SF_Antivalent (FB)

FUNCTION_BLOCK SF_Antivalent

This function block converts two antivalent SAFEBOOL inputs (NO/NC pair) to one SAFEBOOL output with discrepancy time monitoring.

This FB should not be used stand-alone since it has no restart interlock. It is required to connect the output to other safety related functionalities.

Function block according to PLCopen, Technical Committee 5: Safety Software (Technical Specification), Part 1: Concepts and Function Blocks, Version 2.01 (2020-2)

InOut:

Scope	Name	Type	Initial	Comment
Input	Activate	BOOL	FALSE	Activation of the FB.
	S_ChannelNC	BOOL	FALSE	Input for NC (Normally Closed) connection. FALSE: NC contact open, TRUE: NC contact closed.
	S_ChannelNO	BOOL	FALSE	Input for NO (Normally Open) connection. FALSE: NO contact open, TRUE: NO contact closed.
	DiscrepancyTime	TIME	TIME#0ms	Maximum monitoring time for discrepancy status of both inputs
Output	Ready	BOOL	FALSE	Activation of the FB. TRUE indicates that the FB is activated and the outputs results are valid, FALSE the FB is not active and the program is not executed.
	S_AntivalentOut	BOOL	FALSE	Safety related output
	SafetyDemand	BOOL	FALSE	Output indicating that the FB is active and the primary safety function is demanded (e.g. related to the safety functionality).
	Error	BOOL	FALSE	Error flag
	DiagCode	WORD	0	Diagnostic register