This is the Atmel ATmega32U4 chip used in Arduino Leonardo boards

Note: This chip DOES NOT have the Arduino Bootloader installed.

The ATmega32U4 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 ATmega32U4 achieves throughputs approaching 1 MIPS per MHz allowing the system designer to optimize power consumption versus processing speed.

The ATmega32U4 provides the following features:

• 32K bytes of In-System Programmable Flash with Read-While-Write capabilities
• 1K bytes EEPROM
• 2.5K bytes SRAM
• 26 general purpose I/O lines (CMOS outputs and LVTTL inputs)
• 32 general purpose working registers
• four flexible Timer/Counters with compare modes and PWM
• one more high-speed Timer/Counter with compare modes and PLL adjustable source
• one USART (including CTS/RTS flow control signals)
• a byte oriented 2-wire Serial Interface
• a 12-channel 10-bit ADC with optional differential input stage with programmable gain
• an on-chip calibrated temperature sensor
• a programmable Watchdog Timer with Internal Oscillator
• an SPI serial port
• IEEE std. 1149.1 comp liant 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.
• The ADC Noise Reduction mode stops the CPU and all I/O modules except 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.

DATASHEET