Patent ID: 8050083

Claim:
A write method of a phase change memory device, the method comprising: setting a write mode as one of a volatile write mode and a non-volatile write mode; writing data as volatile or non-volatile on a phase change memory cell of the phase change memory device by applying a write pulse corresponding to the write mode, the write pulse provided in the phase change memory cell being determined to be a write reset pulse or a write set pulse in accordance with the data value to be written, wherein writing data includes: writing non-volatile data in the non-volatile write mode by applying a first write pulse, and writing volatile data in the volatile write mode by applying a second write pulse, the first write pulse and the second write pulse are determined to both be the write reset pulse or the write set pulse in accordance with the data value to be written, and the second write pulse having a shorter width than the first width pulse, wherein, when power is not supplied to the phase change memory device the non-volatile data is retained and the volatile data is not retained; monitoring a capacity of a battery, the battery configured to supply power to the phase change memory device; and rewriting written volatile data as non-volatile data when the capacity of the battery is below a predetermined level.