Counter Operating Modes - Advantech PCM-3718 Series User 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 out-
put 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 fol-
lowing 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 follow-
ing 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 succeed-
ing 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 subsequent 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.
PCM-3718 Series User Manual
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