Chapter4 HardwareOverview
©NationalInstruments Corporation 4-15 NI5102 User Manual
Analog TriggerCircuit
The NI 5102 contains a sophisticated analog trigger circuit that accepts
boolean outputs from level comparators and makes intelligent decisions
about the trigger. Several triggering modes are available, including edge,
window, and hysteresis. For information on configuring trigger functions,
seet he Triggering Functions and Parameters section in Chapter 3,
Common Functions and Examples, of your NI-SCOPE Software User
Manual.
TriggerHold-off
Triggerhold-off is the l ength of time that the NI 5102 waits after finishing
anacquisition before it may accept another trigger. Hold-off is provided in
hardwareusi ng a2 4-bit down counter clocked by a 2.5 MHz internal
timebase.With this configuration, you can select a hardware hold-off value
of8 00 ns to 6.71 si n increments of 400 ns.
Whenan acquisition is in progress, the counter is loaded with a digital value
thatcorresponds to the desired hold-off time. The End of Acquisition signal
triggersthe counterto start counting down.Before the counter reaches its
terminalcount (TC), all triggers are rejected in hardware. At TC, the
hold-offcounter reloads the hold-off value and prepares to accept the next
trigger.Figure 4-11 shows a timing diagram of signals when hold-off is
enabled.