HP 54620A User's And Service Manual page 137

Ensuring Accurate Measurements
Time base and Acquisition
The range of available delay is different with negative delay values. Suppose
you set the time reference to Right, at a sweep speed of 5 ms, with a delay
value of -80 µs, and you perform a single acquisition. The display would look
like the following:
Figure 40
The time reference
is set to Right
The trigger point is
off-screen to the right
due to negative delay
Single Acquisition, Time Reference Right, Negative Delay of 80 µs
136