| 摘要 |
A system clock generator includes circuitry for error-free switching of clock frequency. Frequency switching is necessary, for example, when the main power supply fails and to conserve standby battery energy the system is operated at a low clock frequency. Conversely, when the main power source is restored, system clock frequency must be returned to normal. The clock generator and switching circuitry comprise two bistable switch circuits and an RC (resistance-capacitance) oscillator made up of a NAND gate, an inverter, and an RC network. One of the bistable switch circuits includes means for detecting the presence of signals indicating the existence of a condition requiring frequency switchover.
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