| 摘要 |
The invention provides a power-on circuit which assures a high impedance state of a terminal of an IC until the IC starts its operation after a point of time immediately after a power supply voltage is made available to the IC. The power-on circuit is built in a synchronous IC memory and includes a ring counter, an output controlling circuit, and a pulse signal interruption circuit. The ring counter successively generates a pulse signal after a power supply voltage begins to be supplied to the synchronous IC memory. The output controlling circuit controls an output terminal of the synchronous IC memory to a high impedance state while the pulse signal generated by the ring counter is inputted to the output controlling circuit. The pulse signal interruption circuit interrupts the pulse signal from being inputted to the output controlling circuit after a clock signal is inputted to the pulse signal interruption circuit.
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