Design Guide
Revision 1.12
1998-08-12
HMS F
IELDBUS
S
YSTEMS
AB
Page 6 (35)
1 Introduction
This Design Guide is intended to provide details necessary to implement the ANYBUS DATATRANSFER
in a product.
The ANYBUS modules constitute HMS Fieldbus Systems AB’s adaptable system, which follows the official
standard for each fieldbus interface.
1.1 Terminology
Throughout this document the term "user" refers to the person or persons who are developing a fieldbus
product based on the ANYBUS DATATRANSFER module. The end-user of the product is referred to as the
"customer".
As in all communication systems the terms "read" and "write" can be ambiguous, because their meaning
depends on which end of the link is being referenced. The convention in this document is that "read" and
"write" are always being referenced to the master end of the link.
1.2 Background
The development and increasing use of intelligent field devices in the 1980s led to the need to replace the 4-
20 mA current loop standard with an open, vendor-independent, multi-drop, bi-directional digital
communication system, commonly known as fieldbus. There was also a growing need to integrate the
various microprocessor-based intelligent field devices so that users can take full advantage of a field
network. The fieldbus is a digital communication link between control systems and attached digital
devices. It has emerged to revolutionise the control environment and device characteristic in both process
and manufacturing industries.
Fieldbus protocols are based on ISO Reference Model for Open System Interconnection (OSI-RM), ISO 7498.
However, fieldbuses commonly use only layer 1, 2, 7 of OSI-RM, layer 3 through 6 are bypassed for real-
time purpose. There is also a new User Layer added on top of the Application Layer, where distributed
control strategy is implemented and which makes fieldbuses much more than a communication network.
There are a wide range of competing bus systems on the market, which mainly focus on part of the overall
system. These facts make it hard for both the user and the customer to choose which fieldbus they should
use. The solution is the ANYBUS concept. The ANYBUS modules make it possible for the manufacturer to
provide any fieldbus system to their products, that is supported by the ANYBUS.
1.3 Conditions of Trademark Use
Please see document: ABTM-01.
