Reference
After the A trigger event is recognized, the oscilloscope b egin s cou nting
B trigger even ts. However, for the first B event to be counted, that
event must c on sist of both an opposite-polarity edge and the edge that
is counted. The opposite-polarity edge must occur ≥ 5nsaftertheA
trigger arming event. If this condition is not met, the oscilloscop e does
not count the first event, which results in a trigger on the n+1
st
event.
Refer to the next figure, where n =3 and A and B trigger slopes are set
to rising edge.
112 TDS3000C Series Oscilloscope User Manual