Advantech PCI-1713, Руководство пользователя

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40 PCI-1713 User's Manual
MODE 3 – Square Wave Generator
This mode is similar to Mode 2, except that the output will remain
high until one half of the count has been completed (for even
numbers), and will go low for the other half of the count. This is
accomplished by decreasing the counter by two on the falling edge of
each clock pulse. When the counter reaches the terminal count, the
state of the output is changed, the counter is reloaded with the full
count and the whole process is repeated.
If the count is odd and the output is high, the first clock pulse (after
the count is loaded ) decrements the count by 1. Subsequent clock
pulses decrement the count by 2. After time-out, the output goes low
and the full count is reloaded. The first clock pulse (following the
reload) decrements the counter by 3. Subsequent clock pulses decre-
ment the count by two until time-out, then the whole process is
repeated. In this way, if the count is odd, the output will be high for
(N+1)/2 counts and low for (N-1)/2 counts.
MODE 4 –Software-Triggered Strobe
After the mode is set, the output will be high. When the count is
loaded, the counter will begin counting. On terminal count, the output
will go low for one input clock period then go high again.
If you reload the count register during counting, the new count will be
loaded on the next CLK pulse. The count will be inhibited while the
GATE input is low.
MODE 5 – Hardware-Triggered Strobe
The counter will start counting after the rising edge of the trigger
input and will go low for one clock period when the terminal count is
reached. The counter is retriggerable.