ATmega6450 64-Kbyte self-programming Flash Program Memory, 4-Kbyte SRAM, 2-KByte EEPROM, 8 Channel 10-bit A/D-converter. JTAG interface for on-chip-debug. Up to 16 MIPS throughput at 16 MHz. 1.8 - 5.5 Volt Operation.
64-pin version: ATmega645
32KB/64-pin version: ATmega325
32KB/100-pin version: ATmega3250

ATmega640 64-Kbyte self-programming Flash Program Memory, 8-Kbyte SRAM, 4-KByte EEPROM, 16 Channel 10-bit A/D-converter. JTAG interface for on-chip-debug. Up to 16 MIPS throughput at 16 MHz. 1.8 - 5.5 Volt Operation.
128KB/64-pin version: ATmega1281
128KB/100-pin version: ATmega1280
256KB/64-pin version: ATmega2561
256KB/100-pin version: Atmega2560

ATmega128 128-Kbyte self-programming Flash Program Memory, 4-Kbyte SRAM, 4-Kbyte EEPROM, 8 Channel 10-bit A/D-converter. JTAG interface for on-chip-debug. Up to 16 MIPS throughput at 16 MHz. 2.7 - 5.5 Volt operation.

ATmega1281 128-Kbyte self-programming Flash Program Memory, 8-Kbyte SRAM, 4-KByte EEPROM, 8 Channel 10-bit A/D-converter. JTAG interface for on-chip-debug. Up to 16 MIPS throughput at 16 MHz. 1.8 - 5.5 Volt Operation.
64KB/100-pin version: ATmega640
128KB/100-pin version: ATmega1280
256KB/64-pin version: ATmega2561
256KB/100-pin version: Atmega2560

ATmega1280 128-Kbyte self-programming Flash Program Memory, 8-Kbyte SRAM, 4-KByte EEPROM, 16 Channel 10-bit A/D-converter. JTAG interface for on-chip-debug. Up to 16 MIPS throughput at 16 MHz. 1.8 - 5.5 Volt Operation.
64KB/100-pin version: ATmega640
128KB/64-pin version: ATmega1281
256KB/64-pin version: ATmega2561
256KB/100-pin version: Atmega2560

ATmega2561 256-Kbyte self-programming Flash Program Memory, 8-Kbyte SRAM, 4-KByte EEPROM, 8 Channel 10-bit A/D-converter. JTAG interface for on-chip-debug. Up to 16 MIPS throughput at 16 MHz. 1.8 - 5.5 Volt Operation.
64KB/100-pin version: ATmega640
128KB/64-pin version: ATmega1281
128KB/100-pin version: ATmega1280
256KB/100-pin version: Atmega2560

ATmega2560 256-Kbyte self-programming Flash Program Memory, 8-Kbyte SRAM, 4-KByte EEPROM, 16 Channel 10-bit A/D-converter. JTAG interface for on-chip-debug. Up to 16 MIPS throughput at 16 MHz. 1.8 - 5.5 Volt Operation.
64KB/100-pin version: ATmega640
128KB/64-pin version: ATmega1281
128KB/100-pin version: ATmega1280
256KB/64-pin version: ATmega2561

AVR microcontrollers are 8-bit on chip systems. AVR Tiny are very impressive microcontrollers. They small from outside, but inside they are not so small. In side is the same AVR RISC architecture which is compatible to all AVR microcontrollers. They have In system Programming (ISP) Flash memory, internal EEPROM and RAM, timers, interrupt sources, analog comparator, ADC and more.

Development tools for Tiny microcontrollers are the same as for other AVR MCU.

The biggest advantage of tiny microcontrollers is that they are extremely economical.

Arithmetic-Logic Unit (ALU) performs al calculations and it is connected to 32 general purpose registers directly. Because of this ALU performs one operation in one clock cycle.

Microcontroller is Harvard architecture -this means that MCU can work with data program memory and with data memory at the same time. Comparing AVR to other RISC microcontrollers it uses 2-level conveyor allowing during execution of one command to read another command code. This is why only one clock cycle is needed for execution of one command.

ATtiny family contains few series of microcontrollers:

ATtiny11 1-Kbyte In-System programmable Flash Program Memory, 32 byte SRAM, Up to 6 MIPS throughput at 6 Mhz.

ATtiny12 1-Kbyte In-System programmable Flash Program Memory, 32 byte SRAM, 64 Byte EEPROM, Up to 8 MIPS throughput at 8 Mhz.

ATtiny13 1-Kbyte In-System programmable Flash Program Memory, 64-Byte SRAM, 64-Byte EEPROM, 32-Byte Register File, 4-channel 10-bit A/D, Up to 20 MIPS throughput at 20 Mhz.

ATtiny15L 1-Kbyte In-System programmable Flash Program Memory, 64-Byte EEPROM, 32-Byte Register File, 4-channel 10-bit A/D, Up to 1.6 MIPS throughput at 1.6 MHz.

ATtiny2313 2K Bytes of In-System Self-Programmable Flash, 128 Bytes In-System Programmable EEPROM, 128 Bytes Internal SRAM. USI--Universal Serial Interface, Full Duplex UART. debugWIRE for on-chip-debug. Up to 20 MIPS throughput at 20 MHz. Compatible with Obsolete AT90S2313.

ATtiny24 2K Bytes of In-System Self-Programmable Flash, 128 Bytes In-System Programmable EEPROM, 128 Bytes Internal SRAM. 8-bit and 16-bit timer/counters with PWM, 10-bit ADC, USI-Universal Serial Interface, On-chip Temperature Sensor. debugWIRE for on-chip-debug. Up to 20 MIPS throughput at 20 MHz. 1.8 - 5.5 V operation.
8KB version: ATtiny84
4KB version: ATtiny44