Siemens NAN 67 Series Wartungshandbuch PDF herunterladen (Seite 31)

3-7

Ladder Logic (LAD) for S7-300 and S7-400

C79000-G7076-C504-02

The columns in the variable declaration table are interpreted as follows:

Table 3-2 Columns of the Variable Declaration Table

Column Meaning Remarks Editing

Address Address in format BYTE.BIT In the case of data types which require more

than one byte, the address indicates this with

a jump to the next byte address.

Key:

* : Size of an array element in bytes

+ : Initial address, ref. to the structure start

= : Total memory requirement of a structure

System entry:

the address is

assigned and

displayed by

the system after

you have

finished

entering your

declaration.

Decl. Declaration type “Purpose” of the

variables

The following are possible depending on

block type:

Input parameters “in”

Output parameters “out”

In/out parameters “in_out”

Static variables “stat”

Temporary variables “temp”

Default settings

according to

block type

Symbol Symbolic name of variables The name must begin with a letter. Reserved

keywords are not permitted.

Mandatory

Data Type Data type of the variable

(BOOL, INT, WORD, ARRAY

etc.)

Basic data types can be selected in the menu

with the right mouse button.

Mandatory

Initial Value Initial value, when the software

should not assume a default value

Must be compatible with the data type.

Unless a specific actual value has been

selected, the initial value is used as the

actual value of the variable when editing a

DB for the first time.

Optional

Comment Comment on documentation Optional

If you have assigned system attributes to a variable, a symbol resembling a

golf flag appears in the “Symbol” column (see Figure 3-3). Double-click the

flag to open the “System Attributes” dialog box.

You can vary the width of the columns. Position the mouse pointer between

two columns and holding the left mouse button pressed move the mouse

horizontally. As an alternative, you can alter the width of the column using

the menu command View

Column Width... having previously selected the

table. This allows you to minimize the optional comment and initial value

columns and focus solely on the remaining columns.

Meaning of the

Columns

Meaning of the

“Golf Flag”

Altering the

Column Width

Creating Logic Blocks

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