Overview Of Profibus; Introduction; Profibus Communication Protocol - Omron PROFIBUS DP GATEWAY Operation Manual

Overview of PROFIBUS

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Overview of PROFIBUS

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Introduction

Standard EN50170
PROFIBUS FMS
PROFIBUS DP
PROFIBUS PA
Uniform Bus Access
Protocol
! C a u t i o n
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PROFIBUS Communication Protocol

OSI reference model
ISO-7498
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PROFIBUS (PROcess FIeldBUS) is an open fieldbus standard for a wide
range of applications in manufacturing, processing and building automation.
The Standard, EN 50170 (the Euronorm for field communications), to which
PROFIBUS adheres, guarantees vendor independence and transparency of
operation. It enables devices of various manufacturers to intercommunicate
without having to make any special interface adaptations.
The PROFIBUS family comprises three mutually compatible versions:
PROFIBUS FMS, PROFIBUS DP and PROFIBUS PA.
FMS means Fieldbus Message Specification. This version is the general-pur-
pose solution for high-level extensive and complex communication tasks.
Powerful services open up a wide range of applications and provide great
flexibility.
DP means Decentralized Periphery. PROFIBUS DP is optimized for high
speed and low-cost interfacing. It is specially designed for communication
between automation control systems and distributed I/O at the device level.
PA means Process Automation. It permits sensors and actuators to be con-
nected to one common bus even in areas where intrinsically safe products are
required. It also permits data and power to be supplied over the bus using
2-wire technology according the international standard IEC 1158-2.
PROFIBUS DP and PROFIBUS FMS use the same transmission technology
and uniform bus access protocol. Consequently, both versions can be oper-
ated simultaneously on the same bus. FMS field devices, however, cannot be
controlled by DP masters and vice versa.
It is not possible to exchange one of these family members by another family
member. This will cause faulty operation.
The rest of this section describes the PROFIBUS DP Protocol architecture.
In general, the PROFIBUS communication protocol is based on the Open
System Interconnection (OSI) reference model in accordance with the inter-
national standard ISO-7498 (see the following illustration). The model defines
7 layers of communication functions, three of which - layers 1, 2, and 7 - are
used in PROFIBUS.
• Layer 1, the Physical Layer of this model, defines the physical transmis-
sion characteristics.
• Layer 2, the Data Link Layer of this model, defines the bus access proto-
col. This protocol also includes data security and the handling of trans-
mission protocols and telegrams.
• Layer 7, the Application Layer of this model, defines the application func-
tions. This Layer is only applicable to PROFIBUS FMS.
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