4 Software 02.2001
© Siemens AG 2001 All Rights Reserved
4
-32 SINUMERIK 840Di System Overview (SYI) - 02.2001 Edition
4.1 Windows NT
The operating system basis of the SINUMERIK 840Di is Windows NT 4.0 (US ver-
sion). Since, however, it is well known that Windows NT is only conditionally real-
time capable (the term 'smooth real time' is used in this context), Siemens has de-
veloped a method enabling the NC system software to be operated under hard real
time conditions, without modifying Windows NT.
Computation time distribution
Windows NT and the NCK (Numerical Control Kernel), which is part of the system
software and realizes the real time capability of the SINUMERIK 840Di, share the
available PCU processor performance provided by the SINUMERIK 840Di at a de-
fined ratio.
By default, 65% of the computation time are assigned to the NCK. This value,
however, is the maximum value claimed by the NCK in the worst case only. If the
NCK requires less computation time, it will give this dynamically to Windows NT.
Fatal exception (blue screen)
If Windows NT detects a fatal exception during the operation of the NC system
software, the following steps are carried out:
- The execution of Windows NT will stop.
- An error message appears on the screen.
- NC and PLC continue to operate as normal.
- The NC reports the detected fatal exception to the PLC.
Depending on the current machining situation, the PLC user program or the op-
erator can decide locally whether the machining is continued without any negative
effects or whether it is terminated.
4.2 NC software
It is well known that the SINUMERIK 840Di possesses a very powerful NC soft-
ware. With the exception of some special hardware and drive-specific functions, as
well as a few options, the NC functionality corresponds to that of the SINUMERIK
840D.
The following functions will be mentioned as examples for the fields machining or-
ganization and motion control:
• Flexible channel structure for parallel execution of part programs
• Summary of channels in mode groups
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