A multi-level signal uses the third/fourth signal level to signal both a word clock edge and a data word boundary. At the receiver, a level detector detects a transition to or from the third/fourth level as a clock signal transition and the word boundary. The bit clock can be recovered using a conventional clock multiplier. Bi-level signaling is used for data between the word boundaries. Additional signal states are available in the multi-level signal by modulating the pulse width at the third/fourth signal level.