Tektronix WFM5200 User Manual page 157

WFM5200 Waveform Monitor User Manual
The Serial (0H) setting, uses the methodology implied in appendix A of
SMPTE RP168. In this mode timing is considered to be zero when the 0H
sample of the serial stream aligns with the reference edge of the analog sync.
Note that this timing is actually at the scrambled interface which is slightly
different than timing to the parallel data into the serializer or the parallel data
out of the deserializer due to delays in those functions.
In the Relative to: Rear Panel mode, this 3 µs conversion delay is removed
from the measured offset before the display is generated. In the Relative to:
Saved Offset mode, it has no effect.
In the Relative to: Saved Offset mode, the timing of one signal is "saved"
and then that becomes "zero" for subsequent measurements. This removes
any need for a specific definition of zero timing, since the display shows the
difference in timing between the initial and current signals.
This timing relationship between input and reference is also compatible with
the waveform mode. That is, if you have zero timing on the Timing display
and change from internal to external reference, the displayed waveform will
not shift position.
NOTE.
If you have an input and reference combination that requires multiple
timing indicator circles, then it can be misleading to compare timing offsets
between multiple inputs. Because the timing display chooses the smallest of the
possible timing offsets, if a large timing difference exists between two inputs,
then they may not be matched. This problem also occurs using traditional timing
methods unless you use something similar to the SMPTE318 10 field flag to
identify a specific sub-multiple of the reference.
Application Example
141