CTD

Counts (integers) from a given value down to 0 in increments of 1.
IMPORTANT: The CTD block does not detect the rising edges or falling edges of the counting input (CD). The block must be associated with an "R_TRIG" or "F_TRIG" block to create a pulse counter.
lrsb_ctd1
Arguments
CD
BOOL
Counting input
(down-counting when CD is TRUE)
LOAD
BOOL
Load command (dominant)
(CV = PV when LOAD is TRUE)
PV
DINT
Programmed initial value
Q
BOOL
Underflow: TRUE when CV <= 0
CV
DINT
Counter result
Example
(* FBD program using the CTD block *)
lrsb_ctd2
(* ST Equivalence: We suppose F_TRIG1 is an instance of F_TRIG block and CTD1 is an instance of CTD block*)
F_TRIG1(command);

CTD1(F_TRIG1.Q,load_cmd,100);

underflow := CTD1.Q;

result := CTD1.CV;
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