SF_ResetButton

Applicable Safety Standards

SF_ResetButton is a certified PLCopen function block. For detailed information about the applied standards , see: "PLCopen – Technical Committee 5 – Safety Software"

Important

The requirements which are listed in the standards must be met by the user.

Interface Description

This function block adds the trailing edge functionality to all the function blocks with reset input with rising edge detection. This can be used to comply with EN ISO 13849-1:2015.

Table 25. VAR_INPUT

Name	Data Type	Initial Value	Description, Parameter Values
`ResetRequested`	`BOOL`	`TRUE`	Input which should be connected to the `ResetRequest` output of the paired FB `TRUE`: Reset requested `FALSE`: No reset requested / no monitoring of `ResetIn`
`ResetIn`	`BOOL`	`FALSE`	Variable Input of reset button `FALSE`: Reset button released `TRUE`: Reset button actuated by operator.
`TrailingMinimum`	`TIME`	`T#350ms`	Constant; Valid in trailing mode Minimum time that the reset switch has to be actuated. If the reset button is pushed shorter than this time, the reset is ignored. Typical value: 350 ms Absolute minimum value: 100 ms Minimum value: 2 PLC cycles
`TrailingMaximum`	`TIME`	`T#2s`	Constant; Valid in trailing mode Maximum time that the reset switch can be actuated. If the reset button is pushed longer than this time, the reset is ignored. Typical value: 2 s

Important

The ResetOut output is a rising edge (R_TRIG) pulse of length of one FB cycle, which can be connected to any FB which has a reset input, and as such is compliant to the PLCopen Safety FBs version 1.0.

The ResetRequested input is connected to the ResetRequest output of the relevant FB. With this the timing interval is controlled during which the Reset Button needs to be checked.

This FB uses S_AutoReset.

Table 26. VAR_OUTPUT

Name	Data Type	Initial Value	Description, Parameter Values
`Ready`	`BOOL`	`FALSE`	See General Output Parameters
`ResetOut`	`BOOL`	`FALSE`	Pulse for the initiation of the reset procedure This pulse is generated after the falling edge. Pulse output with rising edge first. At least 1 cycle
`Error`	`BOOL`	`FALSE`	See General Output Parameters
`DiagCode`	`WORD`	`16#0000`	See Diagnostic Codes

Figure 26. Function block: SF_ResetButton

Functional Description

For the functional description, see ISO 13849-1:2015, Section 5.6 "Reset Behavior".

Table 27. Logic table of inputs/outputs

Inputs				Outputs
`ResetRequested`	`ResetIn`	`TrailingMinimum`	`TrailingMaximum`	`Ready`	`ResetOut`	`Error`	`DiagCode`
`FALSE`	---	---	---	`FALSE`	`FALSE`	`FALSE`	`16#0000`
`TRUE`	`FALSE`	> = 100 ms	`TrailingMaximum>=TrailingMinimum`	`TRUE`	`FALSE`	`FALSE`	`16#83E2`
`TRUE`	`FALSE` -> `TRUE`	Watchdog is started		`TRUE`	`FALSE`	`FALSE`	`16#83F2`
`TRUE`	`TRUE`	`TrailingMinimum` < elapsed time < `TrailingMaximum`		`TRUE`	`FALSE`	`FALSE`	`16#83F2`
`TRUE`	`TRUE` -> `FALSE`	`TrailingMinimum` < elapsed time < `TrailingMaximum`		`TRUE`	`TRUE`	`FALSE`	`16#8000`
With the next call, there is an automatic transition from `16#8000` to `16#83E2`.							`16#83E2`

Tip

In the logic table, an arrow -> stands for a transition. TRUE -> FALSE means that the value of the variable has changed from TRUE to FALSE.

State diagram

Figure 27. State diagram: SF_ResetButton

Tip

Note: The transition from any state to the Idle state due to Activate = FALSE is not shown. However these transitions have the highest priority.

Typical Timing Diagrams

Figure 28. Timing diagram for SF_ResetButton

Error Detection

If the input ResetIn = TRUE when ResetRequested = TRUE, an error is generated.

If the input ResetRequested = TRUE and ResetIn = TRUE and the time input TrailingMinimum is not reached or the input TrailingMaximum is exceeded, an error is detected.

Error Behavior

In case of a static TRUE signal at the ResetIn input, the DiagCode output indicates the relevant error code and the Error output is set to TRUE.

FB-Specific Error and State Codes

Table 28. FB-specific error codes

`DiagCode`	State Name	State Description and Output Setting
`16#C000`	`Parameter Error`	`TrailingMinimum > TrailingMaximum` OR `TrailingMinimum < 100 ms` `Ready = TRUE` `ResetOut = FALSE` `Error = TRUE`
`16#C001`	`Reset Error`	`ResetIn = TRUE` while waiting for `NOT ResetIn` `Ready = TRUE` `ResetOut = FALSE` `Error = TRUE`
`16#C3E0`	`Error Trailing Maximum`	`TrailingMaximum` elapsed before detecting `F_TRIG` at `ResetIn`. Waiting for `R_TRIG` at `ResetIn` `Ready = TRUE` `ResetOut = FALSE` `Error = TRUE`
`16#C3F0`	`Error Trailing Minimum`	`F_TRIG` at `ResetIn` detected before `TrailingMinimum` has elapsed. Waiting for `R_TRIG` at `ResetIn`. `Ready = TRUE` `ResetOut = FALSE` `Error = TRUE`

Table 29. FB-specific state codes

`DiagCode`	State Name	State Description and Output Setting
`16#0000`	`Idle`	The function block is not active (initial state) `Ready = FALSE` `ResetOut = FALSE` `Error = FALSE`
`16#83E2`	`Wait for R_TRIG`	The function block is enabled. Waiting for `R_TRIG` at `ResetIn` `Ready = TRUE` `ResetOut = FALSE` `Error = FALSE`
`16#83F2`	`Wait for F_TRI`	`ResetIn = TRUE`. Waiting for `F_TRIG` at `ResetIn` `Ready = TRUE` `ResetOut = FALSE` `Error = FALSE`
`16#8000`	`Reset Detected`	Valid reset behavior was detected. The state is valid for at least one cycle and will automatically transfer to `83E2`. `Ready = TRUE` `ResetOut = TRUE` `Error = FALSE`