Keithley DAS-8 Series User Manual page 44

• Square-wave generator (Mode 3) — This mode is useful for
square-wave generation. The output is initially high. A trigger loads
the initial count value into the counter. At the next clock pulse after
the trigger, the counter starts counting down. When half the initial
count has elapsed, the output goes low for the remainder of the count.
When the total count elapses, the counter is reloaded with the initial
count value, the output goes high again, and the process repeats. If the
initial count is odd, the output is high for (n + 1) / 2 counts and low
−
for (n 1) / 2 counts, where n indicates the loaded count.
A high gate input enables counting; a low gate input disables
counting. If the gate goes low while the output is low, the output is set
high immediately. This allows you to use the gate input to
synchronize the counter.
Figure 2-9 illustrates square-wave generator mode.
Clock pulse
Trigger loads initial count
value of 4
Output
4
Figure 2-9. Square-Wave Generator Mode
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