a semiconductor memory device includes , in part , a first data i / o block and a second data i / o block . during a write operation , the first data i / o block transmits input data supplied through a first pad to a first global i / o line , and further generates a write internal signal . the second data i / o block transmits the write internal signal to a second pad in response to a monitor enable signal . during a read operation , the first data i / o block supplies data from the first global i / o line to a first pad , and further generates a read internal signal . the second data i / o block transmits the read internal signal to the second pad in response to a monitor enable signal .