There is disclosed a memory system including a memory cell array, a sense amplifier circuit, a write circuit, a level setting circuit, a column decoder, a data line, and a sense amplifier control circuit. The method comprises using plural kinds of application voltage waveforms different in light emission luminance, as pulse voltages for sustain discharges in display of each sub-field, and adjusting the number of waves in each of the plural kinds of application voltage waveforms according to the weight of luminance set for each sub-field, thereby performing gradation display. In some embodiments, the device may further include a first memory device operative to look up a second data value based on the first data value, where the second data value is a representation of the first data value encoded according to an encoding scheme that allows clock recovery, and where the memory device is operative to be configured according to a plurality of line encoding schemes. An optional metalloid may be included in the solution.