7.2.4 CTD_INT

Function

CTD_INT is called a down counter, used to accumulate the number of input pulses (0->1 or 1->0) at the input end.

LD graphics

Parameter description

Interface variables	Declaration	Data type	Description
CD	Var_Input	BOOL	Down counter input
PV	Var_Input	INT	Preset value
LD	Var_Input	BOOL	Load preset value, set CV to PV
Q	Var_Output	BOOL	Counter status, output bit
CV	Var_Output	INT	The value of the current count

Corresponding syntax

• Counting range: -32768~32767
• CD changes from FALSE to TRUE, CV decreases by 1;
• When CV is equal to 0, Q outputs TRUE. After that, whenever CD changes from FALSE to TRUE, Q keeps outputting TRUE, and CD continues to decrease by 1 until it reaches the minimum value of the integer type specified by the counter.
• At any time, as long as LD is TRUE, Q outputs FALSE, and CV immediately stops counting and returns to the PV value

warning

Function block usage requires global declaration of an instance

Example

• LD example is shown in the following animation:

• ST example is shown in the following code:

CTD_INT_1(
    CD:=DOWN,
    LD:=LOAD,
    PV:=1,
    Q=>OUT,
    CV=>cVar
);
IF OUT THEN
    iVar:=1;
    ELSE
        iVar:=0;
END_IF;