Memory and memory system for periodic targeted refresh

A memory comprising:

• a plurality of word lines;
• a target address generation unit configured to generate one or more target addresses by using a stored address;
• and
• a control unit configured to sequentially refresh a plurality of first word lines in response to a refresh command that is periodically inputted, with a target refresh operation of refreshing a second word line corresponding to the target address when the first word lines are refreshed a reference number of times, and sequentially refresh the plurality of word lines without the target refresh operation in a self-refresh mode in which the refresh command is not inputted.

A memory system comprising:

• a memory controller configured to periodically generate a refresh command, and generate a self-refresh entry command for entering a self-refresh mode and a self-refresh exit command for exiting the self-refresh mode, wherein the refresh command is not generated in the self-refresh mode;
• and
• a memory including a plurality of word lines and an address generation unit for generating one or more target addresses by using a stored address, and configured to enter and end the self-refresh mode in response to the self-refresh entry command and the self-refresh exit command, respectively,
• wherein the memory is configured to sequentially refresh a plurality of first word lines in response to the refresh command, sequentially refresh the plurality of first word lines in the self-refresh mode in which the refresh command is not inputted, and refresh a second word line corresponding to the target address when the first word lines are refreshed a reference number of times only in response to the refresh command.