| 摘要 |
PURPOSE:To reduce a circuit scale and to improve stability and reliability by constituting an AFC circuit adjusting the period and the phase of an internal synchronizing signal to those of an external synchronizing signal by means of the comparison result of the period and the phase of the external synchronizing signal with a digital circuit so as to make the AFC circuit into LSI. CONSTITUTION:The external synchronizing signal is inputted to an input part 22, and an internal synchronizing signal generation part 16 generates the internal synchronizing signal. A phase/synchronism comparison control part 24 samples the external synchronizing signal at prescribed intervals, detects a period difference and a phase difference with the internal synchronizing signal so as to measure the degree. A decoder control part 30 and a control decoder 14 gradually change the period and the phase of the internal synchronizing signal based on the comparison result of the control part 24, and adjust the periods and the phases of the both synchronizing signals. When the periods of the both synchronizing signals become the same, a period value latch part 28 fixes the period of the internal synchronizing signal. Thus, the AFC circuit is realized by the digital circuit and it is made into LSI. The circuit scale is reduced and stability and reliability are improved. |
