An apparatus and a method for clock mode determination utilizing SCLK auto-detection and generation circuitry at a serial port which has a reduced number of pin-count by eliminating the need for inputting a master input clock signal MCLK and/or a serial input clock signal SCLK. The SCLK auto-detection and generation circuitry includes a SCLK detector circuit, a serial mode detector circuit, an internal SCLK generator circuit, a multiplexer, and an edge detector circuit. The SCLK detector circuit is used to detect whether an external serial clock signal is present and to generate a selection signal. The serial mode detector is used to detect whether an incoming data signal is in a non-TDM mode or a TDM mode and to generate a mode signal.