| 摘要 |
PURPOSE:To simplify one oscillating circuit by using said oscillating circuit as a common oscillation source for the generation of a received sampling clock signal synchronized with a clock run-in signal and the generation of a display clock signal synchronized with a horizontal synchronizing signal. CONSTITUTION:A crystal oscillating circuit 22 oscillates at fixed frequency and one of its outputs is synchronized with a clock run-in signal through a clock run-in signal synchronizing circuit 24. The circuit 24 consists of a counter 42, inverters 43 and 44, NAND circuits 45 and 47, and a shift register 46, and a five-frequency-dividing circuit is reset where the oscillation output signal is put in phase with the clock run-in signal, thereby generating a signal of (8/5)fsc (color subcarrier frequency). The output of the oscillating circuit 22 is supplied to a synchronizing circuit 23 for horizontal synchronizing signal as well. This circuit 23 consists of D-FFs 48 and 49, NAND circuits 50 and 52, and a shift register 51 and in every horizontal scanning period, the five-frequency-dividing circuit is reset to generate a display clock signal of (8/5)fsc. Therefore, only one oscillating circuit is sufficient and all devices can be constitute with digital circuits. |
