Siemens SINUMERIK 840Di Function Manual page 955

2.7 Structure and functions of the basic program
2.7
General
The program is modular in design, i.e., it is structured according to NCK functions.
In the operating system, a distinction is made between the following levels of execution:
• Startup and synchronization (OB 100)
• Cyclic mode (OB 1)
• Process interrupt handling (OB 40)
Each section of the basic program - as illustrated in the figure below - must be called by the
user in OBs 1, 40 and 100.
Power Line Basic PLC Program (P3)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0
2.7 Structure and functions of the basic program
Detailed description
2-43