PLC programming : Siemens STEP 7


This would be useful for Maintenance personal still using old version of Siemens STEP 7

• Installation and authorization
The first time you use STEP 7, install it and transfer the authorization from diskette to the hard disk
• Plan your controller
Before you work with STEP 7, plan your automation solution from dividing the process into individual tasks to creating a configuration diagram Design the program structure
Turn the tasks described in the draft of your controller design into a program structure using the blocks available in STEP 7
• Start STEP 7
You start STEP 7 from the Windows 95/98/NT user interface
• Create a project structure
A project is like a folder in which all data are stored in a hierarchical structure and are available to you at any time. After you have created a project, all other tasks are executed in this project Configure a station
When you configure the station you specify the programmable controller you want to use; for example, SIMATIC 300, SIMATIC 400
• Configure hardware
When you configure the hardware you specify in a configuration table which modules you want to use for your automation solution and which addresses are to be used to access the modules from the user program. The properties of the modules can also be assigned using
• Configure networks and communication connections
The basis for communication is a pre-configured network. For this, you will need to create the subnets required for your automation networks, set the subnet properties, and set the network connection properties and any communication connections required for the networked stations
• Define symbols
You can define local or shared symbols, which have more descriptive names, in a symbol table to use instead of absolute addresses in your user program
• Create the program
Using one of the available programming languages create a program linked to a module or independent of a module and store it as blocks, source files, or charts
• S7 only: generate and evaluate reference data
You can make use of these reference data to make debugging and modifying your user program easier
• Configure messages
You create block-related messages, for example, with their texts and attributes. Using the transfer program you transfer the message configuration data created to the operator interface system database (for example, SIMATIC WinCC, SIMATIC ProTool)
• Configure operator control and monitoring variables
You create operator control and monitoring variables once in STEP 7 and assign them the required attributes. Using the transfer program you transfer the operator control and monitoring variables created to the database of the operator interface system WinCC
• Download programs to the programmable controller
S7 only: after all configuration, parameter assignment, and programming tasks are completed, you can download your entire user program or individual blocks from it to the programmable controller (programmable module for your hardware solution).
• Test programs
S7 only: for testing you can either display the values of variables from your user program or a CPU, assign values to the variables, and create a variable table for the variables that you want to display or modify
• Monitor operation, diagnose hardware
You determine the cause of a module fault by displaying online information about a module. You determine the causes for errors in user program processing with the help of the diagnostic buffer and the stack contents. You can also check whether a user program can run on a particular CPU
• Document the plant
After you have created a project/plant, it makes sense to produce clear documentation of the project data to make further editing of the project and any service activities easier