| 摘要 |
PURPOSE:To shorten a pull-in time at the time of switching a reference clock by initializing a counter part and a phase comparing part by an initializing pulse at the time of inputting a switching pulse, and starting an operation at the back changing point of the initializing pulse. CONSTITUTION:At the time of switching a reference signal impressed on a phase comparing part 2 to the other reference signal, a switching information pulse is inputted to an initializing pulse preparing means 5, the initializing pulse whose pulse width is longer than that of the other reference signal, and whose back changing point is matched is prepared, and transmitted to the load terminals of count parts 3 and 4, and a phase comparing part 2. The corresponding load values are loaded at the count parts 3 and 4, the phase comparing part 2 is initialized, the operation is started at the back changing point of the initializing pulse, the operation of the count parts 3 and 4 is started, and an N frequency-division signal is prepared at the changing point of the other reference signal. Thus, the pull-in time at the time of switching the reference signal can be shortened. |
