ISA PROFIBUS PCKT GUD-2004 Profibus A Pocket Guide.pdf

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1、PROFIBUSA pocket guideProfibus04.book Page i Wednesday, September 24, 2003 10:49 AMProfibus04.book Page ii Wednesday, September 24, 2003 10:49 AMPROFIBUSA pocket guideby Ron MitchellProfibus04-front.fm Page iii Wednesday, May 31, 2006 2:56 PMCopyright 2004ISAThe Instrumentation, Systems and Automati

2、on Society67 Alexander DriveP.O. Box 12277Research Triangle Park, NC 27709All rights reserved. Printed in the United States of America.1098765432ISBN 1-55617-862-XNo part of this work may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, elec-tronic, mechanical

3、, photocopying, recording or otherwise, without the prior written permission of the publisher.Library of Congress Cataloging-in-Publication Data Data is in Progress ISA wishes to acknowledge the cooperation of those manufac-turers, suppliers, and publishers who granted permission to reproduce materi

4、al herein. The Society regrets any omission of credit that may have occurred and will make such corrections in future editions.Profibus04.book Page iv Wednesday, September 24, 2003 10:49 AMNoticeThe information presented in this publication is for the general education of the reader. Because neither

5、 the author nor the publisher has any control over the use of the informa-tion by the reader, both the author and the publisher disclaim any and all liability of any kind arising out of such use. The reader is expected to exercise sound professional judgment in using any of the information presented

6、 in a particular applica-tion. Additionally, neither the author nor the publisher have investigated or considered the effect of any patents on the abil-ity of the reader to use any of the information in a particular application. The reader is responsible for reviewing any possi-ble patents that may

7、affect any particular use of the informa-tion presented. Any references to commercial products in the work are cited as examples only. Neither the author nor the publisher endorses any referenced commercial product. Any trademarks or tradenames referenced belong to the respective owner of the mark o

8、r name. Neither the author nor the publisher makes any representation regarding the availability of any referenced commercial product at any time. The manufacturers instruc-tions on use of any commercial product must be followed at all times, even if in conflict with the information in this publi-ca

9、tion.Profibus04.book Page v Wednesday, September 24, 2003 10:49 AMProfibus04.book Page vi Wednesday, September 24, 2003 10:49 AMI would like to recognize the people that played a role in the development of this pocket guide. I would partic-ularly like to thank the people with whom I have worked in t

10、he PROFIBUS Interface Center, primarily Rainer Friess and Robert Freller, from whom I learned so much about PROFIBUS. I would also like to thank the people from Siemens and the PROFIBUS Interface Center who participated in reviewing this pocket guide and providing feedback: Josef Braun, Frank Garrab

11、rant, Mike Hales, Claude Hestroffer, and John Swindall.This pocket guide is dedicated to those people in my life who are most important: my wife Wanda, my daugh-ters Krista and Kyme, especially to my son, Kevin, and all of my extended family.Ron Mitchell, 2003Profibus04-front.fm Page vii Monday, Oct

12、ober 6, 2003 3:33 PMProfibus04.book Page viii Wednesday, September 24, 2003 10:49 AMTABLE OF CONTENTS ixTable of ContentsList of Figures. xiList of TablesxvForeword xviiChapter 1Basics of PROFIBUS Operation 11.1 Master/Slave Concept 51.2 Device and System Startup.61.3 Cyclic I/O Data Exchange .121.4

13、 Device Diagnostic Reporting .141.5 Fail-Safe Operation .171.6 Optional Device Functionality 18Chapter 2System Setup 212.1 Configuration Tools .212.2 The Mysterious GSD File.242.3 Device I/O Configuration however, Figure 1-1 lists Profibus04.book Page 2 Wednesday, September 24, 2003 10:49 AMBASICS O

14、F PROFIBUS OPERATION 3the extensions that have been standardized in the past few years.Figure 1-1 PROFIBUS DP ExtensionsAs Figure 1-1 shows, DPV0 is the foundation for PROFIBUS and was the first version after FMS. DPV0 came from optimizations to FMS, the original PROFIBUS protocol, to support fast I

15、/O data exchange. PROFIBUS DPV1 added extensions that allowed run-time reading/writing of parameters for more sophisticated devices such as intelligent drives, for example, and PROFIBUS PA field instruments, such as valve positioners, pressure transmitters, and so on. DPV2 added extensions primarily

16、 so that motion-control applications can be performed Profibus04.book Page 3 Wednesday, September 24, 2003 10:49 AM4 BASICS OF PROFIBUS OPERATIONdirectly across PROFIBUS rather than requiring a secondary motion-control bus.This first chapter will give you a brief overview of the cyclic I/O data exch

17、ange (DPV0) opera-tion of a PROFIBUS network. It will not deal with how you set up the network to operate. Chapter 2 will discuss that topic. Here, we will cover four basic aspects of a PROFIBUS DP net-work:Master/Slave Concept: A general overview of device interactions.Device and System Startup: Ju

18、st how does the master get all those devices and the sys-tem into “operational” mode for control?Cyclic I/O Data Exchange: What the net-work normally does when it is humming along at up to 12,000kbit/s.Device Diagnostic Reporting: What diag-nostics can a device report and what does a device do when

19、it detects a diagnostic con-dition, for example, a wire break on an out-put point?Profibus04.book Page 4 Wednesday, September 24, 2003 10:49 AMBASICS OF PROFIBUS OPERATION 51.1 Master/Slave ConceptPROFIBUS DP is a network that is made up of two types of devices connected to the bus: mas-ter devices

20、and slave devices. It is a bi-directional network, meaning that one device, a master, sends a request to a slave, and the slave responds to that request. Thus, bus contention is not a problem because only one master can control the bus at any time, and a slave device must respond immediately to a re

21、quest from a master. Since a request from a master to a slave device is heard by all devices attached to the bus, some mechanism must exist for a slave device to rec-ognize that a message is designated for it and then respond to the sender. Hence, each device on a PROFIBUS network must have an assig

22、ned address. For specifying the address, most devices have either rotary switches (decimal or hexadeci-mal) or DIP switches. Some few devices require that their address be set across the bus using a configuration tool. This concept will be dis-cussed in the next chapter.The PROFIBUS protocol support

23、s addresses from 0 to 127. However, addresses 126 and 127 have special uses (discussed in Chapter 2) and Profibus04.book Page 5 Wednesday, September 24, 2003 10:49 AM6 BASICS OF PROFIBUS OPERATIONmay not be assigned to operational devices. Address 0 has become something of a default address that ven

24、dors assign to network configu-ration and/or programming tools attached to the bus. Thus, the addresses that may be used in practice for operational devices for example, PLCs, I/O nodes, drives, encoders, and the like are 1 to 125.1.2 Device and System StartupThe user specifies which slave devices t

25、he master should find on the bus as well as what informa-tion is to be transferred from the master to each slave during this startup phase. (Relaxthis is much easier than you might think!) All of the information that the master must know to start up the bus comes from a configuration database file t

26、hat is generated by a PROFIBUS configura-tion tool.Each vendor of PROFIBUS master devices offers a configuration tool for generating the database file for their masters. However, once one has learned how to use any of these tools, it is gener-ally quite easy to transfer this knowledge to another too

27、l because all PROFIBUS configura-Profibus04.book Page 6 Wednesday, September 24, 2003 10:49 AMBASICS OF PROFIBUS OPERATION 7tion tools must share certain common function-ality. A configuration tool for cyclic I/O operation must be able to do the following:process GSD (device description) files and m

28、aintain a hardware catalog of devices to be configured on the busallow the PROFIBUS device address to be specifiedallow the specification of the input and out-put data to be transferred between master and slave allow certain startup parameters to be selected in order to activate specific operat-ing

29、modes or features of the deviceallow selection of the system baud rategenerate the database file so it can be used by the masterAt the same time a vendor develops a slave device, it must develop a device description (GSD) file. This file completely describes the PROFIBUS functionality of the device

30、for example, baud rates supported, possible input/Profibus04.book Page 7 Wednesday, September 24, 2003 10:49 AM8 BASICS OF PROFIBUS OPERATIONoutput data configurations, startup parameter choices, and so on. These GSD files can typi-cally be downloaded via the Internet either from or from an individ

31、ual ven-dors web site. Once you “install” the GSD file for a device into the PROFIBUS configuration tool, it will appear in the tools hardware catalog, which enables it to be configured for bus opera-tion. The installation process varies for different con-figuration tools, although it is extremely s

32、imple in any case. In some tools, installation consists of nothing more than copying the GSD file into a “gsd subdirectory,” while in others one simply “imports” the new GSD file into the hardware catalog by selecting that option from a menu.Once all the appropriate GSD files are installed into the

33、configuration tool, you can define a bus configuration. This is a straightforward process. You first pick the appropriate master from the master device list in the hardware catalog and assign a PROFIBUS address. Not surprisingly, you will generally see only master devices from a specific vendor with

34、in that vendors configura-tion tool! This is nothing to be concerned Profibus04.book Page 8 Wednesday, September 24, 2003 10:49 AMBASICS OF PROFIBUS OPERATION 9about. We are really only concerned that the tool process the standard GSD files for slave devices, and it is required to do this. You repea

35、t the following steps until the entire bus configu-ration has been described: Select a slave device, assign the PROFIBUS address, specify the I/O to be exchanged, and select the appropriate parameters for the desired operation of the device. You then save this bus configuration file and generate the

36、 configuration database.You can now load this configuration database file into the master device. The mechanism for loading the database file into the master may vary with each vendor. The most common mechanism is to download the file into the mas-ter via a serial port. Some configuration tools allo

37、w you to load the file into a flash memory card that is then inserted into the master for download. Some older systems required an EPROM to be programmed and then inserted into the master for download. No matter what mechanism is used, after download, the master has the information necessary to star

38、t up all the devices in its configuration. This information is stored in retentive memory. Figure 1-2 depicts Profibus04.book Page 9 Wednesday, September 24, 2003 10:49 AM10 BASICS OF PROFIBUS OPERATIONthe functionality of a PROFIBUS configuration tool.Figure 1-2 PROFIBUS Configuration Tool Function

39、alityThe master must now determine if the devices at the assigned addresses contained within the con-figuration database are physically on the bus and initialize them for “operational” or “data-exchange ” mode. To get the devices into this mode a PROFIBUS master goes through a well-defined sequence

40、of interactions with each of the slave devices in its bus configuration.Figure 1-3 shows the steps in the startup sequence for a slave device. For instance, if the master device experiences a power loss, when it powers back up it uses the configuration data-Profibus04.book Page 10 Wednesday, Septemb

41、er 24, 2003 10:49 AMBASICS OF PROFIBUS OPERATION 11base in retentive memory to go through the star-tup sequence with each device in its config-uration to get all devices back into operational mode. If a slave device fails and must be replaced, the master recognizes that a replace-ment device of the

42、same type and with the same PROFIBUS address has been attached to the bus. When it does, it goes through this same startup sequence and automatically brings the device into operational mode. VoilPlug & Work!Figure 1-3 Slave Startup SequenceProfibus04.book Page 11 Wednesday, September 24, 2003 10:49

43、AM12 BASICS OF PROFIBUS OPERATION1.3 Cyclic I/O Data ExchangeAfter the bus system has been “started up”, the normal interaction between a master and each of its assigned slaves is to exchange I/O data, as shown in Figure 1-4. The master, a PLC with a PROFIBUS interface, for example, sends output dat

44、a to a slave device in its configuration. The addressed slave immediately responds with its input data. It is important to grasp this concept of output data sent from the master to the slave and input data returned from the slave to the master. This “directional” attribute of the I/O is identical to

45、 I/O that is hardwired directly to backplane I/O in a PLC rack. It typically maps into the input and output areas of PLC memory, as shown in Figure 1-5, and can generally be accessed by the PLC logic program in exactly the same way as backplane I/O. This cyclic (repeated) I/O data exchange takes pla

46、ce asynchronously to the con-trol logic scan and is repeated as quickly as possi-ble. Data exchange takes place every cycle for every slave in a masters configuration. At the most com-monly used baud rate of 1,500kbit/s, data-exchange cycles are normally repeated many times during a single control-logic scan. Profibus04.book Page 12 Wednesday, September 24, 2003 10:49 AM