US Patent 7558134 Semiconductor memory device and its operation method

A semiconductor memory device includes a memory-cell array, a read bit line, a write bit line, a sense amplifier, a first sense line, a second sense line, a first bit line switch, and a second bit line switch. The memory-cell array is laid out to form an array. The read bit line is shared by plural memory cells and connected to a data output node. The write bit line is shared by plural memory cells and connected to a data input node. The sense amplifier is configured to sense a difference in electric potential. The first sense line is connected to one of the input terminals. The second sense line is connected to the other input terminal. The first bit line switch is configured to control electrical connection and disconnection. The second bit line switch is configured to control electrical connection and disconnection.