Datasheet ATmega161, ATmega161L (Atmel) - 8

In addition to the register operation, the conventional Memory Addressing modes can be used on the Register File. This is enabled by the fact that the Register File is assigned the 32 lowermost Data Space addresses ($00 - $1F), allowing them to be accessed as though they were ordinary memory locations. The I/O memory space contains 64 addresses for CPU peripheral functions such as Control Registers, Timer/Counters, and other I/O functions. The I/O memory can be accessed directly or as the Data Space locations following those of the Register File, $20 - $5F. The AVR uses a Harvard architecture concept – with separate memories and buses for program and data. The Program memory is executed with a two-stage pipeline. While one instruction is being executed, the next instruction is pre-fetched from the Program memory. This concept enables instructions to be executed in every clock cycle. The Program memory is Self-programmable Flash memory. With the jump and call instructions, the whole 8K word address space is directly accessed. Most AVR instructions have a single 16-bit word format. Every Program memory address contains a 16- or 32-bit instruction. During interrupts and subroutine calls, the return address Program Counter (PC) is stored on the Stack. The Stack is effectively allocated in the general data SRAM and, consequently, the Stack size is only limited by the total SRAM size and the usage of the SRAM. All user programs must initialize the SP (Stack Pointer) in the reset routine (before subroutines or interrupts are executed). The 16-bit Stack Pointer is read/write accessible in the I/O space. The 1K byte data SRAM can be easily accessed through the five different Addressing modes supported in the AVR architecture. The memory spaces in the AVR architecture are all linear and regular memory maps.
8 ATmega161(L)
1228D–AVR–02/07 Document Outline Features Disclaimer Pin Configuration Description Block Diagram Pin Descriptions VCC GND Port A (PA7..PA0) Port B (PB7..PB0) Port C (PC7..PC0) Port D (PD7..PD0) Port E (PE2..PE0) RESET XTAL1 XTAL2 Crystal Oscillator Architectural Overview The General Purpose Register File The X-register, Y-register and Z-register ALU - Arithmetic Logic Unit Self-programmable Flash Program Memory EEPROM Data Memory SRAM Data Memory Program and Data Addressing Modes Register Direct, Single Register Rd Register Direct, Two Registers Rd and Rr I/O Direct Data Direct Data Indirect with Displacement Data Indirect Data Indirect with Pre- decrement Data Indirect with Post- increment Constant Addressing Using the LPM Instruction Indirect Program Addressing, IJMP and ICALL Relative Program Addressing, RJMP and RCALL Direct Program Addressing, JMP and CALL Memory Access Times and Instruction Execution Timing l/O Memory Status Register - SREG Stack Pointer - SP Reset and Interrupt Handling Reset Sources Power-on Reset External Reset Watchdog Reset MCU Status Register - MCUSR Interrupt Handling Interrupt Response Time General Interrupt Mask Register - GIMSK General Interrupt Flag Register - GIFR Timer/Counter Interrupt Mask Register - TIMSK Timer/Counter Interrupt Flag Register - TIFR External Interrupts MCU Control Register - MCUCR Extended MCU Control Register - EMCUCR Sleep Modes Idle Mode Power-down Mode Power-save Mode Timer/Counters Timer/Counter Prescalers Special Function IO Register - SFIOR 8-bit Timer/Counters T/C0 and T/C2 Timer/Counter0 Control Register - TCCR0 Timer/Counter2 Control Register - TCCR2 Timer Counter0 - TCNT0 Timer/Counter2 - TCNT2 Timer/Counter0 Output Compare Register - OCR0 Timer/Counter2 Output Compare Register - OCR2 Timer/Counters 0 and 2 in PWM Mode PWM Modes (Up/Down and Overflow) Asynchronous Status Register - ASSR Asynchronous Operation of Timer/Counter2 Timer/Counter1 Timer/Counter1 Control Register A - TCCR1A Timer/Counter1 Control Register B - TCCR1B Timer/Counter1 Register - TCNT1H AND TCNT1L Timer/Counter1 Output Compare Register - OCR1AH AND OCR1AL Timer/Counter1 Output Compare Register - OCR1BH AND OCR1BL Timer/Counter1 Input Capture Register - ICR1H AND ICR1L Timer/Counter1 in PWM Mode Watchdog Timer Watchdog Timer Control Register - WDTCR EEPROM Read/Write Access EEPROM Address Register - EEARH and EEARL EEPROM Data Register - EEDR EEPROM Control Register - EECR Prevent EEPROM Corruption Serial Peripheral Interface - SPI SS Pin Functionality Data Modes SPI Control Register - SPCR SPI Status Register - SPSR SPI Data Register - SPDR UARTs Data Transmission Data Reception Multi-processor Communication Mode UART Control UART0 I/O Data Register - UDR0 UART1 I/O Data Register - UDR1 UART0 Control and Status Registers - UCSR0A UART1 Control and Status Registers - UCSR1A UART0 Control and Status Registers - UCSR0B UART1 Control and Status Registers - UCSR1B Baud Rate Generator UART0 and UART1 High Byte Baud Rate Register UBRRHI UART0 Baud Rate Register Low Byte - UBRR0 UART1 Baud Rate Register Low Byte - UBRR1 Double-speed Transmission The Baud Rate Generator in Double UART Speed Mode Analog Comparator Analog Comparator Control and Status Register - ACSR Internal Voltage Reference Voltage Reference Enable Signals and Start- up Time Interface to External Memory MCU Control Register - MCUCR Extended MCU Control Register - EMCUCR Using the External Memory Interface I/O Ports Port A Port A Data Register - PORTA Port A Data Direction Register - DDRA Port A Input Pins Address - PINA Port A as General Digital I/O Port A Schematics Port B Port B Data Register - PORTB Port B Data Direction Register - DDRB Port B Input Pins Address - PINB Port B as General Digital I/O Alternate Functions of Port B Port B Schematics Port C Port C Data Register - PORTC Port C Data Direction Register - DDRC Port C Input Pins Address - PINC Port C as General Digital I/O Port C Schematics Port D Port D Data Register - PORTD Port D Data Direction Register - DDRD Port D Input Pins Address - PIND Port D as General Digital I/O Alternate Functions of Port D Port D Schematics Port E Port E Data Register - PORTE Port E Data Direction Register - DDRE Port E Input Pins Address - PINE Port E as General Digital I/O Alternate Functions of Port E Port E Schematics Memory Programming Boot Loader Support Entering the Boot Loader Program Capabilities of the Boot Loader Self-programming the Flash Setting the Boot Loader Lock bits by SPM Performing Page Erase by SPM Fill the Temporary Buffer Perform a Page Write Addressing the FLASH during Self-programming Store Program Memory Control Register - SPMCR EEPROM Write Prevents Writing to SPMCR Reading the Fuse and Lock bits from Software Program Memory Lock bits Fuse bits Signature Bytes Programming the Flash and EEPROM Parallel Programming Signal Names Enter Programming Mode Chip Erase Programming the Flash Programming the EEPROM Reading the Flash Reading the EEPROM Programming the Fuse Bits Programming the Lock Bits Reading the Fuse and Lock Bits Reading the Signature Bytes Parallel Programming Characteristics Serial Downloading Serial Programming Algorithm Data Polling Flash Data Polling EEPROM Serial Programming Characteristics Electrical Characteristics Absolute Maximum Ratings* DC Characteristics External Clock Drive Waveforms External Data Memory Timing Typical Characteristics Register Summary Instruction Set Summary (Continued) Ordering Information Packaging Information 44A 40P6 Errata ATmega161 Rev. E Data Sheet Change Log for ATmega161 Changes from Rev. 1228C-08 /02 to Rev. 1228D-02/07 Changes from Rev. 1228B-09/01 to Rev. 1228C-08/02 Table of Contents