Siemens NAN 67 Series Manual de servicio descargar pdf (Pagina 30)

3-6

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

C79000-G7076-C504-02

3.3 Structure of the Variable Declaration Table

In the variable declaration table, you set the local variables including the

formal parameters of the block and the system attributes for parameters. This

has (among other things) the following effects:

S As a result of the declaration, memory is reserved in the local data stack

or instance data block.

S By setting the input, output, and in/out parameters you also define the

“interface” for calling a block in the program.

S Declaring variables in a function block provides the data structure for any

instance data block that you associate with the function block.

S By setting system attributes, you assign special properties to parameters

for message and connection configuration, operator interface functions

and process control configuration.

After opening a new logic block, a default variable declaration table is

displayed on the screen. This lists all the permitted declaration types for the

specific block (in, out, in_out, stat, temp) in the appropriate order.

When creating a new OB, a standard variable declaration is displayed in

which you can change the values.

The variable declaration table contains entries for the address, declaration,

symbolic name, data type, initial value, and comment for the variables. Each

table row represents a variable declaration. Variables of the data type array or

structure require more than one row.

TRAFFIC\...\FB40 - <Offline>

Address Decl. Symbol Data Type Initial Value Comment

ein

start

Motor

in_outp1

BOOL

INT

FALSE

out

in_out

0.0

0.1

2.0

2.1

4.0

Message BOOL

in_outp2 INTin_out6.0 0

FALSE

Light on

Switch

Motor

Figure 3-3 Example of a Variable Declaration Table

Overview

Structure of the

Variable

Declaration Table

Creating Logic Blocks

1 2 ... 25 26 27 28 29 30 31 32 33 34 35 ... 317 318

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