| 摘要 |
<p>PURPOSE:To adapt a drum trapezoid wave generating circuit to IC- implementation, to reduce a delay quantity in both EP and SP modes, and to stabilize servo characteristics by providing a 60Hz oscillation circuit, and switching threshold values set in the circuit according to the modes and obtaining a trapezoid wave signal. CONSTITUTION:A vertical synchronizing signal A is made into a count signal (c) by the 60Hz oscillation circuit 21. Threshold values C1, C2, C3, and C4 are set in the oscillation circuit 21 and a signal (d) is led out of a flip-flop 22 with the threshold value C1 to obtain a reset signal (e) through a reset pulse generating circuit 23. A signal (f), on the other hand, is led out of a flip-flop 24 with the threshold value C4 and a control pulse (g) is obtained by a control pulse generating circuit 4. In SP mode, a signal (h) is led out of a flip-flop 25 with the threshold value C3 an a trapezoid wave signal (i) is obtained by a trapezoid wave generating circuit 18. In EP mode, on the other hand, a signal h' is led out of the flip-flop 25 with the threshold value C2 of the oscillation circuit 21 and a trapezoid wave signal i' is obtained by the trapezoid wave generating circuit 18.</p> |
