A synchronous signal generating circuit. The synchronous signal generating circuit includes a delay locked loop (DLL), an emulator and a multiplexer. The DLL is operative to delay a reference clock signal according to a count value to generate a first output clock signal. The count value is generated according to phase difference between the first output clock signal and the reference clock signal. The emulator is operative to provide a function of the DLL and includes a programmable delay line which is operative to receive the reference clock signal and a reference count value, wherein the reference clock signal is delayed according to the reference count value to generate a second output clock signal. The multiplexer is operative to receive the first and second output clock signal and selectively output the first or second output clock signal. The first output clock signal is outputted in a first mode and the second output clock signal is outputted in a second mode.