| 摘要 |
PURPOSE:To execute self-diagnosis in a short time even if the capacity of a memory device in large by executing reading and writing action at high speed through the use of a data reproducing function which is added to the memory device, logically comparing data read out by means of the reading action with an expected value, and executing self-diagnosis. CONSTITUTION:With using high speed write function, data for self diagnosis is written in an address area to be diagnosed. In such a case, data inverters 80A and 80B write data in respective address with the value inverted to '1' or '1' in respective address. If writing terminates, a read/write controller 50 is set in a data reproducing mode, and it executes the action of reproducing written data other address area. A logical comparator 100 compares having read data with the expected value and decides quality. If non-coincidence is detected, a failure generation address is transmitted to a test processor so as to display that the address is a failure. Thus, a diagnosing speed can considerably be increased, and the self-diagnosis can be terminated in a short time.
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