Semiconductor integrated circuit and method of testing semiconductor integrated circuit
View Patent ↗Confidential CRC codewords are stored along with confidential data words on a ROM. A checker subjects one of the confidential data words, which has been read out from the ROM, to the same type of calculation as a predetermined calculation that was carried out to produce associated one of the confidential CRC codewords. A comparator compares a result of the calculation performed by the checker to the associated confidential CRC codeword that has been read out from the ROM.
1. A semiconductor integrated circuit comprising:
a ROM for storing plural confidential data thereon address by address which has no external direct input path and can be read only from an internal circuit inside of the integrated circuit;
a tester for testing the ROM address by address;
a storage device, which is included in the ROM, for storing plural redundancy check data address by address that have been obtained by performing a predetermined calculation on each of the corresponding plural confidential data, the plural redundancy check data an each of the corresponding plural confidential data being stored at mutually different addresses on the ROM;
a checker for performing the same calculation as the predetermined calculation on each of the plural confidential data that has been read out from the ROM address by address;
a comparator for comparing a result of the calculation performed by the checker to each of the corresponding plural redundancy check data stored in the storage device address by address; and
an address decoder which enables an operation of the comparator if an address is for the redundancy check data, and disables the operation of the comparator if the address is for the confidential data.
2. A method for testing a semiconductor integrated circuit including a ROM that stores plural confidential data thereon address by address and which can be read only from an internal circuit inside of the integrated circuit, the method comprising the steps of:
a. storing plural redundancy check data, which have been obtained by performing a predetermined calculation on each of the corresponding plural confidential data, in a redundancy check data storage device included in the ROM;
b. reading ou each of the plural confidential data from the ROM address by address and performing the same calculation as the predetermined calculation on each of the plural confidential data read out; and
c. reading out each of the corresponding plural redundancy check data from the storage device address by address and comparing a result of the calculation performed in the step b) to each of the corresponding plural redundancy check data read out,
wherein the plural redundancy check data and each of the corresponding plural confidential data are stored at mutually different addresses on the ROM,
and the comparison is enabled if an address is for the redundancy check data, and disabled if the address if for the confidential data.