Мануал siemens s7 200

Troubleshooting

Contents

Safety Guidelines

This manual contains notices which you should observe to ensure your own personal safety, as well as to protect the product and connected equipment. These notices are highlighted in the manual by a warning triangle and are marked as follows according to the level of danger:

Danger

Danger indicates an imminently hazardous situation which, if not avoided, will result in death or serious injury.

Warning

Warning indicates a potentially hazardous situation which, if not avoided, could result in death or serious injury.

Caution

Caution used with the safety alert symbol indicates a potentially hazardous situation which, if not avoided, may result in minor or moderate injury.

Caution

Caution used without the safety alert symbol indicates a potentially hazardous situation which, if not avoided, may result in property damage.

Notice

Notice indicates a potential situation which, if not avoided, may result in an undesirable result or state.

Qualified Personnel

Only qualified personnel should be allowed to install and work on this equipment. Qualified persons are defined as persons who are authorized to commission, to ground, and to tag circuits, equipment, and systems in accordance with established safety practices and standards.

Correct Usage

Note the following:

Warning

This device and its components may only be used for the applications described in the catalog or the technical descriptions, and only in connection with devices or components from other manufacturers which have been approved or recommended by Siemens.

This product can only function correctly and safely if it is transported, stored, set up, and installed correctly, and operated and maintained as recommended.

Trademarks

SIMATICR, SIMATIC HMIR and SIMATIC NETR are registered trademarks of SIEMENS AG.

Some of other designations used in these documents are also registered trademarks; the owner’s rights may be violated if they are used by third parties for their own purposes.

Preface

The S7-200 series is a line of micro-programmable logic controllers (Micro PLCs) that can control a variety of automation applications. Compact design, low cost, and a powerful instruction set make the S7-200 a perfect solution for controlling small applications. The wide variety of S7-200 models and the Windows-based programming tool give you the flexibility you need to solve your automation problems.

Audience

This manual provides information about installing and programming the S7-200 Micro PLCs and is designed for engineers, programmers, installers, and electricians who have a general knowledge of programmable logic controllers.

Scope of the Manual

The information contained in this manual pertains in particular to the following products:

—S7-200 CPU models: CPU 221, CPU 222, CPU 224, CPU 226, and CPU 226XM

—S7-200 EM 22x expansion modules

—STEP 7—Micro/WIN, version 3.2, a 32-bit programming software package for the S7-200

—STEP 7—Micro/WIN Instruction Libraries and TP-Designer for TP070, Version 1.0, a set of software tools for customers who use an S7-200 with other components, such as the TP070 Touch Panel, Modbus, or a MicroMaster drive

Standards Compliance

The SIMATIC S7-200 series meets the following standards:

—European Community (CE) Low Voltage Directive 73/23/EEC

EN 61131—2: Programmable Controllers — Equipment requirements

—European Community (CE) EMC Directive 89/336/EEC

Electromagnetic emissions standard

EN 61000—6—3: residential, commercial, and light industry EN 61000—6—4: industrial environment

Electromagnetic immunity standards EN 61000—6—2: industrial environment

—Underwriters Laboratories, Inc.

—Canadian Standards Association: CSA C22.2 Number 142 (Process Control Equipment)

—Factory Mutual Research: FM Class I, Division 2, Groups A, B, C, & D Hazardous Locations, T4A and Class I, Zone 2, IIC, T4

Refer to Appendix A for compliance information.

Tip

The SIMATIC S7-200 series meets the CSA standard.

The cULus logo indicates that the S7-200 has been examined and certified by Underwriters Laboratories (UL) to standards UL 508 and CSA 22.2 No. 142.

Contents

Maritime Approvals

The S7-200 products are periodically submitted for special agency approvals related to specific markets and applications. This table identifies the agency and certificate number that the S7-200 products have been approved for. Not all S7-200 products in this manual have been approved for these special agency approvals. Consult your local Siemens representative if you need additional information related to the latest listing of exact approvals by part number.

How to Use This Manual

If you are a first-time (novice) user of S7-200 Micro PLCs, you should read the entire S7-200 Programmable Controller System Manual. If you are an experienced user, refer to the table of contents or index to find specific information.

The S7-200 Programmable Controller System Manual is organized according to the following topics:

—Chapter 1 (Product Overview) provides an overview of some of the features of the S7-200 family of Micro PLC products.

—Chapter 2 (Getting Started) provides a tutorial for creating and downloading a sample control program to an S7-200.

—Chapter 3 (Installing the S7-200) provides the dimensions and basic guidelines for installing the S7-200 CPU modules and expansion I/O modules.

—Chapter 4 (PLC Concepts) provides information about the operation of the S7-200.

—Chapter 5 (Programming Concepts, Conventions, and Features) provides information about the features of STEP 7—Micro/WIN, the program editors and types of instructions (IEC 1131-3 or SIMATIC), S7-200 data types, and guidelines for creating programs.

—Chapter 6 (S7-200 Instruction Set) provides descriptions and examples of programming instructions supported by the S7-200.

—Chapter 7 (Communicating over a Network) provides information for setting up the different network configurations supported by the S7-200.

—Chapter 8 (Hardware Troubleshooting Guide and Software Debugging Tools) provides information for troubleshooting problems with the S7-200 hardware and about the STEP 7—Micro/WIN features that help you debug your program.

—Chapter 9 (Creating a Program for the Position Module) provides information about the instructions and wizard used to create a program for the EM 253 Position module.

—Chapter 10 (Creating a Program for the Modem Module) provides information about the instructions and wizard used to create a program for the EM 241 Modem module.

—Chapter 11 (Using the USS Protocol Library to Control a MicroMaster Drive) provides information about the instructions used to create a control program for a MicroMaster drive. It also provides information about how to configure the MicroMaster 3 and MicroMaster 4 drives.

—Chapter 12 (Using the Modbus Protocol Library) provides information about the instructions used to create a program that uses the Modbus protocol for communications.

—Appendix A (Technical Specifications) provides the technical information and data sheets about the S7-200 hardware.

The other appendices provide additional reference information, such as descriptions of the error codes, descriptions of the Special Memory (SM) area, part numbers for ordering S7-200 equipment, and STL instruction execution times.

Preface

Additional Information and Assistance

Information about the S7-200 and STEP 7-Micro/WIN

In addition to this manual, STEP 7—Micro/WIN provides extensive online help for getting started with programming the S7-200. Included with the purchase of the STEP 7—Micro/WIN software is a free documentation CD. On this CD you can find application tips, an electronic version of this manual and other information.

Online Help

Help is only a keystroke away! Pressing F1 accesses the extensive online help for STEP 7—Micro/WIN. The online help includes useful information about getting started with programming the S7-200, as well as many other topics.

Electronic Manual

An electronic version of this S7-200 System Manual is available on the documentation CD. You can install the electronic manual onto your computer so that you can easily access the information in the manual while you are working with the STEP 7—Micro/WIN software.

Programming Tips

The documentation CD includes Programming Tips, a set of application examples with sample programs. Reviewing or modifying these examples can help you find efficient or innovative solutions for your own application. You can also find the most current version of Programming Tips on the S7-200 Internet site.

Internet: www.siemens.com/S7—200

For additional information about Siemens products and services, technical support, frequently asked questions (FAQs), product updates, or application tips, refer to the following Internet addresses:

— www.ad.siemens.de for general Siemens information

This Siemens Automation & Drives Internet site includes information about the SIMATIC product line and other products available from Siemens.

—www.siemens.com/S7—200 for S7-200 product information

The S7-200 Internet site includes frequently asked questions (FAQs), Programming Tips (application examples and sample programs), information about newly released products, and product updates or downloads.

Technical Assistance and Purchasing S7-200 Products

Local Siemens Sales Office or Distributor

For assistance in answering any technical questions, for training on the S7-200 products, or for ordering S7-200 products, contact your Siemens distributor or sales office. Because your sales representatives are technically trained and have the most specific knowledge about your operations, process and industry, as well as about the individual Siemens products that you are using, they can provide the fastest and most efficient answers to any problems that you might encounter.

Technical Services

The highly trained staff of the S7-200 Technical Services center is also available to help you solve any problems that you might encounter. You can call on them 24 hours a day, 7 days a week:

—For calls originating from within the United States of America

—For calls originating from the Americas outside of the USA

—For calls originating from Europe and Africa

Local time (Nuremberg): Monday to Friday 0700 to 1700

—For calls originating from Asia and Australia

Contents

Shift and Rotate Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

Shift Right and Shift Left Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

Rotate Right and Rotate Left Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

Shift Register Bit Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

Swap Bytes Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184

String Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

Table Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190

Add To Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190

First-In-First-Out and Last-In-First-Out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191

Memory Fill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

Table Find . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194

Timer Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197

SIMATIC Timer Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197

IEC Timer Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

Subroutine Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204

Features for Debugging Your Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246 Displaying the Program Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 Using a Status Chart to Monitor and Modify the Data in the S7-200 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 Forcing Specific Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 Running Your Program for a Specified Number of Scans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 Hardware Troubleshooting Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251

Features of the Position Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254 Configuring the Position Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256 Position Instructions Created by the Position Control Wizard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 Sample Programs for the Position Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279 Monitoring the Position Module with the EM 253 Control Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284 Error Codes for the Position Module and the Position Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286 Advanced Topics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288

10 Creating a Program for the Modem Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297

Features of the Modem Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298 Using the Modem Expansion Wizard to Configure the Modem Module . . . . . . . . . . . . . . . . . . . . . . . . . 304 Overview of Modem Instructions and Restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308 Instructions for the Modem Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309

Contents

Sample Program for the Modem Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313 S7-200 CPUs that Support Intelligent Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313 Special Memory Location for the Modem Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314 Advanced Topics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316 Messaging Telephone Number Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318 Text Message Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318 CPU Data Transfer Message Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320

11 Using the USS Protocol Library to Control a MicroMaster Drive . . . . . . . . . . . . . . . . . . . 321

Requirements for Using the USS Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322 Calculating the Time Required for Communicating with the Drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323 Using the USS Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324 Instructions for the USS Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325 Sample Programs for the USS Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332 USS Execution Error Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 Connecting and Setting Up the MicroMaster Series 3 Drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334 Connecting and Setting Up the MicroMaster Series 4 Drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337

12 Using the Modbus Protocol Library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339

Requirements for Using the Modbus Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 Initialization and Execution Time for the Modbus Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 Modbus Addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 Using the Modbus Slave Protocol Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 Instructions for the Modbus Slave Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343

Contents

D Special Memory (SM) Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427

SMB0: Status Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428 SMB1: Status Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428 SMB2: Freeport Receive Character . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429 SMB3: Freeport Parity Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429 SMB4: Queue Overflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429 SMB5: I/O Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 430 SMB6: CPU ID Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 430 SMB7: Reserved . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 430 SMB8 to SMB21: I/O Module ID and Error Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 431 SMW22 to SMW26: Scan Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432 SMB28 and SMB29: Analog Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432 SMB30 and SMB130: Freeport Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432 SMB31 and SMW32: Permanent Memory (EEPROM) Write Control . . . . . . . . . . . . . . . . . . . . . . . . . . . 433 SMB34 and SMB35: Time Interval Registers for Timed Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433 SMB36 to SMB65: HSC0, HSC1, and HSC2 Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433 SMB66 to SMB85: PTO/PWM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 435 SMB86 to SMB94, and SMB186 to SMB194: Receive Message Control . . . . . . . . . . . . . . . . . . . . . . . 436 SMW98: Errors on the Expansion I/O Bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437 SMB130: Freeport Control Register (see SMB30) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437 SMB131 to SMB165: HSC3, HSC4, and HSC5 Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437 SMB166 to SMB185: PTO0, PTO1 Profile Definition Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438 SMB186 to SMB194: Receive Message Control (see SMB86 to SMB94) . . . . . . . . . . . . . . . . . . . . . . . 438 SMB200 to SMB549: Intelligent Module Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 439

E S7-200 Order Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441 F Execution Times for STL Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 445 G S7-200 Quick Reference Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 451 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 457

Product Overview

The S7-200 series of micro-programmable logic controllers (Micro PLCs) can control a wide variety of devices to support your automation needs.

The S7-200 monitors inputs and changes outputs as controlled by the user program, which can include Boolean logic, counting, timing, complex math operations, and communications with other intelligent devices. The compact design, flexible configuration, and powerful instruction set combine to make the S7-200 a perfect solution for controlling a wide variety of applications.

S7-200 Programmable Controller System Manual

Figure 1-1 S7-200 Micro PLC

Siemens provides different S7-200 CPU models with a diversity of features and capabilities that help you create effective solutions for your varied applications. Table 1-1 briefly compares some of the features of the CPU. For detailed information about a specific CPU, see Appendix A.

1 You must calculate your power budget to determine how much power (or current) the S7-200 CPU can provide for your configuration. If the CPU power budget is exceeded, you may not be able to connect the maximum number of modules. See Appendix A for CPU and expansion module power requirements, and Appendix B to calculate your power budget.

Product Overview Chapter 1

Table 1-2 S7-200 Expansion Modules

STEP 7-Micro/WIN Programming Package

The STEP 7—Micro/WIN programming package provides a user-friendly environment to develop, edit, and monitor the logic needed to control your application. STEP 7—Micro/WIN provides three program editors for convenience and efficiency in developing the control program for your application. To help you find the information you need, STEP 7—Micro/WIN provides an extensive online help system and a documentation CD that contains an electronic version of this manual, application tips, and other useful information.

Computer Requirements

STEP 7—Micro/WIN runs on either a personal computer or a Siemens programming device, such as a PG 760. Your computer or programming device should meet the following minimum requirements:

—Operating system: Windows 95, Windows 98,

Windows 2000, Windows Me (Millennium Edition), Windows NT 4.0 (or later version),

Windows XP Professional

—At least 100M bytes of free hard disk space

—Mouse (recommended)

Figure 1-2 STEP 7—Micro/WIN

Communications Options

Siemens provides two programming options for connecting your computer to your S7-200: a direct connection with a PPI Multi-Master cable, or a Communications Processor (CP) card with an MPI cable.

The PPI Multi-Master programming cable is the most common and economical method of connecting your computer to the S7-200. This cable connects the communications port of the S7-200 to the serial communications of your computer. The PPI Multi-Master programming cable can also be used to connect other communications devices to the S7-200.

Display Panels

TD 200 Text Display Unit

The TD 200 is a 2-line, 20-character, text display device that can be connected to the S7-200. Using the TD 200 wizard, you can easily program your S7-200 to display text messages and other data pertaining to your application.

The TD 200 provides a low cost interface to your application by allowing you to view, monitor, and change the process variables pertaining to your application.

A separate manual describes the detailed functionality and specifications of the TD 200.

The TD 200 Configuration Wizard in

STEP 7—MicroWIN helps you configure TD 200 messages quickly and easily. To start the TD

menu command.

TP070 Touch Panel Display

The TP070 is a touch panel display device that can be connected to the S7-200. This touch panel provides you with a means to customize your operator interface.

The TP070 can display custom graphics, slider bars, application variables, custom user buttons, and so forth, by means of a user-friendly touch panel.

The optional TP—Designer for TP070, Version 1.0 CD provides the TP Designer software, which is required for programming your TP070.

Figure 1-4 TP070 Touch Panel Unit

Getting Started

STEP 7—Micro/WIN makes it easy for you to program your S7-200. In just a few short steps using a simple example, you can learn how to connect, program, and run your S7-200.

All you need for this example is a PPI Multi-Master cable, an S7-200 CPU, and a programming device running the STEP 7—Micro/WIN programming software.

S7-200 Programmable Controller System Manual

Connecting the S7-200 CPU

DC Installation AC Installation

Figure 2-1 Connecting Power to the S7-200 CPU

Tip

Examples in this manual use the RS-232/PPI Multi-Master cable. The RS-232/PPI Multi-Master cable replaces the previous PC/PPI cable. A USB/PPI Multi-Master cable is also available. Refer to Appendix E for order numbers.

Connecting the RS-232/PPI Multi-Master Cable

S7-200 Programmable Controller System Manual

Verifying the Communications Parameters for STEP 7-Micro/WIN

Establishing Communications with the S7-200

Use the Communications dialog box to connect with your S7-200 CPU:

1. Double-click the refresh icon in the

Getting Started Chapter 2

Creating a Sample Program

Example: Sample Program for getting started with STEP 7-Micro/WIN

Network 1 //10 ms timer T33 times out after (100 x 10 ms = 1 s) //M0.0 pulse is too fast to monitor with Status view.

Network 2 //Comparison becomes true at a rate that is visible with //Status view. Turn on Q0.0 after (40 x 10 ms = 0.4 s), //for a 40% OFF/60% ON waveform.

LDW>= T33, +40

=Q0.0

Network 3 //T33 (bit) pulse too fast to monitor with Status view. //Reset the timer through M0.0 after the

//(100 x 10 ms = 1 s) period.

LD T33

=M0.0

current = 40

T33 (bit)

M0.0

Q0.0

S7-200 Programmable Controller System Manual

Entering Network 1: Starting the Timer

When M0.0 is off (0), this contact turns on and provides power flow to start the timer. To enter the contact for M0.0:

1.Double-click the Timers icon to display the timer instructions.

2.Select the TON (On-Delay Timer).

3.Hold down the left mouse button and drag the timer onto the first network.

4.Click on the “???” above the timer box and enter the following timer number: T33

5.Press the Return key to enter the timer number and to move the focus to the preset time (PT) parameter.

6.Enter the following value for the preset time: 100

7.Press the Return key to enter the value.

Entering Network 2: Turning the Output On

When the timer value for T33 is greater than or equal to 40 (40 times 10 milliseconds, or 0.4 seconds), the contact provides power flow to turn on output Q0.0 of the S7-200. To enter the Compare instruction:

1.Double-click the Compare icon to display the compare instructions. Select the >=I instruction (Greater-Than-Or-Equal-To-Integer ).

2.Hold down the left mouse button and drag the compare instruction onto the second network.

3.Click on the “???” above the contact and enter the address for the timer value: T33

4.Press the Return key to enter the timer number and to move the focus to the other value to be compared with the timer value.

5.Enter the following value to be compared with the timer value: 40

To enter the instruction for turning on output Q0.0:

1.Double-click the Bit Logic icon to display the bit logic instructions and select the output coil.

2.Hold down the left mouse button and drag the coil onto the second network.

3.Click on the “???” above the coil and enter the following address: Q0.0

4.Press the Return key to enter the address for the coil.

Getting Started Chapter 2

Entering Network 3: Resetting the Timer

To enter the coil for turning on M0.0:

1. Select the output coil from the bit logic

instructions. Figure 2-9 Network 3

2.Hold down the left mouse button and drag the output coil onto the third network.

3.Double-click the “???” above the coil and enter the following address: M0.0

4.Press the Return key to enter the address for the coil.

Saving the Sample Project

After entering the three networks of instructions, you have finished entering the program. When you save the program, you create a project that includes the S7-200 CPU type and other parameters. To save the project:

1.Select the File > Save As menu command from the menu bar.

2.Enter a name for the project in the Save As dialog box.

3.Click OK to save the project.

After saving the project, you can download the program to the S7-200.

Figure 2-10 Saving the Example Program

1.Click the Download icon on the toolbar or select the File > Download menu command to download the program. See Figure 2-11.

2.Click OK to download the elements of the program to the S7-200.

If your S7-200 is in RUN mode, a dialog box prompts you to place the S7-200 in STOP mode. Click Yes to place the S7-200 into STOP

mode. Figure 2-11 Downloading the Program

Placing the S7-200 in RUN Mode

For STEP 7—Micro/WIN to place the S7-200 CPU in RUN mode, the mode switch of the S7-200 must be set to TERM or RUN. When you place the S7-200 in RUN mode, the S7-200 executes the program:

1.Click the RUN icon on the toolbar or select the PLC > RUN menu command.

2.Click OK to change the operating mode of the S7-200.

When the S7-200 goes to RUN mode, the

output LED for Q0.0 turns on and off as the

S7-200 executes the program. Figure 2-12 Placing the S7-200 in RUN Mode

Congratulations! You have just completed your first S7-200 program.

You can monitor the program by selecting the Debug > Program Status menu command.

STEP 7—Micro/WIN displays the values for the instructions. To stop the program, place the S7-200 in

STOP mode by clicking the STOP icon or by selecting the PLC > STOP menu command.

Installing the S7-200

The S7-200 equipment is designed to be easy to install. You can use the mounting holes to attach the modules to a panel, or you can use the built-in clips to mount the modules onto a standard (DIN) rail. The small size of the S7-200 allows you to make efficient use of space.

This chapter provides guidelines for installing and wiring your S7-200 system.

S7-200 Programmable Controller System Manual

Guidelines for Installing S7-200 Devices

You can install an S7-200 either on a panel or on a standard rail, and you can orient the S7-200 either horizontally or vertically.

Separate the S7-200 Devices from Heat, High Voltage, and Electrical Noise

When configuring the layout of the S7-200 inside your panel, consider the heat-generating devices and locate the electronic-type devices in the cooler areas of your cabinet. Operating any electronic device in a high-temperature environment will reduce the time to failure.

Consider also the routing of the wiring for the devices in the panel. Avoid placing low voltage signal wires and communications cables in the same tray with AC power wiring and high-energy, rapidly-switched DC wiring.

Provide Adequate Clearance for Cooling and Wiring

S7-200 devices are designed for natural convection cooling. For proper cooling, you must provide a clearance of at least 25 mm above and below the devices. Also, allow at least 75 mm of depth.

Tip

For vertical mounting, the maximum allowable ambient temperature is reduced by 10° C. Mount the S7-200 CPU below any expansion modules.

When planning your layout for the S7-200 system, allow enough clearance for the wiring and communications cable connections. For additional flexibility in configuring the layout of the S7-200 system, use the I/O expansion cable.

DIN Rail

25 mm

Side View

Horizontal DIN Rail Mounting with Optional

Expansion Cable (limit one per system)

Figure 3-1 Mounting Methods, Orientation, and Clearance

Power Budget

All S7-200 CPUs have an internal power supply that provides power for the CPU, the expansion modules, and other 24 VDC user power requirements.

The S7-200 CPU provides the 5 VDC logic power needed for any expansion in your system. Pay careful attention to your system configuration to ensure that your CPU can supply the 5V power required by your selected expansion modules. If your configuration requires more power than the CPU can supply,

you must remove a module or select a CPU with more power capability. Refer to Appendix A for 3 information about the 5 VDC logic budget supplied by your S7-200 CPU and the 5 VDC power

requirements of the expansion modules. Use Appendix B as a guide for determining how much power (or current) the CPU can provide for your configuration.

All S7-200 CPUs also provide a 24 VDC sensor supply that can supply 24 VDC for input points, for relay coil power on the expansion modules, or for other requirements. If your power requirements exceed the budget of the sensor supply, then you must add an external 24 VDC power supply to your system. Refer to Appendix A for the 24 VDC sensor supply power budget for your particular S7-200 CPU.

If you require an external 24 VDC power supply, ensure that the power supply is not connected in parallel with the sensor supply of the S7-200 CPU. For improved electrical noise protection, it is recommended that the commons (M) of the different power supplies be connected.

Warning

Connecting an external 24 VDC power supply in parallel with the S7-200 24 VDC sensor supply can result in a conflict between the two supplies as each seeks to establish its own preferred output voltage level.

The result of this conflict can be shortened lifetime or immediate failure of one or both power supplies, with consequent unpredictable operation of the PLC system. Unpredictable operation could result in death or serious injury to personnel, and/or damage to equipment.

The S7-200 DC sensor supply and any external power supply should provide power to different points.

Installing and Removing the S7-200 Modules

The S7-200 can be easily installed on a standard DIN rail or on a panel.

Prerequisites

Before you install or remove any electrical device, ensure that the power to that equipment has been turned off. Also, ensure that the power to any related equipment has been turned off.

Warning

Attempts to install or remove S7-200 or related equipment with the power applied could cause electric shock or faulty operation of equipment.

Failure to disable all power to the S7-200 and related equipment during installation or removal procedures could result in death or serious injury to personnel, and/or damage to equipment.

Always follow appropriate safety precautions and ensure that power to the S7-200 is disabled before attempting to install or remove S7-200 CPUs or related equipment.

Always ensure that whenever you replace or install an S7-200 device you use the correct module or equivalent device.

Warning

If you install an incorrect module, the program in the S7-200 could function unpredictably.

Failure to replace an S7-200 device with the same model, orientation, or order could result in death or serious injury to personnel, and/or damage to equipment.

Replace an S7-200 device with the same model, and be sure to orient and position it correctly.

S7-200 Programmable Controller System Manual

Mounting Dimensions

The S7-200 CPUs and expansion modules include mounting holes to facilitate installation on panels. Refer to Table 3-1 for the mounting dimensions.

Table 3-1 Mounting Dimensions

Installing a CPU or Expansion Module

Installing the S7-200 is easy! Just follow these steps.

Panel Mounting

1.Locate, drill, and tap the mounting holes (M4 or American Standard number 8), using the dimensions in Table 3-1.

2.Secure the module(s) to the panel, using the appropriate screws.

3.If you are using an expansion module, connect the expansion module ribbon cable into the expansion port connector under the access door.

DIN Rail Mounting

1.Secure the rail to the mounting panel every 75 mm.

2.Snap open the DIN clip (located on the bottom of the module) and hook the back of the module onto the DIN rail.

3.If you are using an expansion module, connect the expansion module ribbon cable into the expansion port connector under the access door.

4.Rotate the module down to the DIN rail and snap the clip closed. Carefully check that the clip has fastened the module securely onto the rail. To avoid damage to the module, press on the tab of the mounting hole instead of pressing directly on the front of the module.

Installing the S7-200 Chapter 3

Tip

Using DIN rail stops could be helpful if your S7-200 is in an environment with high vibration potential or if the S7-200 has been installed vertically.

If your system is in a high-vibration environment, then panel-mounting the S7-200 will provide a greater level of vibration protection.

1.Remove power from the S7-200.

2.Disconnect all the wiring and cabling that is attached to the module. Most S7-200 CPU and expansion modules have removable connectors to make this job easier.

3.If you have expansion modules connected to the unit that you are removing, open the access cover door and disconnect the expansion module ribbon cable from the adjacent modules.

4.Unscrew the mounting screws or snap open the DIN clip.

5.Remove the module.

Removing and Reinstalling the Terminal Block Connector

Most S7-200 modules have removable connectors to make installing and replacing the module easy. Refer to Appendix A to determine whether your S7-200 module has removable connectors. You can order an optional fan-out connector for modules that do not have removable connectors. See Appendix E for order numbers.

To Remove the Connector

1.Open the connector door to gain access to the connector.

2.Insert a small screwdriver in the notch in the middle of the connector.

3.Remove the terminal connector by prying the screwdriver away from the S7-200 housing. See Figure 3-2.

Figure 3-2 Removing the Connector

To Reinstall the Connector

1.Open the connector door.

2.Align the connector with the pins on the unit and align the wiring edge of the connector inside the rim of the connector base.

3.Press down firmly to rotate the connector until it snaps into place. Check carefully to ensure that the connector is properly aligned and fully engaged.

S7-200 Programmable Controller System Manual

Guidelines for Grounding and Wiring

Proper grounding and wiring of all electrical equipment is important to help ensure the optimum operation of your system and to provide additional electrical noise protection for your application and the S7-200.

Installing the S7-200 Chapter 3

Guidelines for Grounding the S7-200

The best way to ground your application is to ensure that all the common and ground connections of your S7-200 and related equipment are grounded to a single point. This single point should be connected directly to the earth ground for your system.

For improved electrical noise protection, it is recommended that all DC common returns be connected to the same single-point earth ground. Connect the 24 VDC sensor supply common (M) to earth ground.

S7-200 Programmable Controller System Manual

Guidelines for Suppression Circuits

You should equip inductive loads with suppression circuits to limit voltage rise when the control output turns off. Suppression circuits protect your outputs from premature failure due to high inductive switching currents. In addition, suppression circuits limit the electrical noise generated when switching inductive loads.

DC Outputs and Relays That Control DC Loads

The DC outputs have internal protection that is adequate for most applications. Since the relays can be used for either a DC or an AC load, internal protection is not provided.

Figure 3-3 shows a sample suppression circuit for a DC load. In most applications, the addition of a diode (A) across the inductive load is suitable, but if your application requires faster turn-off times, then the addition of a Zener diode (B) is recommended. Be sure to size your Zener diode properly for the amount of current in your output circuit.

AC Outputs and Relays That Control AC Loads

The AC outputs have internal protection that is adequate for most applications. Since the relays can be used for either a DC or an AC load, internal protection is not provided.

PLC Concepts

The basic function of the S7-200 is to monitor field inputs and, based on your control logic, turn on or off field output devices. This chapter explains the concepts used to execute your program, the various types of memory used, and how that memory is retained.

S7-200 Programmable Controller System Manual

Understanding How the S7-200 Executes Your Control Logic

The S7-200 continuously cycles through the control logic in your program, reading and writing data.

The S7-200 Relates Your Program to the Physical Inputs and Outputs

The S7-200 Executes Its Tasks in a Scan Cycle

The S7-200 executes a series of tasks repetitively. This cyclical execution of tasks is called the scan cycle. As shown in Figure 4-2, the S7-200 performs most or all of the following tasks during a scan cycle:

—Reading the inputs: The S7-200 copies the state of

—Writing to the outputs: The values stored in the

The execution of the scan cycle is dependent upon whether the S7-200 is in STOP mode or in RUN mode. In RUN mode, your program is executed; in STOP mode, your program is not executed.

PLC Concepts Chapter 4

Reading the Inputs

Digital inputs: Each scan cycle begins by reading the current value of the digital inputs and then writing these values to the process-image input register.

Analog inputs: The S7-200 does not update analog inputs as part of the normal scan cycle unless filtering of analog inputs is enabled. An analog filter is provided to allow you to have a more stable signal. You can enable the analog filter for each analog input point.

When analog input filtering is enabled for an analog input, the S7-200 updates that analog input once per scan cycle, performs the filtering function, and stores the filtered value internally. The filtered value is then supplied each time your program accesses the analog input.

S7-200 Programmable Controller System Manual

Accessing the Data of the S7-200

The S7-200 stores information in different memory locations that have unique addresses. You can explicitly identify the memory address that you want to access. This allows your program to have direct access to the information. Table 4-1 shows the range of integer values that can be represented by the different sizes of data.

To access a bit in a memory area, you specify the address, which includes the memory area identifier, the byte address, and the bit number. Figure 4-3 shows an example of accessing a bit (which is also called “byte.bit” addressing). In this example, the memory area and byte address (I = input, and 3 = byte 3) are followed by a period (“.”) to separate the bit address (bit 4).

You can access data in most memory areas (V, I, Q, M, S, L, and SM) as bytes, words, or double words by using the byte-address format. To access a byte, word, or double word of data in the memory, you must specify the address in a way similar to specifying the address for a bit. This includes an area identifier, data size designation, and the starting byte address of the byte, word, or double-word value, as shown in Figure 4-4.

Data in other memory areas (such as T, C, HC, and the accumulators) are accessed by using an address format that includes an area identifier and a device number.

Accessing Data in the Memory Areas

Process-Image Input Register: I

The S7-200 samples the physical input points at the beginning of each scan cycle and writes these values to the process-image input register. You can access the process-image input register in bits, bytes, words, or double words:

Process-Image Output Register: Q

At the end of the scan cycle, the S7-200 copies the values stored in the process-image output register to the physical output points. You can access the process-image output register in bits, bytes, words, or double words:

Variable Memory Area: V

You can use V memory to store intermediate results of operations being performed by the control logic in your program. You can also use V memory to store other data pertaining to your process or task. You can access the V memory area in bits, bytes, words, or double words:

Bit Memory Area: M

You can use the bit memory area (M memory) as control relays to store the intermediate status of an operation or other control information. You can access the bit memory area in bits, bytes, words, or double words:

S7-200 Programmable Controller System Manual

Timer Memory Area: T

The S7-200 provides timers that count increments of time in resolutions (time-base increments) of 1 ms, 10 ms, or 100 ms. Two variables are associated with a timer:

—Current value: this 16-bit signed integer stores the amount of time counted by the timer.

—Timer bit: this bit is set or cleared as a result of comparing the current and the preset value. The preset value is entered as part of the timer instruction.

You access both of these variables by using the timer address (T + timer number). Access to either the timer bit or the current value is dependent on the instruction used: instructions with bit operands access the timer bit, while instructions with word operands access the current value. As shown in Figure 4-5, the

4 Normally Open Contact instruction accesses the timer bit, while the Move Word instruction accesses the current value of the timer.

Counter Memory Area: C

The S7-200 provides three types of counters that count each low-to-high transition event on the counter input(s): one type counts up only, one type counts down only, and one type counts both up and down. Two variables are associated with a counter:

—Current value: this 16-bit signed integer stores the accumulated count.

—Counter bit: this bit is set or cleared as a result of comparing the current and the preset value. The preset value is entered as part of the counter instruction.

You access both of these variables by using the counter address (C + counter number). Access to either the counter bit or the current value is dependent on the instruction used: instructions with bit operands access the counter bit, while instructions with word operands access the current value. As shown in Figure 4-6, the Normally Open Contact instruction accesses the counter bit, while the Move Word instruction accesses the current value of the counter.

Figure 4-6 Accessing the Counter Bit or the Current Value of a Counter

High-Speed Counters: HC

The high-speed counters count high-speed events independent of the CPU scan. High-speed counters have a signed, 32-bit integer counting value (or current value). To access the count value for the high-speed counter, you specify the address of the high-speed counter, using the memory type (HC) and the counter number (such as HC0). The current value of the high-speed counter is a read-only value and can be addressed only as a double word (32 bits).

Accumulators: AC

The accumulators are read/write devices that can be used like memory. For example, you can use

accumulators to pass parameters to and from subroutines and to store intermediate values used in a 4 calculation. The S7-200 provides four 32-bit accumulators (AC0, AC1, AC2, and AC3). You can access

the data in the accumulators as bytes, words, or double words.

The size of the data being accessed is determined by the instruction that is used to access the accumulator. As shown in Figure 4-7, you use the least significant 8 or 16 bits of the value that is stored in the accumulator to access the accumulator as bytes or words. To access the accumulator as a double word, you use all 32 bits.

For information about how to use the accumulators within interrupt subroutines, refer to the Interrupt Instructions in Chapter 6.

Figure 4-7 Accessing the Accumulators

S7-200 Programmable Controller System Manual

Special Memory: SM

The SM bits provide a means for communicating information between the CPU and your program. You can use these bits to select and control some of the special functions of the S7-200 CPU, such as: a bit that turns on for the first scan cycle, a bit that toggles at a fixed rate, or a bit that shows the status of math or operational instructions. (For more information about the SM bits, see Appendix D.) You can access the SM bits as bits, bytes, words, or double words:

Local Memory Area: L

4 The S7-200 provides 64 bytes of local memory of which 60 can be used as scratchpad memory or for passing formal parameters to subroutines.

Tip

If you are programming in either LAD or FBD, STEP 7—Micro/WIN reserves the last four bytes of local memory for its own use. If you program in STL, all 64 bytes of L memory are accessible, but it is recommended that you do not use the last four bytes of L memory.

Local memory is similar to V memory with one major exception. V memory has a global scope while L memory has a local scope. The term global scope means that the same memory location can be accessed from any program entity (main program, subroutines, or interrupt routines). The term local scope means that the memory allocation is associated with a particular program entity. The S7-200 allocates 64 bytes of L memory for the main program, 64 bytes for each subroutine nesting level, and 64 bytes for interrupt routines.

The allocation of L memory for the main program cannot be accessed from subroutines or from interrupt routines. A subroutine cannot access the L memory allocation of the main program, an interrupt routine, or another subroutine. Likewise, an interrupt routine cannot access the L memory allocation of the main program or of a subroutine.

The allocation of L memory is made by the S7-200 on an as-needed basis. This means that while the main portion of the program is being executed, the L memory allocations for subroutines and interrupt routines do not exist. At the time that an interrupt occurs or a subroutine is called, local memory is allocated as required. The new allocation of L memory might reuse the same L memory locations of a different subroutine or interrupt routine.

The L memory is not initialized by the S7-200 at the time of allocation and might contain any value. When you pass formal parameters in a subroutine call, the values of the parameters being passed are placed by the S7-200 in the appropriate L memory locations of the called subroutine. L memory locations, which do not receive a value as a result of the formal parameter passing step, will not be initialized and might contain any value at the time of allocation.

Analog Inputs: AI

The S7-200 converts an analog value (such as temperature or voltage) into a word-length (16-bit) digital value. You access these values by the area identifier (AI), size of the data (W), and the starting byte address. Since analog inputs are words and always start on even-number bytes (such as 0, 2, or 4), you access them with even-number byte addresses (such as AIW0, AIW2, or AIW4). Analog input values are read-only values.

Analog Outputs: AQ

The S7-200 converts a word-length (16-bit) digital value into a current or voltage, proportional to the

digital value (such as for a current or voltage). You write these values by the area identifier (AQ), size of 4 the data (W), and the starting byte address. Since analog outputs are words and always start on

even-number bytes (such as 0, 2, or 4), you write them with even-number byte addresses (such as AQW0, AQW2, or AQW4). Analog output values are write-only values.

Sequence Control Relay (SCR) Memory Area: S

SCRs or S bits are used to organize machine operations or steps into equivalent program segments. SCRs allow logical segmentation of the control program. You can access the S bits as bits, bytes, words, or double words.

Format for Real Numbers

Real (or floating-point) numbers are represented as 32-bit, single-precision numbers, whose format is described in the ANSI/IEEE 754—1985 standard. See Figure 4-8. Real numbers are accessed in double-word lengths.

For the S7-200, floating point numbers are accurate up to 6 decimal places. Therefore, you can specify a maximum of 6 decimal places when entering a floating-point constant.

Accuracy when Calculating Real Numbers

Calculations that involve a long series of values including very large and very small numbers can produce inaccurate results. This can occur if the numbers differ by 10 to the power of x, where x > 6.

S7-200 Programmable Controller System Manual

Format for Strings

A string is a sequence of characters, with each character being stored as a byte. The first byte of the string defines the length of the string, which is the number of characters. Figure 4-9 shows the format for a string. A string can have a length of 0 to 254 characters, plus the length byte, so the maximum length for a string is 255 bytes.

Specifying a Constant Value for S7-200 Instructions

You can use a constant value in many of the S7-200 instructions. Constants can be bytes, words, or double words. The S7-200 stores all constants as binary numbers, which can then be represented in decimal, hexadecimal, ASCII, or real number (floating point) formats. See Table 4-2.

Tip

The S7-200 CPU does not support “data typing” or data checking (such as specifying that the constant is stored as an integer, a signed integer, or a double integer). For example, an Add instruction can use the value in VW100 as a signed integer value, while an Exclusive Or instruction can use the same value in VW100 as an unsigned binary value.

Addressing the Local and Expansion I/O

The local I/O provided by the CPU provides a fixed set of I/O addresses. You can add I/O points to the S7-200 CPU by connecting expansion I/O modules to the right side of the CPU, forming an I/O chain. The addresses of the points of the module are determined by the type of I/O and the position of the module in the chain, with respect to the preceding input or output module of the same type. For example, an output module does not affect the addresses of the points on an input module, and vice versa. Likewise, analog modules do not affect the addressing of digital modules, and vice versa.

Tip

Digital expansion modules always reserve process-image register space in increments of eight bits

(one byte). If a module does not provide a physical point for each bit of each reserved byte, these 4 unused bits cannot be assigned to subsequent modules in the I/O chain. For input modules, the

unused bits in reserved bytes are set to zero with each input update cycle.

Analog expansion modules are always allocated in increments of two points. If a module does not provide physical I/O for each of these points, these I/O points are lost and are not available for assignment to subsequent modules in the I/O chain.

Figure 4-10 provides an example of the I/O numbering for a particular hardware configuration. The gaps in the addressing (shown as gray italic text) cannot be used by your program.

Figure 4-10 Sample I/O Addresses for Local and Expansion I/O (CPU 224)

S7-200 Programmable Controller System Manual

Using Pointers for Indirect Addressing of the S7-200 Memory Areas

Indirect addressing uses a pointer to access the data in memory. Pointers are double word memory locations that contain the address of another memory location. You can only use V memory locations, L memory locations, or accumulator registers (AC1, AC2, AC3) as pointers. To create a pointer, you must use the Move Double Word instruction to move the address of the indirectly addressed memory location to the pointer location. Pointers can also be passed to a subroutine as a parameter.

The S7-200 allows pointers to access the following memory areas: I, Q, V, M, S, T (current value only), and C (current value only). You cannot use indirect addressing to access an individual bit or to access AI, AQ, HC, SM, or L memory areas.

preceded with an ampersand (&) to signify that the address of a memory location, instead of its contents, is to be moved into the location identified in the output operand of the instruction (the pointer).

Entering an asterisk (*) in front of an operand for an instruction specifies that the operand is a pointer. As shown in Figure 4-11, entering *AC1 specifies that AC1 is a pointer to the word-length value being referenced by the Move Word (MOVW) instruction. In this example, the values stored in both VB200 and VB201 are moved to accumulator AC0.

Figure 4-11 Creating and Using a Pointer

As shown in Figure 4-12, you can change the value of a pointer. Since pointers are 32-bit values, use double-word instructions to modify pointer values. Simple mathematical operations, such as adding or incrementing, can be used to modify pointer values.

Figure 4-12 Modifying a Pointer

Tip

Remember to adjust for the size of the data that you are accessing: to access a byte, increment the pointer value by 1; to access a word or a current value for a timer or counter, add or increment the pointer value by 2; and to access a double word, add or increment the pointer value by 4.

PLC Concepts Chapter 4

Sample Program for Using a Pointer to Access Data in a Table

This example uses LD14 as a pointer to a recipe stored in a table of recipes that begins at VB100. In this example, VW1008 stores the index to a specific recipe in the table. If each recipe in the table is 50 bytes long, you multiply the index by 50 to obtain the offset for the starting address of a specific recipe. By adding the offset to the pointer, you can access the individual recipe from the table. In this example, the recipe is copied to the 50 bytes that start at VB1500.

Network 1 //How to transfer a recipe from a table of recipes:

//— Each recipe is 50 bytes long.

//— The index parameter (VW1008) identifies the recipe

//to be loaded.

//

//1. Create a pointer to the starting address of the recipe table. //2. Convert the index of the recipe to a double-word value. //3. Multiply the offset to accommodate the size of each recipe. //4. Add the adjusted offset to the pointer.

//5. Transfer the selected recipe to VB1500 through VB1549.

S7-200 Programmable Controller System Manual

Understanding How the S7-200 Saves and Restores Data

The S7-200 provides a variety of safeguards to ensure that your program, the program data, and the configuration data for your S7-200 are properly retained.