| 摘要 |
PURPOSE:To exclude a counter counting INIT signal intervals to reduce the scale of hardware by providing a differentiating (shift) circuit and an INIT detection circuit. CONSTITUTION:A differentiation (shift) circuit 68 receives an ICAR signal and a demodulator clock DEM CLK and generates a signal 1 of one bit width (one period of DEM CLK) and uses it as forward/backward protection counters 62, 64. In receiving the INIT signal, the forward protection counter 64 is loaded. The signal 1 is given to an INIT detecting circuit 60 and the said circuit 66 is set by the said signal 1 when the INIT signal comes just before the signal 1. Since the counter clock signal 1 appears just after the INIT signal, then the sweep tracking control signal S/T is changed immediately depending whether the INIT signal by protection stage number comes or does not come. |
