byte Programming 5.3.3 Split Byte Programming 5.3.4 Erase 5.3.5 Write 5.3.6 Preventing EEPROM Corruption 5.4 I/O Memory 5.4.1 General Purpose I/O Registers 5.5 Register Description 5.5.1 EEAR – EEPROM Address Register 5.5.2 EEDR – EEPROM Data Register 5.5.3 EECR – EEPROM Control Register 5.5.4 GPIOR2 – General Purpose I/O Register 2 5.5.5 GPIOR1 – General Purpose I/O Register 1 5.5.6 GPIOR0 – General Purpose I/O Register 0 6. System Clock and Clock Options 6.1 Clock Systems and their Distribution 6.1.1 CPU Clock – clkCPU 6.1.2 I/O Clock – clkI/O 6.1.3 Flash Clock – clkFLASH 6.1.4 ADC Clock – clkADC 6.2 Clock Sources 6.2.1 External Clock 6.2.2 Calibrated Internal 8 MHz Oscillator 6.2.3 Internal 128 kHz Oscillator 6.2.4 Default Clock Source 6.2.5 Clock Startup Sequence 6.3 System Clock Prescaler 6.3.1 Switching Time 6.4 Clock Output Buffer 6.5 Register Description 6.5.1 OSCCAL – Oscillator Calibration Register 6.5.2 CLKPR – Clock Prescale Register 7. Power Management and Sleep Modes 7.1 Sleep Modes 7.1.1 Idle Mode 7.1.2 ADC Noise Reduction Mode 7.1.3 Power-Down Mode 7.2 Software BOD Disable 7.3 Power Reduction Register 7.4 Minimizing Power Consumption 7.4.1 Analog to Digital Converter 7.4.2 Analog Comparator 7.4.3 Brown-out Detector 7.4.4 Internal Voltage Reference 7.4.5 Watchdog Timer 7.4.6 Port Pins 7.5 Register Description 7.5.1 MCUCR – MCU Control Register 7.5.2 PRR – Power Reduction Register 8. Power Supply and On-Chip Boost Converter 8.1 Overview 8.2 Modes of Operation 8.2.1 Stop Mode 8.2.2 Start Mode 8.2.3 Active Mode 8.2.4 Examples 8.3 Output Voltage versus Load Current 8.3.1 Active Regulated Mode 8.3.2 Active Low Current Mode 8.3.3 Full Duty Cycle 8.4 Overload Behaviour 8.5 Software Control of Boost Converter 8.5.1 Stopping the Boost Converter 8.5.2 Switching to Full Duty Cycle Mode of Operation 8.5.3 Switching to Normal (Variable Duty Cycle) Mode of Operation 8.6 Component Selection 8.6.1 Inductor 8.6.2 Diode 8.6.3 Input Capacitors 8.6.4 RC Filter 8.6.5 Output Capacitors 8.6.6 Summary 8.7 Characteristics 8.8 Potential Limitations 8.9 Bypassing the Boost Converter 8.10 Firmware Example 8.11 Register Description 8.11.1 ADCSRB – ADC Control and Status Register B 9. System Control and Reset 9.1 Resetting the AVR 9.2 Reset Sources 9.2.1 Power-on Reset 9.2.2 External Reset 9.2.3 Brown-out Detection 9.2.4 Watchdog Reset 9.3 Internal Voltage Reference 9.3.1 Voltage Reference Enable Signals and Start-up Time 9.4 Watchdog Timer 9.4.1 Timed Sequences for Changing the Configuration of the Watchdog Timer 9.4.1.1 Safety Level 1 9.4.1.2 Safety Level 2 9.4.2 Code Example 9.5 Register Description 9.5.1 MCUSR – MCU Status Register 9.5.2 WDTCSR – Watchdog Timer Control and Status Register 10. Interrupts 10.1 Interrupt Vectors 10.2 External Interrupts 10.2.1 Pin Change Interrupt Timing 10.3 Register Description 10.3.1 MCUCR – MCU Control Register 10.3.2 GIMSK – General Interrupt Mask Register 10.3.3 GIFR – General Interrupt Flag Register 10.3.4 PCMSK1 – Pin Change Mask Register 1 10.3.5 PCMSK0 – Pin Change Mask Register 0 11. I/O Ports 11.1 Introduction 11.2 Ports as General Digital I/O 11.2.1 Configuring the Pin 11.2.2 Toggling the Pin 11.2.3 Switching Between Input and Output 11.2.4 Reading the Pin Value 11.2.5 Digital Input Enable and Sleep Modes 11.2.6 Unconnected Pins 11.3 Alternate Port Functions 11.3.1 Alternate Functions of Port A 11.3.2 Alternate Functions of Port B 11.4 Register Description 11.4.1 MCUCR – MCU Control Register 11.4.2 PORTA – Port A Data Register 11.4.3 DDRA – Port A Data Direction Register 11.4.4 PINA – Port A Input Pins Address 11.4.5 PORTB – Port B Data Register 11.4.6 DDRB – Port B Data Direction Register 11.4.7 PINB – Port BInput Pins Address 12. 8-bit Timer/Counter with PWM (Timer/Counter0 and Timer/Counter1) 12.1 Features 12.2 Overview 12.2.1 Registers 12.2.2 Definitions 12.3 Timer/Counter Clock Sources 12.4 Counter Unit 12.5 Output Compare Unit 12.5.1 Force Output Compare 12.5.2 Compare Match Blocking by TCNTn Write 12.5.3 Using the Output Compare Unit 12.6 Compare Match Output Unit 12.6.1 Compare Output Mode and Waveform Generation 12.7 Modes of Operation 12.7.1 Normal Mode 12.7.2 Clear Timer on Compare Match (CTC) Mode 12.7.3 Fast PWM Mode 12.7.4 Phase Correct PWM Mode 12.8 Timer/Counter Timing Diagrams 12.9 Register Description 12.9.1 TCCR0A – Timer/Counter Control Register A 12.9.2 TCCR1A – Timer/Counter Control Register A 12.9.3 TCCR0B – Timer/Counter Control Register B 12.9.4 TCCR1B – Timer/Counter Control Register B 12.9.5 TCNT0 – Timer/Counter Register 12.9.6 TCNT1 – Timer/Counter Register 12.9.7 OCR0A – Output Compare Register A 12.9.8 OCR1A – Output Compare Register A 12.9.9 OCR0B – Output Compare Register B 12.9.10 OCR1B – Output Compare Register B 12.9.11 TIMSK0 – Timer/Counter 0 Interrupt Mask Register 12.9.12 TIMSK1 – Timer/Counter 1 Interrupt Mask Register 12.9.13 TIFR0 – Timer/Counter 0 Interrupt Flag Register 12.9.14 TIFR1 – Timer/Counter 1 Interrupt Flag Register 13. Timer/Counter Prescaler 13.1 Prescaler Reset 13.2 External Clock Source 13.3 Register Description 13.3.1 GTCCR – General Timer/Counter Control Register 14. USI – Universal Serial Interface 14.1 Features 14.2 Overview 14.3 Functional Descriptions 14.3.1 Three-wire Mode 14.3.2 SPI Master Operation Example 14.3.3 SPI Slave Operation Example 14.3.4 Two-wire Mode 14.3.5 Start Condition Detector 14.4 Alternative USI Usage 14.4.1 Half-Duplex Asynchronous Data Transfer 14.4.2 4-Bit Counter 14.4.3 12-Bit Timer/Counter 14.4.4 Edge Triggered External Interrupt 14.4.5 Software Interrupt 14.5 Register Descriptions 14.5.1 USICR – USI Control Register 14.5.2 USISR – USI Status Register 14.5.3 USIDR – USI Data Register 14.5.4 USIBR – USI Buffer Register 15. Analog Comparator 15.1 Analog Comparator Multiplexed Input 15.2 Register Description 15.2.1 ADCSRB – ADC Control and Status Register B 15.2.2 ACSR – Analog Comparator Control and Status Register 15.2.3 DIDR0 – Digital Input Disable Register 0 16. Analog to Digital Converter 16.1 Features 16.2 Overview 16.3 ADC Operation 16.4 Starting a Conversion 16.5 Prescaling and Conversion Timing 16.6 Changing Channel or Reference Selection 16.6.1 ADC Input Channels 16.6.2 ADC Voltage Reference 16.7 ADC Noise Canceler 16.8 Analog Input Circuitry 16.9 Analog Noise Canceling Techniques 16.10 ADC Accuracy Definitions 16.11 ADC Conversion Result 16.12 Temperature Measurement 16.13 Register Description 16.13.1 ADMUX – ADC Multiplexer Selection Register 16.13.2 ADCSRA – ADC Control and Status Register A 16.13.3 ADCL and ADCH – ADC Data Register 16.13.3.1 ADLAR = 0 16.13.3.2 ADLAR = 1 16.13.4 ADCSRB – ADC Control and Status Register B 16.13.5 DIDR0 – Digital Input Disable Register 0 17. debugWIRE On-chip Debug System 17.1 Features 17.2 Overview 17.3 Physical Interface 17.4 Software Break Points 17.5 Limitations of debugWIRE 17.6 Register Description 17.6.1 DWDR – debugWire Data Register 18. Self-Programming the Flash 18.1 Performing Page Erase by SPM 18.2 Filling the Temporary Buffer (Page Loading) 18.3 Performing a Page Write 18.4 Addressing the Flash During Self-Programming 18.5 EEPROM Write Prevents Writing to SPMCSR 18.6 Reading the Fuse and Lock Bits from Software 18.6.1 Reading Lock Bits from Firmware 18.6.2 Reading Fuse Bits from Firmware 18.6.3 Reading Device Signature Imprint Table from Firmware 18.7 Preventing Flash Corruption 18.8 Programming Time for Flash when Using SPM 18.9 Register Description 18.9.1 SPMCSR – Store Program Memory Control and Status Register 19. Memory Programming 19.1 Program And Data Memory Lock Bits 19.2 Fuse Bytes 19.2.1 Latching of Fuses 19.3 Device Signature Imprint Table 19.3.1 Signature Bytes 19.3.2 Calibration Byte 19.4 Page Size 19.5 Parallel Programming Parameters, Pin Mapping, and Commands 19.5.1 Signal Names 19.6 Parallel Programming 19.6.1 Enter Programming Mode 19.6.2 Considerations for Efficient Programming 19.6.3 Chip Erase 19.6.4 Programming the Flash 19.6.5 Programming the EEPROM 19.6.6 Reading the Flash 19.6.7 Reading the EEPROM 19.6.8 Programming the Fuse Low Bits 19.6.9 Programming the Fuse High Bits 19.6.10 Programming the Extended Fuse Bits 19.6.11 Programming the Lock Bits 19.6.12 Reading the Fuse and Lock Bits 19.6.13 Reading the Signature Bytes 19.6.14 Reading the Calibration Byte 19.7 Serial Programming 19.7.1 Serial Programming Algorithm 19.7.2 Serial Programming Instruction set 20. Electrical Characteristics 20.1 Absolute Maximum Ratings* 20.2 DC Characteristics 20.3 Speed 20.4 Clock Characteristics 20.4.1 Calibrated Internal Oscillator Accuracy 20.4.2 External Clock Drive 20.5 System and Reset Characteristics 20.6 External Interrupt Characteristics 20.7 Boost Converter Characteristics 20.8 ADC Characteristics 20.9 Parallel Programming Characteristics 20.10 Serial Programming Characteristics 21. Typical Characteristics 21.1 Boost Converter 21.2 Current Consumption in Active Mode 21.3 Current Consumption in Idle Mode 21.4 Current Consumption in Power-down Mode 21.5 Current Consumption in Reset 21.6 Current Consumption of Peripheral Units 21.7 Pull-up Resistors 21.8 Output Driver Strength 21.9 Input Thresholds and Hysteresis (for I/O Ports) 21.10 BOD, Bandgap and Reset 21.11 Internal Oscillators 22. Register Summary 23. Instruction Set Summary 24. Ordering Information 24.1 ATtiny43U 25. Packaging Information 25.1 20M1 25.2 20S2 26. Errata 26.1 ATtiny43U 26.1.1 Rev. D – F 26.1.2 Rev. C 26.1.3 Rev. B – A 27. Datasheet Revision History 27.1 Rev. 8048C – 02/12 27.2 Rev. 8048B – 05/09 27.3 Rev. 8048A – 02/09 Table of Contents
4.5 General Purpose Register File
The Register File is optimized for the AVR Enhanced RISC instruction set. In order to achieve the required performance and flexibility, the following input/output schemes are supported by the Register File: • One 8-bit output operand and one 8-bit result input • Two 8-bit output operands and one 8-bit result input • Two 8-bit output operands and one 16-bit result input • One 16-bit output operand and one 16-bit result input Figure 4-2 on page 10 shows the structure of the 32 general purpose working registers in the CPU.
Figure 4-2.
AVR CPU General Purpose Working Registers 7 0 Addr. R0 0x00 R1 0x01 R2 0x02 … R13 0x0D General R14 0x0E Purpose R15 0x0F Working R16 0x10 Registers R17 0x11 … R26 0x1A X-register Low Byte R27 0x1B X-register High Byte R28 0x1C Y-register Low Byte R29 0x1D Y-register High Byte R30 0x1E Z-register Low Byte R31 0x1F Z-register High Byte Most of the instructions operating on the Register File have direct access to all registers, and most of them are single cycle instructions. As shown in Figure 4-2, each register is also assigned a Data memory address, mapping them directly into the first 32 locations of the user Data Space. Although not being physically imple- mented as SRAM locations, this memory organization provides great flexibility in access of the registers, as the X-, Y- and Z-pointer registers can be set to index any register in the file.
4.5.1 The X-register, Y-register, and Z-register
The registers R26..R31 have some added functions to their general purpose usage. These reg- isters are 16-bit address pointers for indirect addressing of the data space. The three indirect address registers X, Y, and Z are defined as described in Figure 4-3 on page 11.
10 ATtiny43U
8048C–AVR–02/12 Document Outline Features 1. Pin Configurations 1.1 Pin Descriptions 1.1.1 VCC 1.1.2 GND 1.1.3 Port A (PA7:PA0) 1.1.4 RESET 1.1.5 Port B (PB7:PB0) 1.1.6 LSW 1.1.7 VBAT 2. Overview 3. General Information 3.1 Resources 3.2 Code Examples 3.3 Capacitive Touch Sensing 3.4 Data Retention 4. AVR CPU Core 4.1 Introduction 4.2 Architectural Overview 4.3 ALU – Arithmetic Logic Unit 4.4 Status Register 4.4.1 SREG - AVR Status Register 4.5 General Purpose Register File 4.5.1 The X-register, Y-register, and Z-register 4.6 Stack Pointer 4.6.1 SPH and SPL — Stack Pointer Register 4.7 Instruction Execution Timing 4.8 Reset and Interrupt Handling 4.8.1 Interrupt Response Time 5. Memories 5.1 In-System Re-programmable Flash Program Memory 5.2 SRAM Data Memory 5.2.1 Data Memory Access Times 5.3 EEPROM Data Memory 5.3.1 EEPROM Read/Write Access 5.3.2 Atomic Byte Programming 5.3.3 Split Byte Programming 5.3.4 Erase 5.3.5 Write 5.3.6 Preventing EEPROM Corruption 5.4 I/O Memory 5.4.1 General Purpose I/O Registers 5.5 Register Description 5.5.1 EEAR – EEPROM Address Register 5.5.2 EEDR – EEPROM Data Register 5.5.3 EECR – EEPROM Control Register 5.5.4 GPIOR2 – General Purpose I/O Register 2 5.5.5 GPIOR1 – General Purpose I/O Register 1 5.5.6 GPIOR0 – General Purpose I/O Register 0 6. System Clock and Clock Options 6.1 Clock Systems and their Distribution 6.1.1 CPU Clock – clkCPU 6.1.2 I/O Clock – clkI/O 6.1.3 Flash Clock – clkFLASH 6.1.4 ADC Clock – clkADC 6.2 Clock Sources 6.2.1 External Clock 6.2.2 Calibrated Internal 8 MHz Oscillator 6.2.3 Internal 128 kHz Oscillator 6.2.4 Default Clock Source 6.2.5 Clock Startup Sequence 6.3 System Clock Prescaler 6.3.1 Switching Time 6.4 Clock Output Buffer 6.5 Register Description 6.5.1 OSCCAL – Oscillator Calibration Register 6.5.2 CLKPR – Clock Prescale Register 7. Power Management and Sleep Modes 7.1 Sleep Modes 7.1.1 Idle Mode 7.1.2 ADC Noise Reduction Mode 7.1.3 Power-Down Mode 7.2 Software BOD Disable 7.3 Power Reduction Register 7.4 Minimizing Power Consumption 7.4.1 Analog to Digital Converter 7.4.2 Analog Comparator 7.4.3 Brown-out Detector 7.4.4 Internal Voltage Reference 7.4.5 Watchdog Timer 7.4.6 Port Pins 7.5 Register Description 7.5.1 MCUCR – MCU Control Register 7.5.2 PRR – Power Reduction Register 8. Power Supply and On-Chip Boost Converter 8.1 Overview 8.2 Modes of Operation 8.2.1 Stop Mode 8.2.2 Start Mode 8.2.3 Active Mode 8.2.4 Examples 8.3 Output Voltage versus Load Current 8.3.1 Active Regulated Mode 8.3.2 Active Low Current Mode 8.3.3 Full Duty Cycle 8.4 Overload Behaviour 8.5 Software Control of Boost Converter 8.5.1 Stopping the Boost Converter 8.5.2 Switching to Full Duty Cycle Mode of Operation 8.5.3 Switching to Normal (Variable Duty Cycle) Mode of Operation 8.6 Component Selection 8.6.1 Inductor 8.6.2 Diode 8.6.3 Input Capacitors 8.6.4 RC Filter 8.6.5 Output Capacitors 8.6.6 Summary 8.7 Characteristics 8.8 Potential Limitations 8.9 Bypassing the Boost Converter 8.10 Firmware Example 8.11 Register Description 8.11.1 ADCSRB – ADC Control and Status Register B 9. System Control and Reset 9.1 Resetting the AVR 9.2 Reset Sources 9.2.1 Power-on Reset 9.2.2 External Reset 9.2.3 Brown-out Detection 9.2.4 Watchdog Reset 9.3 Internal Voltage Reference 9.3.1 Voltage Reference Enable Signals and Start-up Time 9.4 Watchdog Timer 9.4.1 Timed Sequences for Changing the Configuration of the Watchdog Timer 9.4.1.1 Safety Level 1 9.4.1.2 Safety Level 2 9.4.2 Code Example 9.5 Register Description 9.5.1 MCUSR – MCU Status Register 9.5.2 WDTCSR – Watchdog Timer Control and Status Register 10. Interrupts 10.1 Interrupt Vectors 10.2 External Interrupts 10.2.1 Pin Change Interrupt Timing 10.3 Register Description 10.3.1 MCUCR – MCU Control Register 10.3.2 GIMSK – General Interrupt Mask Register 10.3.3 GIFR – General Interrupt Flag Register 10.3.4 PCMSK1 – Pin Change Mask Register 1 10.3.5 PCMSK0 – Pin Change Mask Register 0 11. I/O Ports 11.1 Introduction 11.2 Ports as General Digital I/O 11.2.1 Configuring the Pin 11.2.2 Toggling the Pin 11.2.3 Switching Between Input and Output 11.2.4 Reading the Pin Value 11.2.5 Digital Input Enable and Sleep Modes 11.2.6 Unconnected Pins 11.3 Alternate Port Functions 11.3.1 Alternate Functions of Port A 11.3.2 Alternate Functions of Port B 11.4 Register Description 11.4.1 MCUCR – MCU Control Register 11.4.2 PORTA – Port A Data Register 11.4.3 DDRA – Port A Data Direction Register 11.4.4 PINA – Port A Input Pins Address 11.4.5 PORTB – Port B Data Register 11.4.6 DDRB – Port B Data Direction Register 11.4.7 PINB – Port BInput Pins Address 12. 8-bit Timer/Counter with PWM (Timer/Counter0 and Timer/Counter1) 12.1 Features 12.2 Overview 12.2.1 Registers 12.2.2 Definitions 12.3 Timer/Counter Clock Sources 12.4 Counter Unit 12.5 Output Compare Unit 12.5.1 Force Output Compare 12.5.2 Compare Match Blocking by TCNTn Write 12.5.3 Using the Output Compare Unit 12.6 Compare Match Output Unit 12.6.1 Compare Output Mode and Waveform Generation 12.7 Modes of Operation 12.7.1 Normal Mode 12.7.2 Clear Timer on Compare Match (CTC) Mode 12.7.3 Fast PWM Mode 12.7.4 Phase Correct PWM Mode 12.8 Timer/Counter Timing Diagrams 12.9 Register Description 12.9.1 TCCR0A – Timer/Counter Control Register A 12.9.2 TCCR1A – Timer/Counter Control Register A 12.9.3 TCCR0B – Timer/Counter Control Register B 12.9.4 TCCR1B – Timer/Counter Control Register B 12.9.5 TCNT0 – Timer/Counter Register 12.9.6 TCNT1 – Timer/Counter Register 12.9.7 OCR0A – Output Compare Register A 12.9.8 OCR1A – Output Compare Register A 12.9.9 OCR0B – Output Compare Register B 12.9.10 OCR1B – Output Compare Register B 12.9.11 TIMSK0 – Timer/Counter 0 Interrupt Mask Register 12.9.12 TIMSK1 – Timer/Counter 1 Interrupt Mask Register 12.9.13 TIFR0 – Timer/Counter 0 Interrupt Flag Register 12.9.14 TIFR1 – Timer/Counter 1 Interrupt Flag Register 13. Timer/Counter Prescaler 13.1 Prescaler Reset 13.2 External Clock Source 13.3 Register Description 13.3.1 GTCCR – General Timer/Counter Control Register 14. USI – Universal Serial Interface 14.1 Features 14.2 Overview 14.3 Functional Descriptions 14.3.1 Three-wire Mode 14.3.2 SPI Master Operation Example 14.3.3 SPI Slave Operation Example 14.3.4 Two-wire Mode 14.3.5 Start Condition Detector 14.4 Alternative USI Usage 14.4.1 Half-Duplex Asynchronous Data Transfer 14.4.2 4-Bit Counter 14.4.3 12-Bit Timer/Counter 14.4.4 Edge Triggered External Interrupt 14.4.5 Software Interrupt 14.5 Register Descriptions 14.5.1 USICR – USI Control Register 14.5.2 USISR – USI Status Register 14.5.3 USIDR – USI Data Register 14.5.4 USIBR – USI Buffer Register 15. Analog Comparator 15.1 Analog Comparator Multiplexed Input 15.2 Register Description 15.2.1 ADCSRB – ADC Control and Status Register B 15.2.2 ACSR – Analog Comparator Control and Status Register 15.2.3 DIDR0 – Digital Input Disable Register 0 16. Analog to Digital Converter 16.1 Features 16.2 Overview 16.3 ADC Operation 16.4 Starting a Conversion 16.5 Prescaling and Conversion Timing 16.6 Changing Channel or Reference Selection 16.6.1 ADC Input Channels 16.6.2 ADC Voltage Reference 16.7 ADC Noise Canceler 16.8 Analog Input Circuitry 16.9 Analog Noise Canceling Techniques 16.10 ADC Accuracy Definitions 16.11 ADC Conversion Result 16.12 Temperature Measurement 16.13 Register Description 16.13.1 ADMUX – ADC Multiplexer Selection Register 16.13.2 ADCSRA – ADC Control and Status Register A 16.13.3 ADCL and ADCH – ADC Data Register 16.13.3.1 ADLAR = 0 16.13.3.2 ADLAR = 1 16.13.4 ADCSRB – ADC Control and Status Register B 16.13.5 DIDR0 – Digital Input Disable Register 0 17. debugWIRE On-chip Debug System 17.1 Features 17.2 Overview 17.3 Physical Interface 17.4 Software Break Points 17.5 Limitations of debugWIRE 17.6 Register Description 17.6.1 DWDR – debugWire Data Register 18. Self-Programming the Flash 18.1 Performing Page Erase by SPM 18.2 Filling the Temporary Buffer (Page Loading) 18.3 Performing a Page Write 18.4 Addressing the Flash During Self-Programming 18.5 EEPROM Write Prevents Writing to SPMCSR 18.6 Reading the Fuse and Lock Bits from Software 18.6.1 Reading Lock Bits from Firmware 18.6.2 Reading Fuse Bits from Firmware 18.6.3 Reading Device Signature Imprint Table from Firmware 18.7 Preventing Flash Corruption 18.8 Programming Time for Flash when Using SPM 18.9 Register Description 18.9.1 SPMCSR – Store Program Memory Control and Status Register 19. Memory Programming 19.1 Program And Data Memory Lock Bits 19.2 Fuse Bytes 19.2.1 Latching of Fuses 19.3 Device Signature Imprint Table 19.3.1 Signature Bytes 19.3.2 Calibration Byte 19.4 Page Size 19.5 Parallel Programming Parameters, Pin Mapping, and Commands 19.5.1 Signal Names 19.6 Parallel Programming 19.6.1 Enter Programming Mode 19.6.2 Considerations for Efficient Programming 19.6.3 Chip Erase 19.6.4 Programming the Flash 19.6.5 Programming the EEPROM 19.6.6 Reading the Flash 19.6.7 Reading the EEPROM 19.6.8 Programming the Fuse Low Bits 19.6.9 Programming the Fuse High Bits 19.6.10 Programming the Extended Fuse Bits 19.6.11 Programming the Lock Bits 19.6.12 Reading the Fuse and Lock Bits 19.6.13 Reading the Signature Bytes 19.6.14 Reading the Calibration Byte 19.7 Serial Programming 19.7.1 Serial Programming Algorithm 19.7.2 Serial Programming Instruction set 20. Electrical Characteristics 20.1 Absolute Maximum Ratings* 20.2 DC Characteristics 20.3 Speed 20.4 Clock Characteristics 20.4.1 Calibrated Internal Oscillator Accuracy 20.4.2 External Clock Drive 20.5 System and Reset Characteristics 20.6 External Interrupt Characteristics 20.7 Boost Converter Characteristics 20.8 ADC Characteristics 20.9 Parallel Programming Characteristics 20.10 Serial Programming Characteristics 21. Typical Characteristics 21.1 Boost Converter 21.2 Current Consumption in Active Mode 21.3 Current Consumption in Idle Mode 21.4 Current Consumption in Power-down Mode 21.5 Current Consumption in Reset 21.6 Current Consumption of Peripheral Units 21.7 Pull-up Resistors 21.8 Output Driver Strength 21.9 Input Thresholds and Hysteresis (for I/O Ports) 21.10 BOD, Bandgap and Reset 21.11 Internal Oscillators 22. Register Summary 23. Instruction Set Summary 24. Ordering Information 24.1 ATtiny43U 25. Packaging Information 25.1 20M1 25.2 20S2 26. Errata 26.1 ATtiny43U 26.1.1 Rev. D – F 26.1.2 Rev. C 26.1.3 Rev. B – A 27. Datasheet Revision History 27.1 Rev. 8048C – 02/12 27.2 Rev. 8048B – 05/09 27.3 Rev. 8048A – 02/09 Table of Contents