Program Blocks - Siemens SIMATIC S5-100U System Manual

S5-100U
7.3.2

Program Blocks

Self-contained program parts are programmed in program blocks (PB).
Special feature: Control functions can be represented graphically in program blocks.
Call
Block calls JU and JC activate program blocks. You can program these operations in all block types
except data blocks. Block call and block end cause the RLO to be reloaded. However, the RLO
can be included in the "new" block and be evaluated there.
7.3.3 Sequence Blocks, for CPU 103 and Higher
Sequence blocks (SB) are special program blocks that process sequence controls. They are treated
like program blocks.
7.3.4 Function Blocks
Frequently recurring or complex control functions are programmed in function blocks (FB).
Function blocks have the following special features.
• FBs can be assigned parameters (for CPU 103 and higher).
- Actual parameters can be assigned when the block is called (for CPU 103 and higher).
• FBs have an extended set of operations not available to other blocks.
• The FB program can be written and documented in STL only.
If you are using CPU 102 version 8MA02 or higher, you have the following types of function blocks
available:
• FBs that you can program
• FBs that are integrated in the operating system (see section 9.2)
• FBs that are available as software packages (standard function blocks, see Catalog ST 57)
EWA 4NEB 812 6120-02b
Introduction to STEP 5
7-11