Semiconductor storage device, method for controlling the same and control program

A method of controlling a semiconductor storage device comprising a semiconductor memory comprising blocks including memory cells, and a memory controller, the method comprising:

• in a first mode, for each of the blocks, autonomously erasing data, writing data, and reading the written data to determine that the block or the semiconductor storage device is defective when a count of errors in the read data exceeds a correction capability or a threshold of the memory controller;
• in a second mode,
• writing substantial data and redundant data for correcting an error in the substantial data in the semiconductor memory,
• reading substantial data and corresponding redundant data from the semiconductor memory, correcting an error in the read substantial data in accordance with the read redundant data,
• when error correction of substantial data read from the semiconductor memory fails, reading the substantial data which failed in the error correction using a read level shifted from the present read level;
• and
• writing in the semiconductor memory a program which causes the memory controller to operate in the first mode or a program which causes the memory controller to operate in the second mode, or writing in the semiconductor memory a program which causes the memory controller to operate in a selected one of the first and second modes.

A control program for a memory controller in a semiconductor storage device which comprises a semiconductor memory comprising blocks including memory cells and the memory controller, the program causing the memory controller to cause the semiconductor memory to:

• write substantial data and redundant data for correcting an error in the substantial data in the semiconductor memory,
• read substantial data and corresponding redundant data from the semiconductor memory, and
• correct an error in the read substantial data in accordance with the read redundant data,
• when error correction of substantial data read from the semiconductor memory fails, read the substantial data which failed in the error correction using a read level shifted from the present read level,
• wherein when written in the semiconductor storage device, the program causes the memory controller to enter a first mode in which the memory controller, for each of the blocks, autonomously erases data, writes data, and read the written data, and determines that the block or the semiconductor storage device is defective when a count of errors in the read data exceeds a correction capability or a threshold of the memory controller.