CTUD

The CTUD function block is an up and down counter.

If RESET = TRUE, the counter variable CV is initialized with 0. If LOAD = TRUE, the counter variable CV is initialized with the upper limit PV.
If the CU input has a rising edge from FALSE to TRUE, the counter variable CV is increased by one. If the counter variable CV reaches the value of the counter limit PV, the QU output is set to TRUE.
If the CD input has a rising edge from FALSE to TRUE, the counter variable CV is reduced by one as long as CV is greater than 0. If the counter variable CV reaches the value 0, the QD output is set to TRUE.

Inputs

VAR_INPUT
    CU    : BOOL; (* Count Up on Rising Edge*)
    CD    : BOOL; (* Count Down on Rising Edge*)
    RESET : BOOL; (* Reset Counter to 0 *)
    LOAD  : BOOL; (* Load Start Value *) 
    PV    : WORD; (* Start Value / Counter Limit *)
END_VAR

Name	Type	Description
CU	BOOL	On a rising edge: count up by one
CD	BOOL	On a rising edge: count down by one
RESET	BOOL	TRUE: Reset counter variable CV to the value 0
LOAD	BOOL	TRUE: Set counter variable CV to the start value PV
PV	WORD	Start value/counter limit

Outputs

VAR_OUTPUT
    QU : BOOL; (* Counter reached Limit *)
    QD : BOOL; (* Counter reached 0 *)
    CV : WORD; (* Current Counter Value *)
END_VAR

Name	Type	Description
QU	BOOL	TRUE if the counter value CV is greater than or equal to the counter limit PV.
QD	BOOL	TRUE if the counter value CV is 0.
CV	WORD	Counter variable (current counter value)

Requirements

Development environment	Target platform	PLC library to include
TwinCAT v3.0.0	PC or CX (x86)	Tc2_Standard