Acknowledging Faults - Siemens Simatic Manual

Fail-safe function blocks for storage and retrieval machines
21. In order to permit retraction, X_POSITIVE_OK or X_NEGATIVE_OK is reset to 1 with a rising
edge at RELEASE; using a suitable user interconnection, a drive stop response should then
be deselected.
22. If, during retraction, SAFE_V exceeds the value of VMAX_RELEASE or the permitted velocity
of the opposite end zone, assuming this lies under VMAX_RELEASE, then SLS_OK changes
to 0 and DIAG bit 2 is set.
23. A velocity error can always be acknowledged if the actual velocity SAFE_V again lies below
SLS_THRESHOLD.
24. As soon as SAFE_POS has returned to the parameterized, permitted range, after acknowl-
edgment, the axis can again travel at the full velocity; this means that the permitted velocity of
the envelope curve monitoring is output and monitored at SLS_THRESHOLD.
ERROR and DIAG change back to 0.
25. If V_VALID = 0 while SAFE_POS is outside the parameterized travel range, then the retrac-
tion velocity can no longer be monitored in a safety-related fashion. Therefore, selection using
RELEASE = 1 has no effect.
26. To continue retraction, a 1 signal must again be set at block F_SAFE_POS by acknowledging
V_VALID.
27. Retraction can then be continued. Alternatively, a jump can be made back to the initial state
by deselecting RELEASE with subsequent acknowledgment. If SAFE_POS is still outside the
parameterized travel range, then the response corresponds to Point 17.
Safety notes and instructions
The parameterization of input V_MAX_RELEASE must be adapted to the permis-
sible safely reduced velocity according to the application-specific risk assess-
ment.
Warning
The interconnection of output MOVE_POSITIVE_OK must match the selection of
the SDI drive function for the positive direction. For MOVE_POSITIVE_OK = 0,
motion must no longer be possible in the positive direction.
The same applies when interconnecting the MOVE_NEGATIVE_OK output – and
inhibiting the negative direction of motion.
It is absolutely essential that the block outputs are connected with the correct
signals for controlling the drive.
Otherwise, an impermissible motion toward the end stops is possible, which can-
not be identified internally by the block.
3.6.3.4

Acknowledging faults

28. DIAG and ERROR are reset to 0 with a positive edge at ACK, assuming that no other fault is
active. The block immediately indicates that it can be acknowledged with a 1 signal at its out-
put ACK_REQ. ACK_REQ is reset to 0 after a positive edge at ACK.
S7-Distributed Safety/SIMATIC Safety - fail-safe function blocks for storage and retrieval machines
- 3-37 -