TOF

The TOF function block implements a timer with a switch-off delay.

If IN = TRUE, the Q output has the value TRUE and the ET output has the value zero. As soon as IN is set to FALSE, the time in milliseconds is counted up in ET until the setpoint PT is reached. Q is FALSE, if IN = FALSE and ET = PT. Otherwise Q = TRUE.

Graph showing TOF over time:

The TOF function block requires 15 bytes of data.

Inputs

VAR_INPUT
    IN : BOOL; (* starts timer with falling edge, resets timer with rising edge *) 
    PT : TIME; (* time to pass, before Q is reset *)
END_VAR

Name	Type	Description
IN	BOOL	Falling edge: Start timer Rising edge: Reset timer
PT	TIME	Delay time (time that elapses before Q is reset)

Name

Type

Description

BOOL

Falling edge: Start timer

Rising edge: Reset timer

TIME

Delay time (time that elapses before Q is reset)

Outputs

VAR_OUTPUT
    Q  : BOOL; (* is FALSE, PT seconds after IN had a falling edge *)
    ET : TIME; (* elapsed time *)
END_VAR

Name	Type	Description
Q	BOOL	TRUE if the IN input is TRUE. FALSE if the IN input is FALSE and the time specified in PT has expired.
ET	BOOL	Elapsed time since the falling edge at the IN input.

Name

Type

Description

BOOL

TRUE if the IN input is TRUE.

FALSE if the IN input is FALSE and the time specified in PT has expired.

BOOL

Elapsed time since the falling edge at the IN input.

Requirements

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