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| What is the difference between UP Counter, DOWN Counter and UP/DOWN Counter? |
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As for UP Counter, increment the current value when the counter trigger bit CE turns ON, and turn ON the counter output bit when the current value reaches the preset value.
As for DOWN Counter, decrement the current value when the counter trigger bit CE turns ON, and turn ON the counter output bit when the current value is zero or less.
As for UP/DOWN Counter, you can select Up Counter or Down Counter by turning ON/OFF the counter up instruction UP. |
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| Special variables automatically created when creating counter |
| Special Variable |
Description |
Variable Type |
| Variable.PV |
Preset Value |
Integer |
| Variable.CV |
Current Value |
Integer |
Variable.R |
Counter Reset |
Discrete |
| Variable.UP |
UP Counter |
Discrete |
| Variable.QU |
UP Counter Output |
Discrete |
| Variable.QD |
DOWN Counter Output |
Discrete |
| Variable.Q |
Counter Output |
Discrete |
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| ・UP Counter |
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When the counter trigger bit CE passes power, the current value CV is incremented by one. When the current value CV is equal to the preset value CV, the counter output bit Q is turned ON, and the instruction passes power. |
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| ・DOWN Counter |
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When the counter trigger bit CE passes power, the current value CV is decremented by one. When the current value becomes equal to or less than zero after decrementing, the counter output bit Q is turned ON, and the instruction passes power. |
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| ・UP/DOWN Counter |
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When executing the CTUD instruction while the counter up instruction variable UP is ON, the execution is similar with the CTU instruction (up-counter).
When Variable. UP is OFF, the execution is similar with the CTD (down-counter) instruction.
After executing the CTUD instruction:
If the current value CV is equal to or greater than the preset value PV, Variable. Q and Variable. QU are turned ON.
If the current value CV is equal to or less than zero, the Variable. Q and Variable.QD are turned ON. |
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