| 摘要 |
PURPOSE:To control a stable vertical screen position even if an input video signal is a non-standard signal by measuring time per frame of the video signal, outputting it as a reference delay time control signal, conducting an operation with a scroll data signal and controlling the delay time of a vertical synchronizing signal. CONSTITUTION:A one frame time judgement circuit 4 counts the number of lines per frame and judges time per frame by the vertical synchronizing signal VD fetched by a synchronizing separator circuit 1. An averaging circuit 5 averages time per frame and outputs it to a control circuit 6 as the reference delay time control signal. The circuit 6 controls the output of the circuit 5 so that it becomes the reference delay time of a VD delay circuit 2. The circuit 6 operation-processes the reference delay time control signal and the scroll data signal and controls the delay time of the circuit 2. Reference delay time corresponding to time per frame is variably set, and the phase of VD' and that of an input signal are prevented from being deviated. |
