3156B User Manual
Getting Started 1-8
Racal Instrument © 2005
Continuous
In normal continuous mode, the selected waveform is generated
continuously at the selected frequency, amplitude and offset. Two
conditions are required for the 3156B to output waveforms in
continuous run mode: 1) Output is on and 2) Output is enabled by
either a software or hardware enable command. The waveform at the
output connector can be stopped (only on the last point of the
waveform) with a software enable off command. Chapter 3 lists the
various options of enabling and disabling the output waveform in the
various run modes and enable sources.
Triggered
In triggered mode, the Model 3156B circuits are armed to generate
one output waveform. The trigger circuit is sensitive to transitions at
the trigger input. Select between positive or negative transitions to
trigger the instrument. You may also program the trigger level to the
desired threshold level. When triggered, the generator outputs one
waveform cycle and remains idle at the last point of the waveform.
Two conditions are required for the 3156B to output waveforms in
triggered run mode: 1) Output is on and 2) Output is enabled by either
a software or hardware enable command.
The Model 3156B can be triggered from a number of sources: trigger
signal from a front panel connector, trigger signal on one of the VXI
backplane TTLTRG<n> or software trigger.
The trigger signal, whether it comes from the front panel or from the
VXIbus, is routed through some electrical circuits. These circuits
cause some small delay known as system delay. System delay cannot
be eliminated completely. It is, however, minimized in the Model
3156B to approximately 150ns. System delay is a factor that must be
considered when applying a trigger signal. It defines how long it will
take from a valid trigger edge to the moment that the output reacts.
Delayed Trigger
The delayed trigger run mode is exactly the same as the trigger mode
except a programmable delay inhibits signal output for a
programmable period after a valid trigger. The delay time defines the
time that will lapse from a valid trigger (hardware or software) to
output. The delay is programmable in steps of 20ns from 500ns to 21
seconds. The trigger delay can be applied to all run modes:
continuous, trigger and burst. Delayed trigger does not affect the
gated run mode.
Four conditions are required for the 3156B to output waveforms in
delayed triggered run mode: 1) Output is on 2) Output is enabled by
either a software or hardware enable command 3) Delayed trigger is
on and 4) Delay value is programmed.