| 摘要 |
PROBLEM TO BE SOLVED: To enable specifying a defective place of a ROM holding secret of data incorporated in a ROM in a semiconductor integrated circuit in which a ROM with secret data stored is incorporated. SOLUTION: Data read out from a ROM 4 with secret data stored are ciphered by a ciphering circuit 5 using a key for test. And the data after ciphering are further ciphered by a second ciphering circuit 6, and the ciphered data are outputted from an external terminal. Also, when a defective place is specified, a program performing decoding of data is provided previously in a computer, it can be analyzed which bit of the ROM 4 is defective by decoding the data to a state before ciphering using the program. COPYRIGHT: (C)2004,JPO
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