| 摘要 |
PURPOSE:To perform frame synchronization at the same timing as the case of positive polarity without the shift of the timing even when cable connection is reverse polarity in a transmission line using Manchester codes. CONSTITUTION:Reception data 21 from the transmission line are converted to unipolar data 23 in a code conversion circuit 11 and the extraction clock 24 of a frequency which is the double of the unipolar data 23 is obtained from a source clock 22 in a clock extraction circuit 12. By using it, the unipolar data 23 are outputted as parallel data 35 from a shift register 13 while being shifted by each bit and when one of frame synchronization pattern detection circuits 14 and 15 for simultaneously detecting both frames of the positive or reverse polarity of the cable connection detects the frame, a synchronization protective circuit 17 outputs synchronization establishment signals 32 at the timing from a timing generation circuit 16. Thus, a cable connection state is simultaneously recognized. |
