Siemens SINUMERIK 840D sl Programming Manual page 168

Flexible NC programming
1.25 Subprogram technique
Division of program levels:
● Program level 0: Main program level
● Program level 1 to 15: Subprogram level 1 to 15
Interrupt routines (ASUB)
If a subprogram is called in the context of an interrupt routine, this will not be executed at the
program level currently active in the channel (n) but at the next lowest program level (n+1).
So that this remains possible even at the lowest program level, 2 additional program levels
(16 and 17) are available in conjunction with interrupt routines.
If more than 2 program levels are required, this has to be taken into account explicitly in the
structuring of the part program executed in the channel. In other words, only a maximum of
as many program levels may be used in order to leave sufficient program levels available for
interrupt processing.
If interrupt processing needs 4 program levels for example, the part program must be
structured so that it uses a maximum of up to program level 13. In the event of an interrupt,
the 4 program levels it requires (14 to 17) will be available to it.
Siemens cycles
Siemens cycles need 3 program levels. Therefore, a Siemens cycle must be called at the
latest in:
● Part program processing: program level 12
● interrupt routine: program level 14
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Programming Manual, 06/2009, 6FC5398-2BP20-0BA0
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