Semiconductor memory device and refresh control method

Abstract

A semiconductor memory device executes a refresh operation on memory banks, and includes: a command decoder that decodes a command from outside the semiconductor memory device, and outputs a refresh instruction when the command is an auto-refresh command; a refresh command generating unit that outputs a refresh command signal by a predetermined number of times corresponding to the number of word lines to be refreshed in response to the refresh instruction; a bank address counter that holds a bank address for selecting a memory bank to be refreshed, counts up the bank address every time the refresh command signal is output, and performs a carry-over action when count-up operations equivalent to the number of the memory banks are performed; and a row address counter that holds a row address for selecting a word line to be refreshed, and counts up the row address in response to the carry-over action.