Reference

Measuring Relative Timing

Between Two Serial

Component Signals

To measure the timing of two digital signals, use the following procedure:

1.Connect the two terminated SDI signals to be measured to Input A and Input B on the waveform monitor.

2.Select Input A to display on the waveform monitor.

3.Verify that the waveform monitor is externally referenced to a black burst or tri-level sync signal (as appropriate).

4.In the Video Inputs/Outputs submenu of the Configure menu, set Strip EAV/SAV to Pass. This mode allows the 3FF, 000, 000, and XYZ values to be displayed on the waveform monitor as shown in Figure 3-15.

NOTE. The transition from 3FF to 000 and 000 to XYZ produces ringing on the display when passed through the appropriate SD or HD filter. The SAV or EAV pulse can be used as a timing reference by positioning it on a major tick mark of the waveform graticule display and comparing it to the other SDI signals, ensuring that they are positioned at the same mark.

There are no vertical pulses in the digital domain; digital systems calculate their video position based on the values of F, V, and H. Therefore, a reference point must be defined in order to measure vertical timing. For simplicity, the first line of active video can be used as the reference, because the vertical blanking lines are normally blank.

5.To measure vertical timing, perform the following steps:

a.Set Line Select and Sweep for two-line mode.

b.Select Field 1 and set Line Select at the setting that will display the last line in the vertical interval and the first line of active signal (Input A).

The Line Select setting should be line 20 for 1080 Interlaced HDTV, 41 for 1080 progressive formats, 25 for 720 progressive, 19 for 525 interlace, or 22 for 625 interlace. If necessary, adjust the vertical timing of the signal source until the display is correct.

c.Select Input B and make sure the last vertical and first active lines are displayed. If necessary, adjust the vertical timing to align both vertical positions to the start of active video.

d.Switch back to Input A and set MAG to ON, noting the amplitude of the SAV pulses.

e.If the amplitudes of both pulses are identical, they are in the same field. If not, the two signals are in opposite fields and timing adjustments should be made to align the sources to the same starting point.

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WFM700 Series Waveform Monitors User Manual