SF_TOF (FB)

Description of the function block

Tip

The version of the function block as described here corresponds to the latest version of the function block in Version list of function blocks.

Tip

SF_TOF is a timer function block from the SafetyStandard library. It is an extension of TOF, a standard IEC 61131-3 function block. The SF_TOF function block contains both standard data types and safety-oriented data types (prefix: SAFE).

SF_TOF is a timer block from the SafetyStandard standard library that implements a switch-off delay.

If the IN input changes from TRUE to FALSE, then the output also changes to FALSE, but only after the expiry of the delay time.

Figure 117. Function block: SF_TOF

Table 99. VAR_INPUT

Name	Data Type	Initial Value	Description, parameter values
`IN`	`BOOL`	`FALSE`	Falling edge (`TRUE -> FALSE`): Time delay starts. Rising edge (`FALSE -> TRUE`): Reset of the time delay.
`PT`	`TIME`	`TIME#0ms`	Delay time in milliseconds (ms) (Upper limit for counting up `ET`).

Name

Data Type

Initial Value

Description, parameter values

IN

BOOL

FALSE

Falling edge (TRUE -> FALSE): Time delay starts.

Rising edge (FALSE -> TRUE): Reset of the time delay.

PT

TIME

TIME#0ms

Delay time in milliseconds (ms) (Upper limit for counting up ET).

Table 100. VAR_OUTPUT

Name	Data Type	Initial Value	Description, parameter values
`Q`	`SAFEBOOL`	`FALSE`	Falling edge as soon as `ET` has reached the upper limit of the time delay (`PT`). `FALSE` when `IN = FALSE` and `ET = PT`
`ET`	`TIME`	`TIME#0ms`	Current state of the delay time. Starts counting up as soon as `IN = FALSE` and stops when `ET = PT`.

Name

Data Type

Initial Value

Description, parameter values

Q

SAFEBOOL

FALSE

Falling edge as soon as ET has reached the upper limit of the time delay (PT).

FALSE when IN = FALSE and ET = PT

ET

TIME

TIME#0ms

Current state of the delay time. Starts counting up as soon as IN = FALSE and stops when ET = PT.

Figure 118. Timing diagram: SF_TOF