| 摘要 |
PURPOSE:To facilitate the test of the refreshing function of a pseudo static RAM by connecting plural diode-connected MOSFETs between an external terminal and a grounding electrode, and deciding a voltage input which is higher than usual. CONSTITUTION:A write voltage to the pseudo static RAM is outputted through an inverter I1 forming a buffer responding to a normal binary input voltage from an input terminal P1. Then, N channel diode-connected MOSFETs T1- T8 are connected in series between the terminal P1 and ground by connecting a gate and a drain and when the voltage applied to the terminal P1 becomes higher than usual exceeding the sum of threshold values of the FETs T1-T8, the high input voltage is detected through inverters I2 and I3. Then, a refresh counter is reset with a detection voltage phireset. Thus, the refresh counter is reset without turning off the power source and the test of the refreshing function of the pseudo static RAM is taken easily. |
