Semiconductor memory device

A semiconductor memory device includes a memory cell array, an address register for taking in an address synchronizing with a clock, a decode circuit for selecting a memory cell of the memory cell array by decoding the address retained in the address register, a reading/writing circuit for reading data from the memory cell array and writing the data to the memory cell array, a data register for temporarily retaining the data read from and written to the memory cell array, synchronizing with the clock, and an echo signal generation circuit, synchronizing with the clock, for outputting an echo signal composed of a predetermined expected value pattern for notifying the outside of a data output with a delay time equal to a transmission delay time of the output data read from the memory cell array.