A memory device includes a memory cell array and a data input/output circuit. The memory cell array includes a plurality of memory cells connected to a plurality of bit lines and a plurality of word lines. The data input/output circuit is configured to receive data from external data pins of the memory device, output the received data to the memory cell array through a plurality of input/output lines electrically coupled to the plurality of bit lines, receive data read from the memory cell array through the plurality of input/output lines, and output the read data through the external data pins. For each external data pin, the data input/output circuit is configured to output data received at the external data pin to a corresponding input/output line. The corresponding input/output line is selected in response to bit values of a set of bits included in the received data.