Trigger generator and waveform monitor

摘要

A waveform monitor receives HDTV and SDTV signals that are provided to a channel and an external trigger terminal respectively. An HDTV signal processor 14 produces a reference clock PCLK from the HDTV signal. A counter starts counting at the vertical sync signal of the SDTV signal and generates a trigger every time the count of the reference clock PCLK reaches a predetermined number (2,200, for example). This allows generation of a trigger signal which is phase locked to the vertical sync signal of the SDTV signal, and of which the frequency is the same as the horizontal line frequency of the HDTV signal. Therefore the waveform monitor can display the HDTV waveform line by line even though the HDTV and SDTV signals have different numbers of lines per field. The waveform monitor can be used to measure phase difference between television signals of difference formats, such as the HDTV and the SDTV.