| 摘要 |
PURPOSE:To automatically select a pulse generating circuit for low and high speed without an external selection signal by differentiating an input data signal with a clock signal so as to generate a high speed and a low speed pulse from positive and negative differentiating signals so as to identify whether the input clock signal is fast or slow automatically thereby selecting and outputting an object pulse. CONSTITUTION:A differentiating circuit 1 uses a clock signal to differentiate an input data signal, a low speed/high speed identification circuit 4 receives a clock signal at its data input terminal and receives a positive differentiating signal at its clock input terminal. A signal from a low speed pulse output circuit 2 is selected by a signal from a positive output terminal of the low speed/high speed identification circuit 4 and a signal from a high speed pulse output circuit 3 is selected by a signal from a negative output terminal of the low speed/high speed identification circuit 4 through the connection of a selection circuit 5. When the clock speed is high, the high speed pulse output circuit 3 is selected and when the clock speed is low, the low speed pulse output circuit 2 is selected. Thus, an object pulse is generated and outputted independent of whether or not the clock speed is high. |
