Importance

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Abstract

In a self-repairing operation, a first self-test of a RAM is performed at a first temperature to obtain a first RAM test result, a RAM built-in self-test circuit judges according to the first RAM test result that a faulty portion exists in the RAM, an LSI built-in self-repair circuit judges that the repair of the faulty portion of the RAM is possible, the LSI built-in self-repair circuit controls a redundancy control circuit to avoid the use of the faulty portion of the RAM in a normal operation, the temperature of the RAM is risen by operating the RAM or a logical circuit in a pseudo-self-test to change the first temperature to a second temperature, a second self-test of the RAM is performed at the second temperature to obtain a second RAM test result, and the LSI built-in self-repair circuit confirms that the repair of the faulty portion of the RAM is possible at each of the first and second temperatures by comparing the second RAM test result with the first RAM test result. Therefore, the reliability of the test of the RAM for the test condition change can be improved, and a correct operation of the RAM can be guaranteed at the first and second temperatures after a self-repair of the RAM.

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First Claim