Siemens CPU 948 - Page 81

Nesting depth You can only nest 40 blocks within one another. If more than 40
blocks are called, the CPU signals an error and goes to the stop mode.
Example of nesting depth
You can determine the nesting depth of your program as follows:
- Add all the organization blocks you have programmed
(in the example: 4 OBs).
- Add the nesting depth of the individual organization blocks
(in the example: 2 + 2 + 1 + 0 = 5).
- Add the two amounts together to obtain the program nesting depth
(in the example: 4 + 5 = nesting depth 9). It must not exceed a value
of 40.
OB 25
Nesting depth
1
2
3
4
5
6
7
89
OB 1
PB 1
FB 1
OB 13
PB 131 FB 131
OB 2
FB 21
Program
processing
level
Fig. 3-5 Example of block nesting depth
Program Organization
CPU 948 Programming Guide
C79000-G8576-C848-04
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