Encoding / Decoding

The USART configured in LON mode encodes transmitted data and decodes received data using differential Manchester encoding. In differential Manchester encoding, a ‘1’ bit is indicated by making the first half of the signal equal to the last half of the previous bit's signal (no transition at the start of the bit-time). A ‘0’ bit is indicated by making the first half of the signal opposite to the last half of the previous bit's signal (a zero bit is indicated by a transition at the beginning of the bit-time). As is the case with normal Manchester encoding, missing transition at the middle of bit-time represents a Manchester code violation.

The FLEX_US_MAN.RXIDLEV bit informs the USART of the receiver line idle state value (receiver line inactive) thus ensuring higher reliability of preamble synchronization. By default, RXIDLEV is set (receiver line is at level 1 when there is no activity).

Differential Manchester encoding is polarity-insensitive.