Siemens NAN 67 Series Manual de Serviço descarregar pdf (Página 23)

2-7

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

C79000-G7076-C504-02

2.3 Rules to Observe

The order in which you create logic blocks and data blocks in a user program

is important. As a rule: if blocks are called within other blocks, the called

blocks must already exist before you program their calls. Entering a

non-existent block as a Ladder element (box) is not possible. If you program

a call for a non-existent block using CALL, an error is reported when you

save the program because the called block cannot be found.

With STEP 7 you can edit a user program stored on the CPU online while the

CPU is in the RUN mode.

Warning

If you make online modifications to a program while it is running, this can

lead to malfunctions and unforeseen reactions in your plant or process that

could cause injury to persons or damage to equipment.

If the CPU is switched online and is in the RUN mode, modifying the user

program stored on the CPU can cause situations in which machines and

devices are suddenly turned on or off, potentially causing injury to persons

or damage to equipment.

Always plan the sequence of events in your process in accordance with the

pertinent safety regulations. Never attempt to make online modifications to a

program while it is running without having first considered the consequences

and taking appropriate action to prevent accidents.

Note

For information about working online and offline, refer to the User Manual

/231/.

Order of Creating

Blocks

Editing during

Program

Execution

Introduction

1 2 ... 18 19 20 21 22 23 24 25 26 27 28 ... 317 318

Sem comentários

Siemens NAN 67 Series Manual de Serviço Página 23