Disclosed is a Serializer/Deserializer physical layer circuit (SerDes PHY) for receiving and transmitting data in a half-duplex manner, the SerDes PHY including: a clock multiplication unit including a phase frequency detector (PFD), a charge pump (CP), a low pass filter, a voltage-controlled oscillator (VCO) and a loop divider; a sampling circuit sampling a received signal according to clocks from the VCO in a receive mode; a phase detector (PD) operating according to outputs of the sampling circuit; a multiplexer connecting the PD with the CP and disconnecting the PFD from the CP in the receive mode, and connecting the PFD with the CP and disconnecting the PD from the CP in a transmission mode; a parallel-to-serial converter converting parallel data into serial data according a clock from the VCO in the transmission mode; and a transmission driver outputting a transmission signal according to the serial data in the transmission mode.