In order to perform easily power cutoff of a device configuring a data processing system and to improve the power reduction effect at standby, the data processing system is configured with a microcontroller, a memory IC including a nonvolatile RAM array, and a power supply unit capable of controlling the power supply to the microcontroller and the memory IC, separately. When a control signal to control read and write of data to the nonvolatile RAM array is at a high level, the memory IC is enabled read and write of data to the nonvolatile RAM array. When the control signal is at a low level, the memory IC is disenabled read and write of data to the nonvolatile RAM array. The microcontroller sets the control signal at a low level, when the memory IC is shifted to a standby state by the power supply unit.