System Constants - Siemens S7-1200 Programming Manualline

2 S7-1200/1500 Innovations

2.11 System constants

Example
Filling level:= Radius * Radius * PI * height;
// calculation of the filling level for medium tank
2.11 System constants
For S7-300/400 controllers the identification of hardware and software components
is performed by logic address or diagnostic addresses.
For S7-1200/1500 the identification is by system constants. All hardware and
software components (e.g. interfaces, modules, OBs, ...) of the S7-1200/1500
controllers have their own system constants. The system constants are
automatically created during the setup of the device configuration for the central
and distributed I/O.
Advantages
You can address via module names instead of hardware identification.
Recommendation
Assign function-related module names in order to identify the modules easily
during programming.
Example
In the following example you can see how system constants are used in the user
program.
Figure 2-15: "System constants" in the user program
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Programming Guideline for S7-1200/1500
V1.2, Entry ID: 81318674
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