| 1. A card controller which writes data to a semiconductor memory having a first memory block and a second memory block each
including a plurality of nonvolatile memory cells each configured to hold at least 2 bits, data in the first memory block
and data in the second memory block being each erased at a time, the card controller comprising:
an arithmetic processing device which writes the data to the memory cells in the first memory block using an upper bit and
a lower bit of the at least 2 bits and writes the data to the memory cells in the second memory block using only the lower
bit of the at least 2 bits.
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