3156B User Manual
Getting Started 1-22
Racal Instrument © 2005
Burst
The modulation burst mode is an extension of the triggered
modulation mode where the Model 3156B can be programmed to
output a pre-determined number of modulated cycles. The source to
trigger the counted burst cycle can be selected from a front panel
connector, VXI backplane trigger lines, or software command. Trigger
delay and re-trigger delay modes apply to the modulation burst run
mode.
Two conditions are required for the 3156B to output bursts of
modulated waveforms: 1) Output is on 2) Output is enabled by either a
software or hardware enable command.
Mixed Triggers
Mixed trigger run mode define a special sequence where the first
trigger source is accepted from a software command only and then
subsequent triggers are accepted from a hardware source only. In this
mode, trigger delay apply to the first software command only,
subsequent triggers will generate modulated waveforms without
delays.
Re-Trigger
The Re-trigger run mode requires only one trigger command to start a
sequence of triggered or counted burst of modulated waveforms. The
re-trigger delay defines the time that will lapse from the end of a
modulation cycle to the start of the next modulation cycle. Re-trigger
delay is programmable in steps of 20ns from 500ns to 21 seconds.
Re-trigger delay operates in conjunction with triggered and counted
burst modes only.
Four conditions are required for the 3156B to output modulated
waveforms in delayed trigger modulation run mode: 1) Output is on 2)
Output is enabled by either a software or hardware enable command
3) Re-trigger is on and 4) Re-trigger delay value is programmed.
Digital Patterns
Digital patterns are generated through a special front-panel connector,
one for each channel. Patterns are user programmable using 12-bit
hex words and are stored in pattern tables, as shown in the following
figure. The 3156B generates two pattern types: Free-run and
Stimulus. Both types are very similar except the free-run has hold time
parameter where each pattern can be designed with its own unique
hold time. Each channel has its own digital output. The digital lines are
differential, terminated into 50
Ω
to -2V.
Pattern update frequency is 100
μ
Hz to 100MHz and hold time can
vary from 1 to 10e9. The number of patterns a table can hold is 512k.