| 摘要 |
PURPOSE: To generate an alarm signal in the case where step-out occurs in spite of small circuit scale and in addition, a simple configuration in a transmitting device such as a clock controlled synchronizing device, etc. CONSTITUTION: A frequency-divided input signal obtained by frequency-dividing an input signal fin by an input frequency divider 16 and a frequency-divided output signal obtained by frequency-dividing an output signal fout by an output frequency divider 14 are phase-compared by a phase comparator 11, and control voltage to control a voltage controlled oscillator 13 is outputted. At that time, an input clock is inputted to a window generator 17 too, and a window to show step-out tolerance to the leading edge of the frequency-divided input signal is generated. By referring to this window, whether the leading edge of the frequency-divided output signal is inside the window or not in a flip flop 18 is judged. When the leading edge of the frequency-divided output signal is inside the window, it is judged that synchronization is kept, and when it is outside the range of the window, it is judged that the step-out has occurred, and a step-out alarm is outputted. |
