| 摘要 |
PROBLEM TO BE SOLVED: To solve a problem of conventional methods that the conventional method diagnosing a failure of a bit of an address area cannot find a failure of an address line to a memory and that the conventional method detecting the failure of the address line requires a long time in diagnosis because the conventional method is executed in addition to a diagnostic process of the failure of the bit of the address area. SOLUTION: Test data AAAAh is written into addresses 55h and AAh of a memory 1, and the test data 5555h is written into other addresses. Data are sequentially read from the memory 1. When the address is 55h or AAh, the test data S3 are changed over to AAAAh. When the address is not 55h or AAh, 5555h is selected as the test data S3. When a failure occurs in a state that a bit 7 is fixed to zero, the test data S3 of AAAAh is overwritten into an address 2Ah because the address AAh becomes 2Ah. When reading the data of the address 2Ah, the data AAAAh are outputted and disagree with expected value of 5555h. Thereby, a disagreement signal S7 is outputted from a comparison coincident circuit 11. |
