24.3.2.4.6 Asynchronous Data Reception

The USART includes a clock recovery and a data recovery unit for handling asynchronous data reception.

The clock recovery unit is used for synchronizing the incoming asynchronous serial frames at the RxD pin to the internally generated baud rate clock. It samples and low-pass filters each incoming bit, thereby improving the noise immunity of the receiver. The asynchronous reception operational range depends on the accuracy of the internal baud rate clock, the rate of the incoming frames, and the frame size in a number of bits.