Memory device having high bus efficiency of network, operating method of the same, and memory system including the same

An operating method of a memory device for detecting data by selecting one of banks to which the same data is written, the operating method comprising:

• storing simultaneous write signal to indicate how many banks there are in which data are stored, in a write operation;
• performing a write operation to corresponding banks in response to the simultaneous write signal;
• selecting one of banks subjected to the write operation to perform a read operation and to store information on a read-out bank in a bank state storing unit;
• and
• selecting another bank instead of the read-out bank in the next read operation to perform the read operation.

A method of operating a memory device, the method comprising:

• enabling a first and second chip selection signals and a write command to select a first and second memory devices;
• simultaneously writing data to the first and second memory devices;
• and activating the first and second chip selection signals oppositely relative to a read command;
• and outputting data from the first and second memory devices successively to a data bus line.