3156B User Manual
Racal Instrument © 2005
Using the Instrument 3-7
Selecting an
Output Enable
Source
An output enable command is necessary for the 3156B to start
generating waveforms at the output connectors. It is like a trigger
signal except it is not just used for triggered run mode; It is also
necessary to have an enable commands for run modes like
continuous. Note that the enable command has different meaning for
standard/arbitrary and modulated waveforms.
In standard waveforms mode, before an enable command is applied,
the output generates DC level, normally around the start of the
requested waveform. When an enable command is received, the
output generates the waveform. In continuous mode, the output is
continuous. In triggered or burst modes, the output resumes idle
position at the end of the signal.
In modulation functions, before an enable command is applied, the
output generates continuous CW (sinewave) at CW frequency. In
continuous mode, an enable command initiates continuous
modulation. In triggered or burst modes, the output resumes CW
frequency at the end of the modulating wave.
The enable signal can be applied to the 3156B from a number of
sources as described below:
Software
– defines an enable command is expected from a software
source
Hardware
– defines an enable command is expected from either a
front panel trigger input or from a backplane TTLTrg(n) signal. One of
these options is selected from the Trigger panel
Mixed
– defines a special enable command where the first enable is
software while hardware triggers are ignored and subsequent triggers
are hardware while software triggers are ignored.
Under some conditions, signals can be turned off at the output
connector, using the enable off command. Summary of run modes and
their respective enable and disable source is given in Table 3-2. Note
that in some cases different enable sources are used to turn the signal
on and off. The function call to disable the output is:
ri3156Bset_enable (0)
Also note that by using the enable off command, the output circuits are
still connected to the output connector and therefore, if you want to
assure high impedance at the output connector, use the following
command:
ri3156Bset_output (0)
