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 con-
ventional 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, 10-bit 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-Programmable Flash on a monolithic chip,
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 sys-
tem development tools including: C compilers, macro assemblers, program
debugger/simulators, in-circuit emulators, and evaluation kits.
6
ATmega640/1280/1281/2560/2561
2549LS–AVR–08/07
ATMEL [ ATMEL CORPORATION ]
