Methods of operating semiconductor memory devices and semiconductor memory devices

A method of operating a semiconductor memory device including a plurality of pins configured to transfer data and signals from/to an outside of the semiconductor memory device, a memory cell array and a control logic circuit configured to control access to the memory cell array, the control logic circuit including a mode register set configured to set an operation mode of the semiconductor memory device, the method comprising:

• receiving a write command and data from the outside of the semiconductor memory device, the write command being synchronized with a main clock signal and the data being synchronized with a data clock signal;
• storing the data in the memory cell array based on a frequency-divided data clock signal which is divided from the data clock signal;
• reading data from the memory cell array in response to a read command and a target address received from the outside of the semiconductor memory device;
• and
• transmitting the read data to the outside of the semiconductor memory device selectively with a strobe signal generated based on a frequency of the main clock signal.