| 摘要 |
PURPOSE:To increase the detecting range of faults with a detecting circuit and to ensure the conversion of the detecting circuit into an IC, by detecting the base potentials of two transistors for drive of writing current and using the detection output of said base potential and a write gate signal to perform a logical operation. CONSTITUTION:A fault detecting circuit 23 consists of an exclusive OR circuit 7, voltage comparators 181 and 182, a 3-input NOR gate 19, an AND gate 20, an NOR gate 21, a signal line 22 for threshold voltage, etc. Both outputs of the comparators 181 and 182 are set at low or high levels owing to a fault of earth, etc. with write data lines 11 and 12. In such a case, the output of the circuit 7 is set at a low level. Then the output of an AND gate 20 is also set at a low level. While the output of an inverter circuit 17 which feeds the potential of a write gate line 9 is set at a high level, and therefore the output of the gate 19 is set at a low level. Therefore both outputs of the gates 20 and 19 are fed to change the output of the gate 21 to a high level. Thus a fault can be detected. |
