Siemens Simatic S7 Series System Manual

Table of contents
S7-200 SMART
6 System Manual, 09/2015, A5E03822230-AC
4 PLC concepts .......................................................................................................................................... 55
4.1 Execution of the control logic ................................................................................................. 55
4.1.1 Reading the inputs and writing to the outputs ........................................................................ 57
4.1.2 Immediately reading or writing the I/O ................................................................................... 57
4.1.3 Executing the user program ................................................................................................... 58
4.2 Accessing data ....................................................................................................................... 60
4.2.1 Accessing memory areas ....................................................................................................... 61
4.2.2 Format for Real numbers ....................................................................................................... 68
4.2.3 Format for strings ................................................................................................................... 68
4.2.4 Assigning a constant value for instructions ............................................................................ 69
4.2.5 Addressing the local and expansion I/O ................................................................................ 69
4.2.6 Using pointers for indirect addressing ................................................................................... 70
4.2.7 Pointer examples ................................................................................................................... 73
4.3 Saving and restoring data ...................................................................................................... 75
4.3.1 Downloading project components .......................................................................................... 75
4.3.2 Uploading project components .............................................................................................. 77
4.3.3 Types of storage .................................................................................................................... 78
4.3.4 Using a memory card ............................................................................................................. 79
4.3.5 Inserting a memory card in the CPU ...................................................................................... 81
4.3.6 Transferring your program with a memory card ..................................................................... 81
4.3.7 Restoring data after power on ................................................................................................ 84
4.4 Changing the operating mode of the CPU ............................................................................. 84
5 Programming concepts ............................................................................................................................ 85
5.1 Guidelines for designing a PLC system ................................................................................. 85
5.2 Elements of the user program ................................................................................................ 87
5.3 Creating your user program ................................................................................................... 90
5.3.1 Earlier versions of STEP 7-Micro/WIN projects ..................................................................... 90
5.3.2 Using STEP 7-Micro/WIN SMART user interface .................................................................. 92
5.3.3 Using STEP 7-Micro/WIN SMART to create your programs ................................................. 93
5.3.4 Using wizards to help you create your control program......................................................... 94
5.3.5 Features of the LAD editor ..................................................................................................... 95
5.3.6 Features of the FBD editor ..................................................................................................... 96
5.3.7 Features of the STL editor ..................................................................................................... 96
5.4 Data block (DB) editor ............................................................................................................ 97
5.5 Symbol table ........................................................................................................................ 100
5.6 Variable table ....................................................................................................................... 104
5.7 PLC error reaction ................................................................................................................ 109
5.7.1 Non-fatal errors and I/O errors ............................................................................................. 110
5.7.2 Fatal errors ........................................................................................................................... 111
5.8 Program edit in RUN mode .................................................................................................. 112
5.9 Features for debugging your program ................................................................................. 114

Siemens Simatic S7 Series Specifications

General

CPU	Varies by model (e.g., S7-300, S7-400, S7-1200, S7-1500)
Communication Interfaces	PROFIBUS, PROFINET, Ethernet, MPI
Programming	TIA Portal, STEP 7
Programming Languages	LAD, FBD, STL, SCL, GRAPH
I/O Modules	Digital, Analog, Specialty modules available
Operating Temperature	0°C to 60°C (standard models)
Mounting	DIN rail mounting
Operating Voltage	24V DC or 120/230V AC (varies by model)
Protection Class	IP20 (standard models)
Memory	Varies depending on the S7 model. Includes work memory (RAM) for program execution, load memory (EEPROM or Flash) for program storage, and system memory for operating system functions. Memory sizes range from kilobytes to megabytes.