ATMEGA1280V

Features • High Performance, Low Power AVR® 8-Bit Microcontroller • Advanced RISC Architecture – 135 Powerful Instructions – Most Single Clock Cycle Execution – 32 x 8 General Purpose Working Registers – Fully Static Operation – Up to 16 MIPS Throughput at 16 MHz – On-Chip 2-cycle Multiplier Non-volatile Program and Data Memories – 64K/128K/256K Bytes of In-System Self-Programmable Flash Endurance: 10,000 Write/Erase Cycles – Optional Boot Code Section with Independent Lock Bits In-System Programming by On-chip Boot Program True Read-While-Write Operation – 4K Bytes EEPROM Endurance: 100,000 Write/Erase Cycles – 8K Bytes Internal SRAM – Up to 64K Bytes Optional External Memory Space – Programming Lock for Software Security JTAG (IEEE std. 1149.1 compliant) Interface – Boundary-scan Capabilities According to the JTAG Standard – Extensive On-chip Debug Support – Programming of Flash, EEPROM, Fuses, and Lock Bits through the JTAG Interface Peripheral Features – Two 8-bit Timer/Counters with Separate Prescaler and Compare Mode – Four 16-bit Timer/Counter with Separate Prescaler, Compare- and Capture Mode – Real Time Counter with Separate Oscillator – Four 8-bit PWM Channels – Six/Twelve PWM Channels with Programmable Resolution from 2 to 16 Bits (ATmega1281/2561, ATmega640/1280/2560) – Output Compare Modulator – 8/16-channel, 10-bit ADC (ATmega1281/2561, ATmega640/1280/2560) – Two/Four Programmable Serial USART (ATmega1281/2561,ATmega640/1280/2560) – Master/Slave SPI Serial Interface – Byte Oriented 2-wire Serial Interface – Programmable Watchdog Timer with Separate On-chip Oscillator – On-chip Analog Comparator – Interrupt and Wake-up on Pin Change Special Microcontroller Features – Power-on Reset and Programmable Brown-out Detection – Internal Calibrated Oscillator – External and Internal Interrupt Sources – Six Sleep Modes: Idle, ADC Noise Reduction, Power-save, Power-down, Standby, and Extended Standby I/O and Packages – 54/86 Programmable I/O Lines (ATmega1281/2561, ATmega640/1280/2560) – 64-pad QFN/MLF, 64-lead TQFP (ATmega1281/2561) – 100-lead TQFP, 100-ball CBGA (ATmega640/1280/2560) – RoHS/Fully Green Temperature Range: – -40°C to 85°C Industrial Ultra-Low Power Consumption – Active Mode: 1 MHz, 1.8V: 510 µA – Power-down Mode: 0.1 µA at 1.8V Speed Grade (see “Maximum speed vs. VCC” on page 377): – ATmega640V/ATmega1280V/ATmega1281V: 0 - 4 MHz @ 1.8 - 5.5V, 0 - 8 MHz @ 2.7 - 5.5V – ATmega2560V/ATmega2561V: 0 - 2 MHz @ 1.8 - 5.5V, 0 - 8 MHz @ 2.7 - 5.5V – ATmega640/ATmega1280/ATmega1281: 0 - 8 MHz @ 2.7 - 5.5V, 0 - 16 MHz @ 4.5 - 5.5V – ATmega2560/ATmega2561: 0 - 16 MHz @ 4.5 - 5.5V • • • 8-bit Microcontroller with 64K/128K/256K Bytes In-System Programmable Flash ATmega640/V ATmega1280/V ATmega1281/V ATmega2560/V ATmega2561/V Preliminary • • • • • 2549K–AVR–01/07 Pin Configurations Figure 1. TQFP-pinout ATmega640/1280/2560 PK2 (ADC10/PCINT18) PK3 (ADC11/PCINT19) PK4 (ADC12/PCINT20) PK5 (ADC13/PCINT21) PK6 (ADC14/PCINT22) PF5 (ADC5/TMS) PF6 (ADC6/TDO) PF4 (ADC4/TCK) PF7 (ADC7/TDI) PK7 (ADC15/PCINT23) PK0 (ADC8/PCINT16) PK1 (ADC9/PCINT17) PF1 (ADC1) PF2 (ADC2) PF0 (ADC0) PF3 (ADC3) PA0 (AD0) PA1 (AD1) 100 99 (OC0B) PG5 (RXD0/PCINT8) PE0 (TXD0) PE1 (XCK0/AIN0) PE2 (OC3A/AIN1) PE3 (OC3B/INT4) PE4 (OC3C/INT5) PE5 (T3/INT6) PE6 (CLKO/ICP3/INT7) PE7 VCC GND (RXD2) PH0 (TXD2) PH1 (XCK2) PH2 (OC4A) PH3 (OC4B) PH4 (OC4C) PH5 (OC2B) PH6 (SS/PCINT0) PB0 (SCK/PCINT1) PB1 (MOSI/PCINT2) PB2 (MISO/PCINT3) PB3 (OC2A/PCINT4) PB4 (OC1A/PCINT5) PB5 (OC1B/PCINT6) PB6 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 (OC0A/OC1C/PCINT7) PB7 98 97 96 95 94 93 92 91 90 89 88 87 86 85 84 83 82 81 80 79 78 77 PA2 (AD2) AVCC AREF GND GND VCC PJ7 76 75 74 PA3 (AD3) PA4 (AD4) PA5 (AD5) PA6 (AD6) PA7 (AD7) PG2 (ALE) PJ6 (PCINT15) PJ5 (PCINT14) PJ4 (PCINT13) PJ3 (PCINT12) PJ2 (XCK3/PCINT11) PJ1 (TXD3/PCINT10) PJ0 (RXD3/PCINT9) GND VCC PC7 (A15) PC6 (A14) PC5 (A13) PC4 (A12) PC3 (A11) PC2 (A10) PC1 (A9) PC0 (A8) PG1 (RD) PG0 (WR) INDEX CORNER 73 72 71 70 69 68 67 66 65 64 ATmega640/1280/2560 63 62 61 60 59 58 57 56 55 54 53 52 51 27 (T4) PH7 28 (TOSC2) PG3 29 (TOSC1) PG4 30 RESET 31 VCC 32 GND 33 XTAL2 34 XTAL1 35 (ICP4) PL0 36 (ICP5) PL1 37 (T5) PL2 38 (OC5A) PL3 39 (OC5B) PL4 40 (OC5C) PL5 41 PL6 42 PL7 43 (SCL/INT0) PD0 44 (SDA/INT1) PD1 45 (RXD1/INT2) PD2 46 (TXD1/INT3) PD3 47 (ICP1) PD4 48 (XCK1) PD5 49 (T1) PD6 50 (T0) PD7 2 ATmega640/1280/1281/2560/2561 2549K–AVR–01/07 ATmega640/1280/1281/2560/2561 Figure 2. CBGA-pinout ATmega640/1280/2560 Top view 1 A B C D E F G H J K 2 3 4 5 6 7 8 9 10 10 9 8 Bottom view 7 6 5 4 3 2 1 A B C D E F G H J K Table 1. CBGA-pinout ATmega640/1280/2560. 1 A B C D E F G H J K GND AVCC PE2 PE3 PE7 VCC GND PB3 PH7 PB7 2 AREF PG5 PE0 PE4 PH0 PH4 PB1 PB4 PG3 PG4 3 PF0 PF1 PE1 PE5 PH1 PH6 PB2 RESET PB6 VCC 4 PF2 PF3 PF4 PE6 PH3 PB0 PB5 PL1 PL0 GND 5 PF5 PF6 PF7 PH2 PH5 PL4 PL2 PL3 XTAL2 XTAL1 6 PK0 PK1 PK2 PA4 PJ6 PD1 PD0 PL7 PL6 PL5 7 PK3 PK4 PK5 PA5 PJ5 PJ1 PD5 PD4 PD3 PD2 8 PK6 PK7 PJ7 PA6 PJ4 PJ0 PC5 PC4 PC1 PD6 9 GND PA0 PA1 PA7 PJ3 PC7 PC6 PC3 PC0 PD7 10 VCC PA2 PA3 PG2 PJ2 GND VCC PC2 PG1 PG0 3 2549K–AVR–01/07 Figure 3. Pinout ATmega1281/2561 PF6 (ADC6/TDO) PF4 (ADC4/TCK) PF5 (ADC5/TMS) PF7 (ADC7/TDI) PF0 (ADC0) PF1 (ADC1) PF2 (ADC2) PF3 (ADC3) PA0 (AD0) PA1 (AD1) 50 64 63 62 61 60 59 58 57 56 55 54 53 52 51 (OC0B) PG5 (RXD0/PCINT8/PDI) PE0 (TXD0/PDO) PE1 (XCK0/AIN0) PE2 (OC3A/AIN1) PE3 (OC3B/INT4) PE4 (OC3C/INT5) PE5 (T3/INT6) PE6 (ICP3/CLKO/INT7) PE7 (SS/PCINT0) PB0 (SCK/ PCINT1) PB1 (MOSI/ PCINT2) PB2 (MISO/ PCINT3) PB3 (OC2A/ PCINT4) PB4 (OC1A/PCINT5) PB5 (OC1B/PCINT6) PB6 1 2 3 4 5 6 7 8 INDEX CORNER 49 PA2 (AD2) AVCC GND AREF GND VCC 48 47 46 45 44 43 42 PA3 (AD3) PA4 (AD4) PA5 (AD5) PA6 (AD6) PA7 (AD7) PG2 (ALE) PC7 (A15) PC6 (A14) PC5 (A13) PC4 (A12) PC3 (A11) PC2 (A10) PC1 (A9) PC0 (A8) PG1 (RD) PG0 (WR) ATmega1281/2561 9 10 11 12 13 14 15 16 41 40 39 38 37 36 35 34 33 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 (T1) PD6 (RXD1/INT2) PD2 (SCL/INT0) PD0 (TXD1/INT3) PD3 (OC0A/OC1C/PCINT7) PB7 (XCK1) PD5 (ICP1) PD4 VCC Note: The large center pad underneath the QFN/MLF package is made of metal and internally connected to GND. It should be soldered or glued to the board to ensure good mechanical stability. If the center pad is left unconnected, the package might loosen from the board. Disclaimer Typical values contained in this datasheet are based on simulations and characterization of other AVR microcontrollers manufactured on the same process technology. Min. and Max values will be available after the device is characterized. 4 ATmega640/1280/1281/2560/2561 2549K–AVR–01/07 (SDA/INT1) PD1 (TOSC2) PG3 (TOSC1) PG4 (T0) PD7 GND XTAL2 RESET XTAL1 32 ATmega640/1280/1281/2560/2561 Overview The ATmega640/1280/1281/2560/2561 is a low-power CMOS 8-bit microcontroller based on the AVR enhanced RISC architecture. By executing powerful instructions in a single clock cycle, the ATmega640/1280/1281/2560/2561 achieves throughputs approaching 1 MIPS per MHz allowing the system designer to optimize power consumption versus processing speed. Block Diagram Figure 4. Block Diagram PF7..0 VCC PK7..0 PJ7..0 PE7..0 RESET Power Supervision POR / BOD & RESET PORT F (8) PORT K (8) PORT J (8) PORT E (8) GND Watchdog Timer Watchdog Oscillator JTAG A/D Converter Analog Comparator USART 0 XTAL1 Oscillator Circuits / Clock Generation EEPROM Internal Bandgap reference 16bit T/C 3 XTAL2 CPU 16bit T/C 5 USART 3 PA7..0 PORT A (8) 16bit T/C 4 USART 1 PG5..0 PORT G (6) XRAM FLASH SRAM 16bit T/C 1 PC7..0 PORT C (8) TWI SPI 8bit T/C 0 8bit T/C 2 USART 2 NOTE: Shaded parts only available in the 100-pin version. Complete functionality for the ADC, T/C4, and T/C5 only available in the 100-pin version. PORT D (8) PORT B (8) PORT H (8) PORT L (8) PD7..0 PB7..0 PH7..0 PL7..0 5 2549K–AVR–01/07 The AVR core combines a rich instruction set with 32 general purpose working registers. All the 32 registers are directly connected to the Arithmetic Logic Unit (ALU), allowing two independent registers to be accessed in one single instruction executed in one clock cycle. The resulting architecture is more code efficient while achieving throughputs up to ten times faster than conventional CISC microcontrollers. The ATmega640/1280/1281/2560/2561 provides the following features: 64K/128K/256K bytes of In-System Programmable Flash with Read-While-Write capabilities, 4K bytes EEPROM, 8K bytes SRAM, 54/86 general purpose I/O lines, 32 general purpose working registers, Real Time Counter (RTC), six flexible Timer/Counters with compare modes and PWM, 4 USARTs, a byte oriented 2-wire Serial Interface, a 16-channel, 10bit ADC with optional differential input stage with programmable gain, programmable Watchdog Timer with Internal Oscillator, an SPI serial port, IEEE std. 1149.1 compliant JTAG test interface, also used for accessing the On-chip Debug system and programming and six software selectable power saving modes. The Idle mode stops the CPU while allowing the SRAM, Timer/Counters, SPI port, and interrupt system to continue functioning. The Power-down mode saves the register contents but freezes the Oscillator, disabling all other chip functions until the next interrupt or Hardware Reset. In Power-save mode, the asynchronous timer continues to run, allowing the user to maintain a timer base while the rest of the device is sleeping. The ADC Noise Reduction mode stops the CPU and all I/O modules except Asynchronous Timer and ADC, to minimize switching noise during ADC conversions. In Standby mode, the Crystal/Resonator Oscillator is running while the rest of the device is sleeping. This allows very fast start-up combined with low power consumption. In Extended Standby mode, both the main Oscillator and the Asynchronous Timer continue to run. The device is manufactured using Atmel’s high-density nonvolatile memory technology. The On-chip ISP Flash allows the program memory to be reprogrammed in-system through an SPI serial interface, by a conventional nonvolatile memory programmer, or by an On-chip Boot program running on the AVR core. The boot program can use any interface to download the application program in the application Flash memory. Software in the Boot Flash section will continue to run while the Application Flash section is updated, providing true Read-While-Write operation. By combining an 8-bit RISC CPU with In-System Self-Program mable Flash on a monolithic ch ip, the Atmel ATmega640/1280/1281/2560/2561 is a powerful microcontroller that provides a highly flexible and cost effective solution to many embedded control applications. The ATmega640/1280/1281/2560/2561 AVR is supported with a full suite of program and system development tools including: C compilers, macro assemblers, program debugger/simulators, in-circuit emulators, and evaluation kits. 6 ATmega640/1280/1281/2560/2561 2549K–AVR–01/07 ATmega640/1280/1281/2560/2561 Comparison Between ATmega1281/2561 and ATmega640/1280/2560 Each device in the ATmega640/1280/1281/2560/2561 family differs only in memory size and number of pins. Table 2 summarizes the different configurations for the six devices. Table 2. Configuration Summary Device ATmega640 ATmega1280 ATmega1281 ATmega2560 ATmega2561 Flash 64KB 128KB 128KB 256KB 256KB EEPROM 4KB 4KB 4KB 4KB 4KB RAM 8KB 8KB 8KB 8KB 8KB General Purpose I/O pins 86 86 54 86 54 16 bits resolution PWM channels 12 12 6 12 6 Serial USARTs 4 4 2 4 2 ADC Channels 16 16 8 16 8 Pin Descriptions VCC GND Port A (PA7..PA0) Digital supply voltage. Ground. Port A is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port A output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port A pins that are externally pulled low will source current if the pull-up resistors are activated. The Port A pins are tri-stated when a reset condition becomes active, even if the clock is not running. Port A also serves the functions of various special features of the ATmega640/1280/1281/2560/2561 as listed on page 91. Port B (PB7..PB0) Port B is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port B output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port B pins that are externally pulled low will source current if the pull-up resistors are activated. The Port B pins are tri-stated when a reset condition becomes active, even if the clock is not running. Port B has better driving capabilities than the other ports. Port B also serves the functions of various special features of the ATmega640/1280/1281/2560/2561 as listed on page 92. Port C (PC7..PC0) Port C is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port C output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port C pins that are externally pulled low will source current if the pull-up resistors are activated. The Port C pins are tri-stated when a reset condition becomes active, even if the clock is not running. Port C also serves the functions of special ATmega640/1280/1281/2560/2561 as listed on page 95. Port D (PD7..PD0) features of the Port D is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port D output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port D pins that are externally pulled low will source 7 2549K–AVR–01/07 current if the pull-up resistors are activated. The Port D pins are tri-stated when a reset condition becomes active, even if the clock is not running. Port D also serves the functions of various special features of the ATmega640/1280/1281/2560/2561 as listed on page 97. Port E (PE7..PE0) Port E is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port E output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port E pins that are externally pulled low will source current if the pull-up resistors are activated. The Port E pins are tri-stated when a reset condition becomes active, even if the clock is not running. Port E also serves the functions of various special features of the ATmega640/1280/1281/2560/2561 as listed on page 99. Port F (PF7..PF0) Port F serves as analog inputs to the A/D Converter. Port F also serves as an 8-bit bi-directional I/O port, if the A/D Converter is not used. Port pins can provide internal pull-up resistors (selected for each bit). The Port F output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port F pins that are externally pulled low will source current if the pull-up resistors are activated. The Port F pins are tri-stated when a reset condition becomes active, even if the clock is not running. If the JTAG interface is enabled, the pull-up resistors on pins PF7(TDI), PF5(TMS), and PF4(TCK) will be activated even if a reset occurs. Port F also serves the functions of the JTAG interface. Port G (PG5..PG0) Port G is a 6-bit I/O port with internal pull-up resistors (selected for each bit). The Port G output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port G pins that are externally pulled low will source current if the pull-up resistors are activated. The Port G pins are tri-stated when a reset condition becomes active, even if the clock is not running. Port G also serves the functions of various special features of the ATmega640/1280/1281/2560/2561 as listed on page 105. Port H (PH7..PH0) Port H is a 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port H output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port H pins that are externally pulled low will source current if the pull-up resistors are activated. The Port H pins are tri-stated when a reset condition becomes active, even if the clock is not running. Port H also serves the functions of various special features of the ATmega640/1280/2560 as listed on page 107. Port J (PJ7..PJ0) Port J is a 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port J output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port J pins that are externally pulled low will source current if the pull-up resistors are activated. The Port J pins are tri-stated when a reset condition becomes active, even if the clock is not running. Port J also serves the functions of various special features of the ATmega640/1280/2560 as listed on page 109. Port K (PK7..PK0) Port K serves as analog inputs to the A/D Converter. 8 ATmega640/1280/1281/2560/2561 2549K–AVR–01/07 ATmega640/1280/1281/2560/2561 Port K is a 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port K output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port K pins that are externally pulled low will source current if the pull-up resistors are activated. The Port K pins are tri-stated when a reset condition becomes active, even if the clock is not running. Port K also serves the functions of various special features of the ATmega640/1280/2560 as listed on page 111. Port L (PL7..PL0) Port L is a 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port L output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port L pins that are externally pulled low will source current if the pull-up resistors are activated. The Port L pins are tri-stated when a reset condition becomes active, even if the clock is not running. Port L also serves the functions of various special features of the ATmega640/1280/2560 as listed on page 113. RESET Reset input. A low level on this pin for longer than the minimum pulse length will generate a reset, even if the clock is not running. The minimum pulse length is given in Table 26 on page 58. Shorter pulses are not guaranteed to generate a reset. Input to the inverting Oscillator amplifier and input to the internal clock operating circuit. Output from the inverting Oscillator amplifier. AVCC is the supply voltage pin for Port F and the A/D Converter. It should be externally connected to VCC, even if the ADC is not used. If the ADC is used, it should be connected to VCC through a low-pass filter. This is the analog reference pin for the A/D Converter. XTAL1 XTAL2 AVCC AREF Resources A comprehensive set of development tools and application notes, and datasheets are available for download on http://www.atmel.com/avr. About Code Examples This documentation contains simple code examples that briefly show how to use various parts of the device. Be aware that not all C compiler vendors include bit definitions in the header files and interrupt handling in C is compiler dependent. Please confirm with the C compiler documentation for more details. These code examples assume that the part specific header file is included before compilation. For I/O registers located in extended I/O map, "IN", "OUT", "SBIS", "SBIC", "CBI", and "SBI" instructions must be replaced with instructions that allow access to extended I/O. Typically "LDS" and "STS" combined with "SBRS", "SBRC", "SBR", and "CBR". 9 2549K–AVR–01/07 AVR CPU Core Introduction This section discusses the AVR core architecture in general. The main function of the CPU core is to ensure correct program execution. The CPU must therefore be able to access memories, perform calculations, control peripherals, and handle interrupts. Figure 5. Block Diagram of the AVR Architecture Architectural Overview Data Bus 8-bit Flash Program Memory Program Counter Status and Control Instruction Register 32 x 8 General Purpose Registrers Interrupt Unit SPI Unit Watchdog Timer Indirect Addressing Instruction Decoder Direct Addressing ALU Control Lines Analog Comparator I/O Module1 Data SRAM I/O Module 2 I/O Module n EEPROM I/O Lines In order to maximize performance and parallelism, the AVR uses a Harvard architecture – with separate memories and buses for program and data. Instructions in the program memory are executed with a single level pipelining. 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 InSystem Reprogrammable Flash memory. The fast-access Register File contains 32 x 8-bit general purpose working registers with a single clock cycle access time. This allows single-cycle Arithmetic Logic Unit (ALU) operation. In a typical ALU operation, two operands are output from the Register File, 10 ATmega640/1280/1281/2560/2561 2549K–AVR–01/07 ATmega640/1280/1281/2560/2561 the operation is executed, and the result is stored back in the Register File – in one clock cycle. Six of the 32 registers can be used as three 16-bit indirect address register pointers for Data Space addressing – enabling efficient address calculations. One of the these address pointers can also be used as an address pointer for look up tables in Flash program memory. These added function registers are the 16-bit X-, Y-, and Z-register, described later in this section. The ALU supports arithmetic and logic operations between registers or between a constant and a register. Single register operations can also be executed in the ALU. After an arithmetic operation, the Status Register is updated to reflect information about the result of the operation. Program flow is provided by conditional and unconditional jump and call instructions, able to directly address the whole address space. Most AVR instructions have a single 16-bit word format. Every program memory address contains a 16- or 32-bit instruction. Program Flash memory space is divided in two sections, the Boot Program section and the Application Program section. Both sections have dedicated Lock bits for write and read/write protection. The SPM instruction that writes into the Application Flash memory section must reside in the Boot Program section. 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 in the Reset routine (before subroutines or interrupts are executed). The Stack Pointer (SP) is read/write accessible in the I/O space. The data SRAM can easily be 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. A flexible interrupt module has its control registers in the I/O space with an additional Global Interrupt Enable bit in the Status Register. All interrupts have a separate Interrupt Vector in the Interrupt Vector table. The interrupts have priority in accordance with their Interrupt Vector position. The lower the Interrupt Vector address, the higher the priority. The I/O memory space contains 64 addresses for CPU peripheral functions as Control Registers, SPI, 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, 0x20 - 0x5F. In addition, the ATmega640/1280/1281/2560/2561 has Extended I/O space from 0x60 - 0x1FF in SRAM where only the ST/STS/STD and LD/LDS/LDD instructions can be used. ALU – Arithmetic Logic Unit The high-performance AVR ALU operates in direct connection with all the 32 general purpose working registers. Within a single clock cycle, arithmetic operations between general purpose registers or between a register and an immediate are executed. The ALU operations are divided into three main categories – arithmetic, logical, and bit-functions. Some implementations of the architecture also provide a powerful multiplier supporting both signed/unsigned multiplication and fractional format. See the “Instruction Set” section for a detailed description. The Status Register contains information about the result of the most recently executed arithmetic instruction. This information can be used for altering program flow in order to perform conditional operations. Note that the Status Register is updated after all ALU operations, as specified in the Instruction Set Reference. This will in many cases Status Register 11 2549K–AVR–01/07 remove the need for using the dedicated compare instructions, resulting in faster and more compact code. The Status Register is not automatically stored when entering an interrupt routine and restored when returning from an interrupt. This must be handled by software. SREG – AVR Status Register The AVR Status Register – SREG – is defined as: Bit 0x3F (0x5F) Read/Write Initial Value 7 I R/W 0 6 T R/W 0 5 H R/W 0 4 S R/W 0 3 V R/W 0 2 N R/W 0 1 Z R/W 0 0 C R/W 0 SREG • Bit 7 – I: Global Interrupt Enable The Global Interrupt Enable bit must be set for the interrupts to be enabled. The individual interrupt enable control is then performed in separate control registers. If the Global Interrupt Enable Register is cleared, none of the interrupts are enabled independent of the individual interrupt enable settings. The I-bit is cleared by hardware after an interrupt has occurred, and is set by the RETI instruction to enable subsequent interrupts. The Ibit can also be set and cleared by the application with the SEI and CLI instructions, as described in the instruction set reference. • Bit 6 – T: Bit Copy Storage The Bit Copy instructions BLD (Bit LoaD) and BST (Bit STore) use the T-bit as source or destination for the operated bit. A bit from a register in the Register File can be copied into T by the BST instruction, and a bit in T can be copied into a bit in a register in the Register File by the BLD instruction. • Bit 5 – H: Half Carry Flag The Half Carry Flag H indicates a Half Carry in some arithmetic operations. Half Carry Is useful in BCD arithmetic. See the “Instruction Set Description” for detailed information. • Bit 4 – S: Sign Bit, S = N ⊕V The S-bit is always an exclusive or between the Negative Flag N and the Two’s Complement Overflow Flag V. See the “Instruction Set Description” for detailed information. • Bit 3 – V: Two’s Complement Overflow Flag The Two’s Complement Overflow Flag V supports two’s complement arithmetics. See the “Instruction Set Description” for detailed information. • Bit 2 – N: Negative Flag The Negative Flag N indicates a negative result in an arithmetic or logic operation. See the “Instruction Set Description” for detailed information. • Bit 1 – Z: Zero Flag The Zero Flag Z indicates a zero result in an arithmetic or logic operation. See the “Instruction Set Description” for detailed information. • Bit 0 – C: Carry Flag The Carry Flag C indicates a carry in an arithmetic or logic operation. See the “Instruction Set Description” for detailed information. 12 ATmega640/1280/1281/2560/2561 2549K–AVR–01/07 ATmega640/1280/1281/2560/2561 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 6 shows the structure of the 32 general purpose working registers in the CPU. Figure 6. AVR CPU General Purpose Working Registers 7 R0 R1 R2 … R13 General Purpose Working Registers R14 R15 R16 R17 … R26 R27 R28 R29 R30 R31 0x1A 0x1B 0x1C 0x1D 0x1E 0x1F X-register Low Byte X-register High Byte Y-register Low Byte Y-register High Byte Z-register Low Byte Z-register High Byte 0x0D 0x0E 0x0F 0x10 0x11 0 Addr. 0x00 0x01 0x02 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 6 on page 13, 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 implemented 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. 13 2549K–AVR–01/07 The X-register, Y-register, and Z-register The registers R26..R31 have some added functions to their general purpose usage. These registers 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 7. Figure 7. The X-, Y-, and Z-registers 15 X-register 7 R27 (0x1B) XH 0 7 R26 (0x1A) XL 0 0 15 Y-register 7 R29 (0x1D) 15 Z-register 7 R31 (0x1F) YH 0 7 R28 (0x1C) ZH 0 7 R30 (0x1E) YL 0 0 ZL 0 0 In the different addressing modes these address registers have functions as fixed displacement, automatic increment, and automatic decrement (see the instruction set reference for details). Stack Pointer The Stack is mainly used for storing temporary data, for storing local variables and for storing return addresses after interrupts and subroutine calls. The Stack Pointer Register always points to the top of the Stack. Note that the Stack is implemented as growing from higher memory locations to lower memory locations. This implies that a Stack PUSH command decreases the Stack Pointer. The Stack Pointer points to the data SRAM Stack area where the Subroutine and Interrupt Stacks are located. This Stack space in the data SRAM must be defined by the program before any subroutine calls are executed or interrupts are enabled. The Stack Pointer must be set to point above 0x0200. The initial value of the stack pointer is the last address of the internal SRAM. The Stack Pointer is decremented by one when data is pushed onto the Stack with the PUSH instruction, and it is decremented by two for ATmega640/1280/1281 and three for ATmega2560/2561 when the return address is pushed onto the Stack with subroutine call or interrupt. The Stack Pointer is incremented by one when data is popped from the Stack with the POP instruction, and it is incremented by two for ATmega640/1280/1281 and three for ATmega2560/2561 when data is popped from the Stack with return from subroutine RET or return from interrupt RETI. The AVR Stack Pointer is implemented as two 8-bit registers in the I/O space. The number of bits actually used is implementation dependent. Note that the data space in some implementations of the AVR architecture is so small that only SPL is needed. In this case, the SPH Register will not be present. Bit 0x3E (0x5E) 0x3D (0x5D) 15 SP15 SP7 7 Read/Write R/W R/W Initial Value 0 1 14 SP14 SP6 6 R/W R/W 0 1 13 SP13 SP5 5 R/W R/W 1 1 12 SP12 SP4 4 R/W R/W 0 1 11 SP11 SP3 3 R/W R/W 0 1 10 SP10 SP2 2 R/W R/W 0 1 9 SP9 SP1 1 R/W R/W 0 1 8 SP8 SP0 0 R/W R/W 1 1 SPH SPL 14 ATmega640/1280/1281/2560/2561 2549K–AVR–01/07 ATmega640/1280/1281/2560/2561 RAMPZ – Extended Z-pointer Register for ELPM/SPM Bit 0x3B (0x5B) Read/Write Initial Value 7 RAMPZ7 6 RAMPZ6 5 RAMPZ5 4 RAMPZ4 3 RAMPZ3 2 RAMPZ2 1 RAMPZ1 0 RAMPZ0 RAMPZ R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 For ELPM/SPM instructions, the Z-pointer is a concatenation of RAMPZ, ZH, and ZL, as shown in Figure 8. Note that LPM is not affected by the RAMPZ setting. Figure 8. The Z-pointer used by ELPM and SPM Bit ( Individually) 7 RAMPZ 0 7 ZH 0 7 ZL 0 Bit (Z-pointer) 23 16 15 8 7 0 The actual number of bits is implementation dependent. Unused bits in an implementation will always read as zero. For compatibility with future devices, be sure to write these bits to zero. EIND – Extended Indirect Register Bit 0x3C (0x5C) Read/Write Initial Value 7 EIND7 R/W 0 6 EIND6 R/W 0 5 EIND5 R/W 0 4 EIND4 R/W 0 3 EIND3 R/W 0 2 EIND2 R/W 0 1 EIND1 R/W 0 0 EIND0 R/W 0 EIND For EICALL/EIJMP instructions, the Indirect-pointer to the subroutine/routine is a concatenation of EIND, ZH, and ZL, as shown in Figure 9. Note that ICALL and IJMP are not affected by the EIND setting. Figure 9. The Indirect-pointer used by EICALL and EIJMP Bit (Individually) 7 EIND 0 7 ZH 0 7 ZL 0 Bit (Indirectpointer) 23 16 15 8 7 0 The actual number of bits is implementation dependent. Unused bits in an implementation will always read as zero. For compatibility with future devices, be sure to write these bits to zero. 15 2549K–AVR–01/07 Instruction Execution Timing This section describes the general access timing concepts for instruction execution. The AVR CPU is driven by the CPU clock clkCPU, directly generated from the selected clock source for the chip. No internal clock division is used. Figure 10 shows the parallel instruction fetches and instruction executions enabled by the Harvard architecture and the fast-access Register File concept. This is the basic pipelining concept to obtain up to 1 MIPS per MHz with the corresponding unique results for functions per cost, functions per clocks, and functions per power-unit. Figure 10. The Parallel Instruction Fetches and Instruction Executions T1 T2 T3 T4 clkCPU 1st Instruction Fetch 1st Instruction Execute 2nd Instruction Fetch 2nd Instruction Execute 3rd Instruction Fetch 3rd Instruction Execute 4th Instruction Fetch Figure 11 shows the internal timing concept for the Register File. In a single clock cycle an ALU operation using two register operands is executed, and the result is stored back to the destination register. Figure 11. Single Cycle ALU Operation T1 T2 T3 T4 clkCPU Total Execution Time Register Operands Fetch ALU Operation Execute Result Write Back 16 ATmega640/1280/1281/2560/2561 2549K–AVR–01/07 ATmega640/1280/1281/2560/2561 Reset and Interrupt Handling The AVR provides several different interrupt sources. These interrupts and the separate Reset Vector each have a separate program vector in the program memory space. All interrupts are assigned individual enable bits which must be written logic one together with the Global Interrupt Enable bit in the Status Register in order to enable the interrupt. Depending on the Program Counter value, interrupts may be automatically disabled when Boot Lock bits BLB02 or BLB12 are programmed. This feature improves software security. See the section “Memory Programming” on page 342 for details. The lowest addresses in the program memory space are by default defined as the Reset and Interrupt Vectors. The complete list of vectors is shown in “Interrupts” on page 69. The list also determines the priority levels of the different interrupts. The lower the address the higher is the priority level. RESET has the highest priority, and next is INT0 – the External Interrupt Request 0. The Interrupt Vectors can be moved to the start of the Boot Flash section by setting the IVSEL bit in the MCU Control Register (MCUCR). Refer to “Interrupts” on page 69 for more information. The Reset Vector can also be moved to the start of the Boot Flash section by programming the BOOTRST Fuse, see “Memory Programming” on page 342. When an interrupt occurs, the Global Interrupt Enable I-bit is cleared and all interrupts are disabled. The user software can write logic one to the I-bit to enable nested interrupts. All enabled interrupts can then interrupt the current interrupt routine. The I-bit is automatically set when a Return from Interrupt instruction – RETI – is executed. There are basically two types of interrupts. The first type is triggered by an event that sets the Interrupt Flag. For these interrupts, the Program Counter is vectored to the actual Interrupt Vector in order to execute the interrupt handling routine, and hardware clears the corresponding Interrupt Flag. Interrupt Flags can also be cleared by writing a logic one to the flag bit position(s) to be cleared. If an interrupt condition occurs while the corresponding interrupt enable bit is cleared, the Interrupt Flag will be set and remembered until the interrupt is enabled, or the flag is cleared by software. Similarly, if one or more interrupt conditions occur while the Global Interrupt Enable bit is cleared, the corresponding Interrupt Flag(s) will be set and remembered until the Global Interrupt Enable bit is set, and will then be executed by order of priority. The second type of interrupts will trigger as long as the interrupt condition is present. These interrupts do not necessarily have Interrupt Flags. If the interrupt condition disappears before the interrupt is enabled, the interrupt will not be triggered. When the AVR exits from an interrupt, it will always return to the main program and execute one more instruction before any pending interrupt is served. Note that the Status Register is not automatically stored when entering an interrupt routine, nor restored when returning from an interrupt routine. This must be handled by software. When using the CLI instruction to disable interrupts, the interrupts will be immediately disabled. No interrupt will be executed after the CLI instruction, even if it occurs simulta- 17 2549K–AVR–01/07 neously with the CLI instruction. The following example shows how this can be used to avoid interrupts during the timed EEPROM write sequence. Assembly Code Example in cli r16, SREG ; store SREG value ; start EEPROM write ; restore SREG value (I-bit) ; disable interrupts during timed sequence sbi EECR, EEMPE sbi EECR, EEPE out SREG, r16 C Code Example char cSREG; cSREG = SREG; /* store SREG value */ /* disable interrupts during timed sequence */ __disable_interrupt(); EECR |= (1