The Mega2560 is based on the ATmega2560 chip and has 54 digital input / output pins (15 of which can be used for PWM), 16 analog input pins, 4 UARTs (hardware serial ports), a 16 MHz crystal oscillator, a USB connection , a power jack, an ICSP header, and a reset button. The board contains everything needed to support the ATmega328 microcontroller. The Mega is compatible with most shields that are designed for the Arduino Duemilanove or Diecimila.