How to configure Racks in SIEMENS PLC

Configuration Table as a Representation of a Rack

For a local configuration you arrange the modules beside the CPU in a rack and continue into

additional expansion racks. The number of racks which can be configured depends on the CPU

you used.

Just as you do in a real plant, you arrange your modules in racks with STEP 7. The difference is

that in STEP 7 racks are represented by "configuration tables" that have as many rows as the rack

has slots for modules.

The following figure shows an example of how a real structure is converted into a configuration

table. The configuration table corresponds to the rack used; STEP 7 automatically places the

number of the rack in brackets in front of the name.

Example: (0) UR corresponds to the central rack (Universal Rack) number 0.

Opening Objects in HW Config

In STEP 7, you can open objects in order to edit them.

In the SIMATIC Manager, for example, select the "Hardware" object and then select the menu

command Edit > Open Object to start HW Config. You can edit the station configuration with HW

Config.

Double-clicking on the object has the same effect as "Edit Objects".

Special Feature of HW Config

If want to edit an object in HW Config, the double-clicking it produces the same result as selecting

the menu command Edit > Object Properties. In general, this is the place to assign addresses,

set parameters or enter other information. If there is an application available to edit the object, then

a button for starting this application is located in the property sheet for the object.

As of STEP 7 V5.4, the menu command Edit > Open Object With is available. You can use this

menu command to open an application to edit the object as required. This menu command is only

available if such an application is necessary and available for use.

Setting the Properties of Components

Once you have arranged your components in the station window, you always arrive in the following

manner in a dialog box for changing the default properties (parameters or addresses):

• Double-click the component or select the menu command Edit > Object Properties.

• Right mouse button: Move the cursor on the component, press the right mouse button and

select the command Object Properties from the pop-up menu.

Properties of CPUs

The properties of the CPUs have a special significance for the behavior of the system. In the dialog

boxes for a CPU, you can set the following, for example: startup characteristics, local data areas

and priorities for interrupts, memory areas, retentive behavior, clock memory, protection level, and

password - to name only a few. STEP 7 "knows" what can be set and within what range limits.

In the "General" tab of the CPU or via the properties of the CPU interface you can assign

parameters to the interfaces (for example, MPI or integrated PROFIBUS-DP interfaces). Via these

dialog boxes you can also access the properties dialog box for the corresponding subnet to which

the CPU is to be connected.

Other Ways of Assigning Parameters

For S7-300 and S7-400 programmable controllers you can set the parameters for some modules in

the user program (for example, for analog modules). You need to call the system functions (SFCs)

WR_PARM, WR_DPARM, and PARM_MOD in the user program to do this. These settings are lost

following a warm restart.

You will find more detailed information about system functions in the System Software for S7-300

and S7-400, System and Standard Functions Reference Manual

What You Should Know About Slot Rules and Other Rules

STEP 7 offers you support with configuring a station so that a message is generally displayed

immediately if, for example, a module cannot be inserted in the slot you want to insert it in.

As of STEP 7 V5.2 you can identify available module slots at a glance, provided you have your

monitor display set for more than 256 colors. When you select a module in the Hardware Catalog

and this module can be inserted in a configured module rack, all slots available for the insertion of

this module are highlighted in color. This feature increases configuring efficiency.

Furthermore, because address ranges are checked automatically, double address assignments

cannot occur.

In this connection, please pay attention to the status bar at the lower edge of the window and to

any displayed messages that provide details on the causes and effects of an operation. You can

also use the online help to obtain additional information for the messages.

Other additional, temporary rules (for a specific release), such as restrictions to the slots you can

use owing to a functional restriction to individual modules, are not taken into account.

Consequently, always consult the documentation or the current Product Information for the

modules.