Semiconductor memory device having high data input/output frequency and capable of efficiently testing circuit associated with data input/output

Abstract

A data input/output circuit includes an S/P data conversion circuit which converts serial data input to a data terminal into a parallel data and transmits the parallel data to write data lines, a P/S data conversion circuit which converts parallel data on read data lines to serial data and outputs the serial data to the data terminal, and an input/output test circuit placed between the write data lines and the read data lines. The input/output test circuit responds to an input/output test signal to directly transfer data on the write data lines respectively to the read data lines without passing them through a memory cell array.