Peripherals and I/O — what is on board
Ten I/O lines are available, along with a Brown-out Detect/Reset, POR, a PWM timer, and a watchdog timer. The Universal Serial Interface (USI) supports I²C and SPI in hardware — no bit-banging needed for common sensor or memory interfaces. There is no on-chip ADC, so analog inputs require an external converter. An internal oscillator is included, saving a crystal in cost-sensitive designs.
The 16-QFN with exposed pad helps pull heat into the PCB ground plane, though at the 16 MHz core speed and typical active current, dissipation is low enough that thermal management is straightforward.