Advantech 3718HG, Руководство пользователя

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4 8 PCM-3718H/3718HG User's Manual
7.3 Counter Operating Modes
MODE 0 - Stop on Terminal Count
The output will be initially low when you set mode 0. After you load
the count into the selected count register, the output will remain low
and the counter will count. When the counter reaches the terminal
count, its output will go high and remain high until you reload it with
the mode or a new count value. The counter continues to decrement
after it reaches the terminal count. Rewriting a counter register during
counting has the following results:
1. Writing to the first byte stops the current counting.
2. Writing to the second byte starts the new count.
MODE 1 - Programmable One-shot
The output is initially high. The output will go low on the count
following the rising edge of the gate input. It will then go high on the
terminal count. If you load a new count value while the output is low,
the new value will not affect the duration of the one-shot pulse until
the succeeding trigger. You can read the current count at any time
without affecting the one-shot pulse. The one-shot is retriggerable,
thus the output will remain low for the full count after any rising edge
at the gate input.
MODE 2 - Rate Generator
The output will be low for one period of the input clock. The period
from one output pulse to the next equals the number of input counts
in the counter register. If you reload the counter register between
output pulses, the present period will not be affected, but the subse-
quent period will reflect the value.
The gate input, when low, will force the output high. When the gate
input goes to high, the counter will start from the initial count. You
can thus use the gate input to synchronize the counter.
With this mode the output will remain high until you load the count
register. You can also synchronize the output by software.