Loss of voltage
Siemens AG, 2003. All rights reserved
SINUMERIK 840Di Manual (HBI) – 06.03 Edition
The NC will signal the detected fatal exceptional error to the PLC by means
of the interface signal "PC OS fault".
Depending on the current machining situation, the PLC user program can either
continue the machining or end it.
After completion of the machining, the PLC user program can request a shut-
down of the PC by sending the interface signal "PC shutdown" to the NC.
Due to the interface signal "PC shutdown":
– the retentive NC and PLC data are stored
– NC and PLC ended.
For a brief description of the interface signals "PC OS fault" and "PC shut-
down", please refer to Subsection 16.1.1, Page 16-499.
The further sequence is as defined in the Windows NT configuration (settable in
the System Properties, tab: Start/shutdown):
– Stop (Blue Screen) (default)
– Automatic restart (reboot).
The interface signal "PC shutdown" must be reset in the organization block
OB100 (cold restart) of the PLC.
A loss of voltage lasting more than five msecs is detected by the POWER FAIL
functionality of the SINUMERIK 840Di as a fault scenario and the following ac-
tions are initiated:
– The background lighting of the operator panel display is switched off
– The NC and PLC are shut down correctly
– The NC and PLC user data are saved in the SRAM of the MCI board.
With the next power-up of the SINUMERIK 840Di, the battery-backed user data
are available again. The SINUMERIK 840Di is thus immediately ready again
without data loss.
If the power supply is recovered before final shutdown of the PCU, the following
message box will be displayed:
SINUMERIK 840Di NCK/PLC
Alarm: Power-Fail detected, NCK/PLC restart with OK.
1 General on the SINUMERIK 840Di
1.1 Overview of SINUMERIK 840Di