| 摘要 |
PURPOSE:To easily change over vertical synchronizing signal by selecting the vertical synchronizing signal according to the presence or the absence of the vertical synchronizing signal formed by a vertical synchronizing signal generating circuit or the level of the vertical synchronizing signal obtained from a compositive video signal. CONSTITUTION:When taking out the vertical synchronizing signal 8 from a horizontal and vertical synchronizing signal 1, a change over circuit 3 are connected to a (a) side, and when taking out the vertical synchronizing signal 8 from the vertical synchronizing signal 5 (called VH hereinafter) formed from the vertical synchronizing signal generating circuit, the change over circuit 3 is connected to a (b) side. When an input voltage of a level detection circuit 4 is below 2.5V, the change over circuit 3 is connected to the (a) side and when it is above 2.5V, the change over circuit 3 is connected to the (b) side. According to the presence or the absence or the level of the VH, the selection of the vertical synchronizing signal from different sources is carried out. Thus, the change over circuit can be operated by the VH, so that in forming a semiconductor integrated circuit, the number of terminals is not increased.
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