| 摘要 |
PURPOSE:To cope with a change in the software of the vertical synchronizing frequency of a using signal source by feeding a latch pulse, a reset pulse respectively to a latch circuit, a counter by a one shot multivibrator operated by a vertical synchronizing signal. CONSTITUTION:When the vertical synchronizing signal A is inputted to the one shot multivibrators 41, 42, the latch pulse C is outputted to the latch circuit 2 from an output terminal 4d in the timing of a leading edge and the counted output of a horizontal synchronizing signal B by the counter 1 is latched by the latch circuit 2. Then, the reset pulse D is outputted to the counter 1 from an output terminal 4c in the timing of the trailing edge of the vertical synchronizing signal A, the counter 1 is reset and the counting of the horizontal synchronizing signal B is started from zero again. Only when the level of the latch pulse C is changed from a low level to a high level, the latch circuit 2 fetches data and only when the counted result of the counter 1 changes, the output of the latch circuit 2 is changed.
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