Response To Nck Failure - Siemens SINUMERIK 840D sl Function Manual

13.10.6

Response to NCK failure

General
During cyclic operation, the PLC basic program continuously monitors NCK availability by
polling the signoflife character. If the NCK is no longer reacting, the NCK PLC interface is
initialized, and the NCK CPU ready signal in the area of the signals from NC (DB 10.DBX
104.7) is reset. Furthermore, the signals sent from the NCK to the PLC and vice versa are set
to an initial state.
The PLC itself remains active so that it can continue to control machine functions. However,
it remains the responsibility of the user program to set the machine to a safe state.
NCK → PLC signals
The signals sent by the NCK to the PLC are divided into the following groups:
● Status signals from the NCK, channels, axes and spindles
● Modification signals of the auxiliary functions
● Values of the auxiliary functions
● Values of the G functions
Status signals:
The status signals from the NCK, channels, axes, and spindles are reset.
Auxiliary-function modification signals:
Auxiliary-function modification signals are also reset.
Auxiliary-function values:
Auxiliary-function values are retained so that it is possible to trace the last functions triggered
by the NCK.
G-function values:
G function values are reset (i.e. initialized with the value 0 respectively).
PLC → NCK signals
The signals sent by the PLC to the NCK are divided into control signals and tasks that are
transferred by FCs to the NCK.
Control signals:
The control signals from the PLC to the NCK are frozen; cyclic updating by the basic program
is suspended.
Jobs from PLC to NCK:
The FCs and FBs, which are used to pass jobs to the NCK, must no longer be processed by
the PLC user program, as this could lead to incorrect checkback signals. During powerup of
the control, a job (e.g. read NCK data) must not be activated in the user program until the NCK
CPU ready signal is set.
Basic Functions
Function Manual, 01/2015, 6FC5397-0BP40-5BA2
P3: Basic PLC program for SINUMERIK 840D sl
13.10 Structure and functions of the basic program
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