®

PRO CESS FIELD BUS

PROFIBUS

Specification

Normative Parts

of PROFIBUS -FMS, -DP, -PA according to the European Standard EN 50 170 Volume 2

Edition 1.0

March 1998

PROFIBUS Specification, Order No. 0.032

page 2 PROFIBUS-Specification-Normative-Parts-1:1997

Foreword

PROFIBUS is a fieldbus system, which is in widespread use all over the world. PROFIBUS fulfils the requirements for the interconnection of intelligent field devices in manufacturing, process and building automation.

This publication contains the normative parts of the PROFIBUS-FMS / -DP / -PA specification according to the European fieldbus standard EN 50 170. These normative parts are supplemented by profiles and guidelines of the PROFIBUS user organisation (PNO). Both, the normative parts as well as the profiles and guidelines are published by PROFIBUS International, a world-wide organisation of more than 650 users of the PROFIBUS technology. PROFIBUS International is represented by regional user groups in 20 important industrial countries (see annex).

PROFIBUS has been selected by CENELEC TC65CX to be standardised as European Standard EN 50170 Volume 2 on 1996-07-02. Therefore, the PROFIBUS specification has been included without changes in EN 50170. This document is technical identical to the European Standard EN 50 170 volume 2 and is organised in the same manner.

PROFIBUS International

Business Office

Haid-und-Neu-Strasse 7

D-76131 Karlsruhe / Germany

Tel: ++ 49 721 9658 590

Fax: ++ 49 721 9658 589

email: [e-mail]

Internet: http://www.profibus.com

© Copyright by PNO 1997 - all rights reserved

page 3 PROFIBUS-Specification-Normative-Parts-1:1997

Table of Contents of the Normative Parts of the PROFIBUS Specification

		Page
Part 1	General Description of the Normative Parts	5
Part 2	Physical Layer Specification and Service Definition	13
Part 3	Data Link Layer Service Definition	49
Part 4	Data Link Layer Protocol Specification	97
	(protocol is specified together with services in 3-2)
Part 5	Application Layer Service Definition	139
Part 6	Application Layer Protocol Specification	315
Part 7	Network Management	591
Part 8	User Specifications	687
Part 9	Physical Layer and Data Link Layer for Process Automation	885

Annex Members

Annex BookShop

Annex Support

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PROFIBUS Specification - Normative Parts

Part 1

General Description of the Normative Parts

© Copyright by PNO 1997 - all rights reserved

		page 6
	PROFIBUS-Specification-Normative-Parts-1:1997
	Contents
		Page
1	General Description of the Normative Parts	...........................7
1.1	OSI Environment and layers defined ...................................	7
1.2	Overview about the layers covered ....................................	9
1.2.1	Physical Layer .......................................................	9
1.2.2	Data Link Layer ......................................................	9
1.2.3	Application Layer ...................................................	10
1.2.4	User specifications .................................................	11

© Copyright by PNO 1997 - all rights reserved

page 7 PROFIBUS-Specification-Normative-Parts-1:1997

1 General Description of the Normative Parts

This description provides an overview on the models, services and characteristics of the PROFIBUS System.

1.1 OSI Environment and layers defined

The layered structure is based on the ISO/OSI model for open systems communication (ISO 7498) according to figure 1. This specification defines Layer 1 (Physical Layer, PHY), Layer 2 (Data Link Layer, FDL) and Layer 7 (Application Layer). The Layers 3 to 6 are empty to minimize expense and increase efficiency.

	From/to Application
		^
^		!
!	!	!
FMS Services		FMA7 Services
!	!	!
!	v	v

+	-----------------------------------		+---------------		+
!	F M S		!		!
!			!		!
!... ..	Application Layer .. (Layer 7)		+....	F M A 7	!
!			!		!
!	L L I		!		!
!			!	M	!
+---------------------------------------			+	a	!
!			!	n	!
!	empty	(Layer 3 to 6)	!	a	!
!			!	g	!
+---------------------------------------			+----	e ----+
!			!	m	!
!	Data Link Layer	(Layer 2)	!	e	!
!			!	n	!
!	F D L		!	t	!
!			!		!
+---------------------------------------			+ F M A 1/2 !
!			!		!
!	Physical Layer	(Layer 1)	!		!
!			!		!
!	P H Y		!		!
+--------------------- -----------------		+	+-----------		+
		!
		!

=========================#=================================

Figure 1. OSI environment

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page 8 PROFIBUS-Specification-Normative-Parts-1:1997

This specification defines the technical and functional characteristics of a serial fieldbus which is aimed at the inter-connection of digital field devices or systems with low or medium performance, e.g. sensors, actuators, transmitters, programmable logical controllers (PLC), numerical controllers (NC), programming devices, local man machine interfaces etc.

Often a field control system is based on a central control and supervision unit, which is connected to a number of devices and small systems distributed in the field. In such cases the dominant data transfer is centrally oriented and cyclic from the field devices to the central data processing unit or to a superior control system.

Strict realtime requirements have been met using the following simplifications:

-segmentation of long messages (> 235 byte) is not supported.

-blocking of short messages is not supported. The combination of many short messages into one long message packet is not in accordance with the requirement of short messages, and therefore the specification does not provide this function.

-support of routing functions by the network layer is not provided in the specification.

-	except for a mandatory minimum configuration, arbitrary subsets of		services
	can be created depending on the application requirements. This is a particu-
	larly important	aspect for small systems (sensors, etc.).
-	other functions	are optional such as password protection schemes.
-	the network topology is a linear bus with or without terminator,		including
	drop cables and	branches (tree)

-the medium, distances, number of stations Depending on the signal characteristics, e.g. for shielded twisted pair, ≤ 1,2 km without repeaters, 32 stations

-transmission speed depends on network topology and line lengths, e.g. stepwise from 9,6 to 1500 kbit/s

-a second medium (redundancy) is optional

-a halfduplex, asynchronous, slip protected synchronization (no bit stuffing) is used for transmission

-Data integrity of messages is Hamming distance (HD)=4, sync slip detection, special sequence to avoid loss and multiplication of data

-Addresses are defined in the range of 0 to 127 (127 = global addresses for broad-cast and multicast messages), address extension for regional address,

segment address and Service Access address (Service Access Point, LSAP), 6 bit each

- two station types are used: (1) Masters (active stations, with bus access control), (2) Slaves (passive stations, without bus access control); preferably at most 32 masters, optionally up to 127, if the applications are not time critical.

-Bus access is based on a hybrid, decentral/central method; token passing between master stations and master-slave between master and slave stations. The token circulates in a logical ring formed by the masters. If the system contains only one master, e.g. a central control and supervision station, no token passing is necessary. This is a pure single-master/n-slave system. The minimum configuration comprises one master and one slave, or two masters.

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page 9 PROFIBUS-Specification-Normative-Parts-1:1997

-Data transfer services are

(1)Acyclic:

Send Data with/without Acknowledge Send and Request Data with Reply

(2)Cyclic (Polling):

Send and Request Data with Reply

1.2Overview about the layers covered

The following describes the functionality of the various layers.

1.2.1 Physical Layer

The Physical Layer (this is the medium, including lengths and topology, the line interface, the number of stations and the transmission speed, variable in the range from 9,6 to 1500 kbit/s) can be adapted to different applications. However there is a common access method and transmission protocol and there are common services at the user interface.

The Physical Layer (version 1, contained in Part 2 of this specification) is specified according to the EIA standard RS-485:

- Topology	: Linear bus, terminated at both ends, stubs ≤ 0,3 m, no
		branches;
- Medium	: Shielded Twisted Pair
- Line Length	: ≤ 1200 m
- Number of stations	:	32 (master stations, slave stations or repeaters)
- Data rates	:	9,6 / 19,2 / 93,75 / 187,5 / 500 / 1500 kbit/s

The version 2 (according to IEC 1158-2, contained in Part 9 of this specification) covers the requirements of Intrinsic Safety (IS):

- Topology			:	Linear bus, terminated at	both ends, spurs ≤ 120 m
- Medium			:	Twisted Pair or multicore	(shielded or unshielded)
- Line		Length	:	≤ 1900 m depending on cable type
-	Number of stations		:	32 (master stations, slave stations or repeaters)
-	Data	rates	:	31,25 kbit/s

1.2.2 Data Link Layer

The Medium Access Control protocol (MAC), the data transfer services and the management services are defined according to the standards DIN 19 241-2, IEC 955(PROWAY C), ISO 8802-2 and ISO/IEC JTC 1/SC 6N 4960 (LLC type 1 and LLC type 3).

The octet (character) format shall be the UART format FT 1.2 (asynchronous transmission with start-stop synchronization) as defined for Telecontrol Equipment and Systems (IEC 870-5-1). The transmission protocol definitions are based on the standard IEC 870-5-2.

The following data transfer services are defined:

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Send Data with Acknowledge (SDA)

This service allows an user to send data to a single remote station. If an error occurred, the data transfer shall be repeated.

Send Data with No Acknowledge (SDN)

This service allows an user to transfer data to a single remote station, to many remote stations (Multicast), or to all remote stations (Broadcast) at the same time without any confirmation.

Send and Request Data with Reply (SRD)

This service allows an user to transfer data to a single remote station and at the same time to request data from the remote station. If an error occured, the data transfer shall be repeated.

Cyclic Send and Request Data with Reply (CSRD)

This service allows an User to cyclically transfer data to a remote station and at the same time to request data from the remote station.

1.2.3 Application Layer

The Application Layer consists of the two entities FMS (Fieldbus Message Specification) and LLI (Lower Layer Interface).

1.2.3.1 Fieldbus Message Specification (FMS)

The FMS describes communication objects, services and associated models from the point of view of the communication partner (server behaviour).

The purpose of communication at the field and process levels is to transfer data (such reading/writing of measured values, loading/starting/stopping of programs, processing of events, etc.) between two communicating stations.

For communication between an application process of one device and that of another, the process objects transferred must be made known to the communication system, which means the process objects must be listed as communication objects in an Object Dictionary (OD) (comparable to a public telephone directory). Thus, an application process must make its objects visible and available, before these can be addressed and processed by the communication services. The application processes communicating with one another on different devices, however, need more information than the acknowledgement of the communication objects for efficient communication.

Usually, the stations are located at a distance from one another, or are not accessible during operation; so they must be uniquely identified with their features in the network. Data such as vendor name, model name and profile need to be read via the bus. Moreover, information on the communication interface status of the device and on the real device (e.g., indication of servicing dates) are a very important aspects.

A public Object Dictionary provided by all stations connected to the bus, standardized device features, identical services and uniform interfaces make up the basis for open communication between devices of different vendors. This consistent view of a device is called a Virtual Field Device (VFD).

The specification describes the effect of the services on the communication objects of an application process only for Virtual Field Devices. The mapping of Virtual Field Devices to real field devices and vice versa is not subject to the specification. Between the Application Layer and the real application process lies the so-called Application Layer Interface (ALI).

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The services of the Application Layer can be accessed via this intermediate interface. It provides additional communication functions adapted to the application process. In addition, the Application Layer Interface does the mapping of the Virtual Field Device on to the real field device.

1.2.3.2 Lower Layer Interface (LLI)

Logical relationships exist between application processes with the specific purpose of transferring data. In the case, all communication relationships must be defined before a data transfer is started. These definitions are listed in layer†7 in the Communication Relationship List (CRL).

The manifold characteristics of the specification require a particular adaptation between FDL and FMS/FMA7. This adaptation is achieved by means of the LLI. The LLI is an entity of Layer 7.

The main tasks of LLI are:

-mapping of FMS and FMA7 services on to the FDL services

-connection establishment and release

-supervision of the connection

-flow control

1.2.4 User specifications

To manage peripheral devices connected through a serial interface to e. g. a controller in manufacturing application, this specification defines extented definitions to fulfil the special requirements in the area of remote peripherals.

Decentralized Peripherals (DP) are mainly used to connect automation systems (such as programmable controllers) via a fast serial link to input-/output- devices, sensors, actuators and to smart devices.

The main purpose of DP is the fast cyclic exchange of data between a powerful Master and several simple Slaves (peripheral devices). Thus, this system uses mainly the Master-Slave-type of communication services.

The hybrid media access allows Master-Slave communication as well as Master-Mas- ter communication, which is used for Data transfer between DP-Master (class 1) and DP-Master (class 2) for programmer/diagnostic-panels.

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