Technical data
Contents
Programming with STEP 7
Manual, 05/2010, A5E02789666-01 21
26 Tips and Tricks........................................................................................................................................551
26.1 Exchanging Modules in the Configuration Table..................................................................551
26.2 Projects with a Large Number of Networked Stations..........................................................551
26.3 Rearranging ..........................................................................................................................552
26.4 Editing Symbols Across Multiple Networks ..........................................................................552
26.5 Testing with the Variable Table ............................................................................................553
26.6 Modifying Variables With the Program Editor.......................................................................554
26.7 Virtual Work Memory ............................................................................................................555
27
Appendix ..................................................................................................................................................557
27.1 Operating Modes ..................................................................................................................557
27.1.1 Operating Modes and Mode Transitions ..............................................................................557
27.1.2 STOP Mode ..........................................................................................................................560
27.1.3 STARTUP Mode ...................................................................................................................561
27.1.4 RUN Mode ............................................................................................................................569
27.1.5 HOLD Mode..........................................................................................................................570
27.2 Memory Areas of S7 CPUs...................................................................................................571
27.2.1 Distribution of the Memory Areas .........................................................................................571
27.2.2 Load Memory and Work Memory .........................................................................................572
27.2.3 System Memory....................................................................................................................574
27.2.3.1 Using the System Memory Areas .........................................................................................574
27.2.3.2 Process-Image Input/Output Tables.....................................................................................576
27.2.3.3 Local Data Stack...................................................................................................................580
27.2.3.4 Interrupt Stack.......................................................................................................................581
27.2.3.5 Block Stack ...........................................................................................................................582
27.2.3.6 Diagnostic Buffer...................................................................................................................583
27.2.3.7 Evaluating the Diagnostic Buffer...........................................................................................583
27.2.3.8 Retentive Memory Areas on S7-300 CPUs..........................................................................585
27.2.3.9 Retentive Memory Areas on S7-400 CPUs..........................................................................586
27.2.3.10 Configurable Memory Objects in the Work Memory.............................................................587
27.3 Data Types and Parameter Types........................................................................................588
27.3.1 Introduction to Data Types and Parameter Types................................................................588
27.3.2 Elementary Data Types ........................................................................................................589
27.3.2.1 Format of the Data Type INT (16-Bit Integers) .....................................................................590
27.3.2.2 Format of the Data Type DINT (32-Bit Integers) ..................................................................590
27.3.2.3 Format of the Data Type REAL (Floating-Point Numbers)...................................................591
27.3.2.4 Format of the Data Types WORD and DWORD in Binary Coded Decimal Numbers..........595
27.3.2.5 Format of the Data Type S5TIME (Time Duration)...............................................................596
27.3.3 Complex Data Types ............................................................................................................597
27.3.3.1 Complex Data Types ............................................................................................................597
27.3.3.2 Format of the Data Type DATE_AND_TIME........................................................................598
27.3.3.3 Using Complex Data Types..................................................................................................600
27.3.3.4 Using Arrays to Access Data ................................................................................................601
27.3.3.5 Using Structures to Access Data..........................................................................................604
27.3.3.6 Using User-Defined Data Types to Access Data..................................................................606