A method of a flash memory controller coupled between a flash memory and an electronic device is provided. The flash memory has a plurality of blocks each having a plurality of pages. The method includes: detecting whether a data unit is formed by a repeated pattern, the data unit being transmitted from the electronic device and to be written into the flash memory or the data unit being read from the flash memory; and making a record of the repeated pattern at a field of the specific table if determining that the data unit is formed by the repeated pattern.
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