Stanford Research Systems DS360 Operating Manual And Programming Reference page 48

3-14 Operation
computer interfaces. In addition, the output can be gated on and off from the
TRIGGER/GATE IN BNC, with TTL high setting the "ON" level and TTL low setting
the "OFF" level.
The current trigger source is indicated by an LED under the TRIGGER heading next to
the display. To view the current trigger source for modification, press the [SHIFT][TRIG
SRC] keys. To change the trigger source, use the spin knob or [>] right or [<] left cursor
keys.
During the "ON" time for bursts the TRIG' D (triggered) LED is lit. If a new trigger is
received during an external or single triggered burst the ERR LED will flash. Any
triggers received during an external or single triggered burst will be ignored. Trigger
errors only indicate that a trigger occurred during a burst; there is no effect on the output
waveform.
Sine and Square Wave Bursts
Internal Burst Rate
The burst rate is the total number of cycles in a burst, both the "ON" and "OFF" cycles,
when generating internally triggered bursts. It is set in integer number of cycles and can
range from 2 to 65535 (1 for the 1/2 cycle output. See below). In addition, it must be at
least one count greater than the Burst Count. To display the current burst rate, press the
[RATE] key. To modify the rate, type the new value in number of counts and press any
of the entry keys. Or use the spin knob to modify the displayed value. If an illegal value
is entered, the unit will beep, display " R ange Er " and flash the ERR LED. If a value
that is less than the current burst count is entered, the unit will beep, flash the ERR LED,
display " A djBur " (adjust burst), and adjust the Burst Count to one less than the Burst
Rate.
External Burst Rate
External or single triggered sine or square bursts are synchronized to the output zero
crossings. Because of this, there is an uncertainty of 0 to one cycle from the start signal
(from the TRIGGER IN, computer interface or front panel) and the actual beginning of
the burst. The BURST OUT BNC signal, which goes high at the beginning of the burst
should be used if it is necessary to synchronize the DS360 with an external device,
instead of the triggering signal. This limits the maximum rate that a burst can be
triggered externally (or singly) to somewhat less than for internally triggered bursts. To
never miss a trigger, the maximum external (or single) trigger rate is given by:
Bursts can be triggered somewhat faster than this if it is permissible to skip triggers.
Burst Count
The burst count is the number of "ON" cycles (or high level) in a burst. It is set in
integer number of cycles and can range from 1 to 65534. In addition it must be at least
one count less than the Count Rate. To display the current Burst Count, press the
[SHIFT][BURST CNT]. To modify the count, type the new value in number of counts
and press any of the entry keys. Or use the spin knob to modify the displayed value. If an
illegal value is entered, the unit will beep, display " R ange Er" and flash the ERR LED.
DS360 Ultra Low Distortion Function Generator
OutputFreq
<
ExtTrigFreq
BurstCount
+ 1