CH Tech Pulse Generator - Manual (Page 23)

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4.4
TRIGGERED MODES OF OPERATION
The pulse stream can be programmed to run continuously, output a single function when
triggered, or output continuously as long as the gate (trigger in) is high (i.e., free run, trigger, or
gated repetition.). All three trigger modes are described below. The RUN control bit must be set
for any mode of operation to produce a pulse stream.
4.4.1 Free
When the FRE and RUN bits are programmed high, a continuous stream of pulses are generated
at the output driver. Both normal and special modes of operation function in the free run mode.
The triggered modes operate only with the FRE bit set to 0. Each pulse cycle will be
accompanied with a Trigger Out to indicate the beginning of the cycle.
4.4.2 Triggered Mode
When the FRE bit is reset (low) and the RUN bit is set (high), the output pulse stream function is
dependent on the TMD control bit. If TMD is reset (low) for triggered mode, an output pulse or
a double pulse is generated on each rising edge of the trigger pulse. Any triggers occurring prior
to the end of the pulse repetition interval are ignored, even if the pulse has finished. This allows
the pulse repetition interval to be used to hold off retriggering.
4.4.3 Gated Mode
When the FRE bit is reset (low) and the RUN bit is set (high), the output pulse stream function is
dependent on the TMD control bit. If TMD is set (high) for gated mode, the output pulse stream
performs like free run as long as the input gate (trigger in) is high. When the gate goes low, the
current pulse stream completes then stops. For square wave modes, the level remains at the
current level.
4.5
SPECIAL MODES OF OPERATION
Along with the normal modes of operation, three special free running square wave modes are
provided. These include a frequency programmable square wave and fixed frequency 20 MHz
and 40 MHz square waves. These modes provide a rapid method of producing a square wave
output. The square wave generation logic produces an output level change on each pulse
repetition interval. Note that this results in a square wave with a period equal to twice the
programmed PRI. The pulse width and delay time registers are disabled in this mode. In the 20
and 40 MHz modes the PRI, Pulse Width, and Delay time registers are disabled. Additionally, at
these high frequencies the output has limited output voltage capability; however,

5 Vpp can still
be sustained.