| 摘要 |
PURPOSE:To prevent the malfunction that the mode is switched to the test mode because of external pulse noise by switching the mode to the test mode by AND between a test level detection signal and a test permission signal which is based on the test level detection signal, a reset signal, and an internal reset signal. CONSTITUTION:A test permission flag generating circuit 4 is provided which takes a reset signal SR1, an internal reset signal SR2, and a test level detection signal S6 as the input and outputs a test permission signal S8. When the pulse noise higher than the test level is applied to an input terminal T1, the signal S6 is generated. However, the signal S6 is not continuously generated in the period from release of the signal SR1 to release of the signal SR2. Therefore, the circuit 4 is cleared at the time of release of the signal S6, and a test recognition signal S4 of the circuit 4 is kept cleared though the signal S6 is generated again, and a test signal S7 is not generated. Consequently, the malfunction of switching to the test mode is avoided though the external pulse noise is applied in the middle of normal operation. |
