Overview
The ATmega8U2/16U2/32U2 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 ATmega8U2/16U2/32U2 achieves throughputs approaching 1 MIPS per MHz allowing the system designer to optimize power consumption versus processing speed.

FEATUREs
• High Performance, Low Power AVR® 8-Bit Microcontroller
• Advanced RISC Architecture
   – 125 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
• Non-volatile Program and Data Memories
   – 8K/16K/32K Bytes of In-System Self-Programmable Flash
   – 512/512/1024 EEPROM
   – 512/512/1024 Internal SRAM
   – Write/Erase Cycles: 10,000 Flash/ 100,000 EEPROM
   – Data retention: 20 years at 85C/ 100 years at 25OC(1)
   – Optional Boot Code Section with Independent Lock Bits
      In-System Programming by on-chip Boot Program hardware-activated after reset
      True Read-While-Write Operation
   – Programming Lock for Software Security
• USB 2.0 Full-speed Device Module with Interrupt on Transfer Completion
   – Complies fully with Universal Serial Bus Specification REV 2.0
   – 48 MHz PLL for Full-speed Bus Operation : data transfer rates at 12 Mbit/s
   – Fully independant 176 bytes USB DPRAM for endpoint memory allocation
   – Endpoint 0 for Control Transfers: from 8 up to 64-bytes
   – 4 Programmable Endpoints:
      IN or Out Directions
      Bulk, Interrupt and IsochronousTransfers
      Programmable maximum packet size from 8 to 64 bytes
      Programmable single or double buffer
   – Suspend/Resume Interrupts
   – Microcontroller reset on USB Bus Reset without detach
   – USB Bus Disconnection on Microcontroller Request
• Peripheral Features
   – One 8-bit Timer/Counters with Separate Prescaler and Compare Mode (two 8-bit PWM channels)
   – One 16-bit Timer/Counter with Separate Prescaler, Compare and Capture Mode (three 8-bit PWM channels)
   – USART with SPI master only mode and hardware flow control (RTS/CTS)
   – Master/Slave SPI Serial Interface
   – Programmable Watchdog Timer with Separate On-chip Oscillator
   – On-chip Analog Comparator
   – Interrupt and Wake-up on Pin Change
• On Chip Debug Interface (debugWIRE)
• Special Microcontroller Features
   – Power-On Reset and Programmable Brown-out Detection
   – Internal Calibrated Oscillator
   – External and Internal Interrupt Sources
   – Five Sleep Modes: Idle, Power-save, Power-down, Standby, and Extended Standby
• I/O and Packages
   – 22 Programmable I/O Lines
   – QFN32 (5x5mm) / TQFP32 packages
• Operating Voltages
   – 2.7 - 5.5V
• Operating temperature
– Industrial (-40°C to +85°C)
• Maximum Frequency
   – 8 MHz at 2.7V - Industrial range
   – 16 MHz at 4.5V - Industrial range
   Note: 1. See “Data Retention” on page 6for details.