Semiconductor device and diagnosis method thereof

A method of diagnosing a semiconductor device comprising a non-volatile memory storing a first user data and a first value fixed data and a Built In Self Test (BIST) circuit for diagnosing the non-volatile memory,

• wherein the BIST circuit includes:
• a reading circuit that sequentially generates addresses and sequentially issues reading commands including the generated addresses to the non-volatile memory,
• a compressor that compresses the first user and the first value fixed data sequentially read from the non-volatile memory, in response to the reading commands from the reading circuit, according to a predetermined compression algorithm to output a first signature value, and
• a judgment circuit that judges whether or not a first fixed value agrees with the first signature value,
• wherein the non-volatile memory includes a first address space formed by addresses continuously read, with a generation sequence of the addresses by the reading circuit as a reference and storing the first data, and a first reservation address formed by a single or a plurality of addresses, read after the first address space, and storing the first value fixed data,
• the method comprising the following steps of:
• (1) calculating the first value fixed data using first user data wanted to be stored in the first address space;
• (2) storing the first user data in the first address space and storing the first value fixed data in the reservation address;
• (3) starting up the BIST circuit to obtain the first signature value;
• and
• (4) judging whether or not the first fixed value agrees with the first signature value obtained by Step (3),
• wherein when the first user data and the first value fixed data are compressed according to the predetermined compression algorithm with a predetermined initial value, the first value fixed data is data previously calculated such that the first signature value agrees with the first fixed value, and
• wherein when the first user data is rewritten to a second user data, the first value fixed data is rewritten to a second value fixed data, the compressor compresses the second user data and the second value fixed data to output a second signature value, the judgment circuit judges whether or not the first fixed value agrees with the second signature value, and the second value fixed data is data previously calculated such that the second signature value agrees with the first fixed value.