Memory device, operating method of the same, and memory system

A method of operating a memory device, comprising:

• receiving a data strobe signal transmitted by an external controller through a DQS pin, the data strobe signal having M levels, where M is a natural number greater than 2;
• and
• decoding the data strobe signal and restoring data that is encoded into the data strobe signal by the external controller,
• wherein the data strobe signal is a signal swinging based on an intermediate level between a minimum level and a maximum level among the M levels.

A memory device comprising:

• a buffer configured to receive a multilevel signal having M levels through a DQS pin, where M is a natural number greater than 2;
• a delay circuit configured to generate a delayed clock signal by delaying the multilevel signal;
• a first sense amplifier configured to generate a first output signal based on the multilevel signal and a first reference signal at a rising edge and a falling edge of the delayed clock signal;
• a second sense amplifier configured to generate a second output signal based on the multilevel signal and a second reference signal greater than the first reference signal at the rising edge and the falling edge of the delayed clock signal;
• and
• a decoder configured to restore at least one of DBI data, DM data, CRC data, or ECC data that is encoded into the multilevel signal, using at least one of the first output signal or the second output signal.