Siemens SINUMERIK 840D Description Of Functions page 140

3 Safety-Related Functions
3.10 Safe programable logic (SPL) (840D SW 4.4.18)
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Protective
mechanisms
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•
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If NCK-SPL execution is interrupted for any reason or the SI system variables
are changed by another program, then this is detected by the cyclic crosswise
data comparison with the PLC.
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SINUMERIK 840D/SIMODRIVE 611 digital SINUMERIK Safety Integrated (FBSI) - Edition 11.03
− In order to check the program the status of the active synchronous
actions (operating area "Machine", soft key "Synchronous actions") can
be displayed.
− The program can be modified during commissioning. It must then be re-
started.
− The NCK-SPL program is stored in the NCK path _N_CST_DIR as
subroutine "_N_SAFE_SPF" (MMC view: standard cycles/SAFE.SPF).
Other sub-routine names are not permitted.
− The NCK-SPL program must be started after commissioning.
− The images of the PLC safety variables ($A_INSIP(D), $A_OUTSIP(D),
$A_INSEP(D), $A_OUTSEP(D), $A_MARKERSIP(D) ) are required for
the simulation (NC side) of an SPL. These can be used to develop the
SPL step-by-step. They can only be read by the NCK.
The synchronous action IDs used for the NCK-SPL are protected from
being influenced by the PLC or other programs using
MD $MN_PREVENT_SYNACT_LOCK. It is then no longer possible to
change these synchronous actions (CANCEL, LOCK have no effect) once
_N_SAFE_SPF has been started.
The system variables $A_OUTSI, $A_OUTSID, $A_OUTSE, $A_OUTSED,
$A_MARKERSI, $A_TIMERSI and $A_CMDSI are protected from being
written to by programs other than the (/_N_CST_DIR/_N_SAFE_SPF). If
an error occurs Alarm 17070 "Channel %1 block %2 data item write-
protected" is output.
A reference checksum is calculated at run-up by the NCK-SPL
(/_N_CST_DIR/_N_SAFE_SPF) that is entered into the program as a
comment:
Example: ; SAFE_CHECKSUM = 000476bbH
The checksum is then cyclically re-calculated and compared with the
reference checksum. If a deviation is detected, Alarm 27093 "Checksum
error NCK-SPL, %1, %2, %3" is output.
The system variables $A_INSIP(D), $A_OUTSIP(D), $A_INSEP(D),
$A_OUTSEP(D) and $A_MARKERSIP(D) are only accessible during the
commissioning phase.
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11.03