SF_Equivalent

This is the web edition of the original ‎⮫ AC500-S safety user manual, version 1.3.2. This web edition is provided for quick reference only. The original safety user manual must be used to meet functional safety application requirements.

Standards	Requirements
ISO 13849-1:2015	6.2.6 Category 3 6.2.7 Category 4 Appendix E.1

Standards

Requirements

ISO 13849-1:2015

6.2.6 Category 3

6.2.7 Category 4

Appendix E.1

This function block converts two equivalent BOOL inputs (both NO or NC) to one BOOL output, including 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.

Table 1029: FB name: SF_Equivalent
Name	Data type	Initial value	Description, parameter values
VAR_INPUT
Activate	BOOL	FALSE	⮫ Table 1021 “General input parameters”
S_ChannelA	BOOL	FALSE	Variable. Input A for logical connection. FALSE: Contact A open. TRUE: Contact A closed.
S_ChannelB	BOOL	FALSE	Variable. Input B for logical connection. FALSE: Contact B open. TRUE: Contact B closed.
DiscrepancyTime	TIME	T#0ms	Constant. Maximum monitoring time for discrepancy status of both inputs.
VAR_OUTPUT
Ready	BOOL	FALSE	⮫ Table 1022 “General output parameters”
S_EquivalentOut	BOOL	FALSE	Safety related output. FALSE: Minimum of one input signal = "FALSE" or status change outside of monitoring time. TRUE: Both input signals "active" and status change within monitoring time.
SafetyDemand	BOOL	FALSE	Optional. ⮫ Table 1022 “General output parameters”
Error	BOOL	FALSE	⮫ Table 1022 “General output parameters”
DiagCode	WORD	16#0000	⮫ Table 1022 “General output parameters”

Typical timing diagrams

SF_Equivalent_TimingDiagram_1 — Fig. 521: Typical timing diagram for SF_Equivalent

SF_Equivalent_TimingDiagram_2 — Fig. 522: Typical timing diagram for SF_Equivalent with exceeding the DiscrepancyTime

Error detection

The function block monitors the discrepancy time between channel A and B, when switching to TRUE and also when switching to FALSE.

Error behavior

S_EquivalentOut is set to FALSE. Error is set to TRUE. DiagCode indicates the error states. There is no reset defined as an input coupled with the reset of an error. If an error occurs in the inputs, a new set of inputs with correct S_EquivalentOut must be able to reset the error flag. (Example: If a switch is faulty and replaced, using the switch again results in a correct output.)

Function block-specific error and status codes

Table 1030: FB-specific error codes
DiagCode	State name	State description and output setting
C010	Error 1	Discrepancy time elapsed in state 8802. Ready = TRUE S_EquivalentOut = FALSE SafetyDemand = FALSE Error = TRUE
C020	Error 2	Discrepancy time elapsed in state 8804. Ready = TRUE S_EquivalentOut = FALSE SafetyDemand = FALSE Error = TRUE
C030	Error 3	Discrepancy time elapsed in state 8806. Ready = TRUE S_EquivalentOut = FALSE SafetyDemand = FALSE Error = TRUE

Table 1031: FB-specific status codes (no error):
DiagCode	State name	State description and output setting
0000	Idle	The function block is not active (initial state). Ready = FALSE S_EquivalentOut = FALSE SafetyDemand = FALSE Error = FALSE
8801	Init	An activation has been detected by the FB and the FB is now activated. Ready = TRUE S_EquivalentOut = FALSE SafetyDemand = TRUE Error = FALSE
8000	Safety Output Enabled	The inputs switched to TRUE in equivalent mode. Ready = TRUE S_EquivalentOut = TRUE SafetyDemand = FALSE Error = FALSE
8802	Wait for Channel B	Channel A has been switched to TRUE - waiting for channel B; discrepancy timer started. Ready = TRUE S_EquivalentOut = FALSE SafetyDemand = TRUE Error = FALSE
8804	Wait for Channel A	Channel B has been switched to TRUE - waiting for channel A; discrepancy timer started. Ready = TRUE S_EquivalentOut = FALSE SafetyDemand = TRUE Error = FALSE
8806	From Active Wait	One channel has been switched to FALSE; waiting for the second channel to be switched to FALSE, discrepancy timer started. Ready = TRUE S_EquivalentOut = FALSE SafetyDemand = TRUE Error = FALSE