To provide a writing circuit for a nonvolatile memory, a personal digital assistant and a data writing method for the nonvolatile memory capable of reducing electric power consumption when preventing a file system from being damaged.

This writing circuit 10 for the nonvolatile memory is provided with the nonvolatile memory 13, a CPU 11 for controlling only writing to the nonvolatile memory 13, and a main power source 14 and an auxiliary power source 15 for supplying power to the nonvolatile memory 13 and the CPU 11. The nonvolatile memory 13 is used partitioned into a file management area for storing file management information and a file storage area for storing file data. The power sources can be fed with power by the main power source 14 and the auxiliary power source 15, when writing the file management information in the nonvolatile memory 13, and power supply by the auxiliary power source 15 is stopped and the power is supplied by the main power source 14, when the file data are written in the nonvolatile memory 13.

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