Nematron Pointe Controller - Manual (Page 357)

Pointe Controller User Guide Appendix C: Ladder Diagram Block Reference
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Param Name Config Var Type Description
CV Counter
Value req %QUD
%MUD
The current value of the counter.
C.2.5 Counter, Down (CTD)
When used in a Ladder Diagram, the CTD block decrements a counter by 1. It also
sets a “done bit when the counter reaches 0.
Select the tool (from the Timers and Counters Blocks toolbar) and click on a
ladder rung to insert the following block:
Once the block is inserted, you can double-click on it to configure it.
Functional Description
This block always passes the Enable input state (EN) through to the Enable Out
output state (ENO) without change; when EN becomes on, ENO is turned on, and
when EN becomes off, ENO is turned off.
When EN becomes on, the block function is executed and the following
conditions are evaluated in order:
1. If the Preset input (L) is true, then the Counter Value output (CV) is reset
to the Preset Value input (PV).
2. If L is false and the Count Down input (CD) is true, then CV is
decremented by 1.
3. If CV is less than or equal to 0, then the Output Down bit (QD) is set to
true. If CV is greater than 0, then QD is set to false.
The block function is executed every time the ladder is scanned , so long as EN
remains on.
NOTE: Because the frequency of the count is based on the project’s Scan Interval ,
it should not be used to gauge real time. To gauge real time, use a Timer .