Patent ID: 7558113

Claim:
A data writing method for use with a memory system including a NAND flash memory and a controller which controls the NAND flash memory, in which data inputted from a host is stored in the NAND flash memory, the data writing method comprising: carrying out a program operation to write data to a page of the memory cell array; carrying out a verify-read operation of the written data; judging based on a result of the verify-read operation whether or not failure occurs in writing data in any of the bits of the page; judging, if it is judged that failure occurs in writing data in any of the bits of the page, whether or not the number of failed bits of the page is within a predetermined allowable number; setting, if it is judged that the number of failed bits of the page is within the predetermined allowable number, a status of Pass in a pseudo manner, ending the write operation and issuing a Ready signal; and issuing a status read command from the controller to the NAND flash memory, upon receipt of the Ready signal, to determine whether the status is Pass or Fail.