BECKHOFF EL6900-FB - Manual (Page 38)

Function blocks
36 Function blocks for TwinSAFE logic terminals
ERR_ACK input of the related TwinSAFE group.
Furthermore each time 2 inputs (MonIn1 and MonIn2, MonIn3 and MonIn4 and Secure1 and Secure2)
can be consolidated as input pairs, whereby the signal states of both inputs can only deviate from each
other within a configurable discrepancy time. If this discrepancy time is exceeded for an input pair, the FB
MON will also go into the error state. The characteristics for acknowledging a discrepancy error can be
set via the checkbox ‘Safe Inputs after Disc Error’. If the checkbox is set, both inputs of the input group
that has caused the discrepancy error have to return logical zero simultaneously before the error can be
reset.
The safe state must have been requested at least once on each active MonIn input after starting the FB
MON if the manual function test is active, before an edge of the restart input reacts.