Counter function blocks

Counters accumulate rising edges on their count inputs. The base types count with INT; typed variants (_INT, _DINT, _LINT, _UDINT, _ULINT) widen the preset PV and current value CV to the named integer type.

CTU — count up

Counts rising edges on CU. Q is TRUE when the count reaches the preset PV. R resets the count to zero. Typed variants: CTU_INT, CTU_DINT, CTU_LINT, CTU_UDINT, CTU_ULINT.

Direction	Name	Type	Meaning
Input	CU	BOOL	Count-up trigger (rising edge)
Input	R	BOOL	Reset
Input	PV	INT¹	Preset value
Output	Q	BOOL	TRUE when CV ≥ PV
Output	CV	INT¹	Current count

¹ PV/CV follow the typed variant: DINT for CTU_DINT, LINT for CTU_LINT, UDINT for CTU_UDINT, ULINT for CTU_ULINT.

FUNCTION_BLOCK CTU
VAR_INPUT
    CU : BOOL;
    R  : BOOL;
    PV : INT;
END_VAR
VAR_OUTPUT
    Q  : BOOL;
    CV : INT;
END_VAR
END_FUNCTION_BLOCK

VAR
    counter : CTU;
END_VAR

counter(CU := partDetected, R := resetBtn, PV := 10);
batchFull := counter.Q;     // TRUE once 10 parts counted
count := counter.CV;

CTD — count down

Counts rising edges on CD downward from the preset value. LD loads PV into CV. Q is TRUE when CV reaches zero. Typed variants: CTD_INT, CTD_DINT, CTD_LINT, CTD_UDINT, CTD_ULINT.

Direction	Name	Type	Meaning
Input	CD	BOOL	Count-down trigger (rising edge)
Input	LD	BOOL	Load preset into CV
Input	PV	INT¹	Preset value
Output	Q	BOOL	TRUE when CV ≤ 0
Output	CV	INT¹	Current count

¹ Width follows the typed variant, as for CTU.

FUNCTION_BLOCK CTD
VAR_INPUT
    CD : BOOL;
    LD : BOOL;
    PV : INT;
END_VAR
VAR_OUTPUT
    Q  : BOOL;
    CV : INT;
END_VAR
END_FUNCTION_BLOCK

VAR
    remaining : CTD;
END_VAR

remaining(CD := itemShipped, LD := reload, PV := 20);
empty := remaining.Q;        // TRUE once CV counts down to 0
left  := remaining.CV;

CTUD — count up/down

Combined up/down counter. Typed variants: CTUD_INT, CTUD_DINT, CTUD_LINT, CTUD_UDINT, CTUD_ULINT.

Direction	Name	Type	Meaning
Input	CU	BOOL	Count-up trigger (rising edge)
Input	CD	BOOL	Count-down trigger (rising edge)
Input	R	BOOL	Reset CV to 0
Input	LD	BOOL	Load PV into CV
Input	PV	INT¹	Preset value
Output	QU	BOOL	TRUE when CV ≥ PV
Output	QD	BOOL	TRUE when CV ≤ 0
Output	CV	INT¹	Current count

¹ Width follows the typed variant, as for CTU.

FUNCTION_BLOCK CTUD
VAR_INPUT
    CU : BOOL;
    CD : BOOL;
    R  : BOOL;
    LD : BOOL;
    PV : INT;
END_VAR
VAR_OUTPUT
    QU : BOOL;
    QD : BOOL;
    CV : INT;
END_VAR
END_FUNCTION_BLOCK

VAR
    stock : CTUD;
END_VAR

stock(CU := incoming, CD := outgoing, R := FALSE, LD := FALSE, PV := 100);
level := stock.CV;