are new to the Fieldbus Industry, then this page
is for you. Here, we will discuss what Fieldbuses
are and why then are used. Also, other topics
such has what constitutes are Fieldbus and what
Fieldbuses are currently on the market will be
discusses. If you have any questions, please
don't hesitate to contact. We will always be
available to answer any questions you may have.
Fieldbuses are communication
technologies and products used in automation and process
control industries. We will distinguish between proprietary
fieldbuses and open fieldbuses.
are an intellectual property of a particular company or
body. To use a Proprietary, a license is required,
however this may only give you partial rights. Such
licenses are usually only granted at the discretion of
the owner or owners and are generally very expensive.
Open Fieldbuses however
are the opposite. For a Fieldbus to be Open, it must
satisfy the following criteria.
- The full Fieldbus
Specification must be published and available at
a reasonable price.
- Critical ASIC
components must be available, also at a
- Well defined
validation process, open to all of the Fieldbus
A Fieldbus may allow for
Devices from different
manufactures can be safely connected to the same
The ability to connect
successfully, elements from different suppliers.
Devices from one
manufacture can be replaced with functionally
equivalent devices from another manufacture.
Interconnectivity is the
minimum common denominator and does not offer any
significant benefits by itself. If interoperability
cannot be achieved, the Fieldbus installation exercise is
worthless and the particular Fieldbus is useless. The
ultimate goal is interchangeability. It can only be
achieved if the Fieldbus specifications are complete and
a proper system testing and validation process is
Why Use Fieldbuses
Fieldbuses, if correctly selected to
suit the application offer the user many advantages both
tangible and intangible. A list of these advantages follows.
- Reduces the complexity
of the control system in terms of hardware outlay.
There is a reduction in the amount of PLC or DCS
hardware requirements. This reduces the need for
large control cabinets to house such equipment and
associated connecting hardware. As cabling is
reduced, the need for junction boxes, control panels
and large cabling runs is eliminated. These
advantages relate to a direct cost saving.
- As the hardware
requirements are reduces so are the installation
times and man power requirements. Commissioning of
new installations is far more efficient as the
diagnostic functions of Fieldbus systems identify any
- Resulting in the
reduced complexity of the control system, project
design engineering is made simpler, more efficient
and conversely less expensive. The need for designing
complicated instrument loop drawing, cable schedules,
termination schedules and wiring diagrams is to a
- Future modifications,
upgrades and refurbishment's are easily carried out
at very little expense.
- By selecting a
recognised and well established system, this will
make the Fieldbus equipment in you plant or plants
interchangeable between suppliers. The need to be
concerned about connections, compatibility and other
potential problems is eradicated.
- Downtime and production
losses are reduced due to the superior diagnostic and
fault finding procedure that fieldbuses are capable
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Constitutes a Fieldbus
The specification of a Fieldbus
should ideally cover all of the seven layers of the OSI
model. An outline of how these layers should be covered
Physical Layer 
What type of signals are
present, levels, representation of 1's and 0's, what type
of media, connects, etc.
Link Layer 
establishing links between to communicating parties.
Network Layer 
Method of selecting the
node of interest, method of routing data.
Transport Layer 
Ensuring the what was
sent arrives at the receiver correcting any correctable
Session Layer 
Not applicable to
Presentation Layer 
Not applicable to
Application Layer 
Meaning of data.
The best way of covering
layer 7 is to define standard profiles for standard devices.
For example, device parameters should be defined, the format
of these parameters and the run time data to and from the
device should also be defined.
If your Fieldbus and
associated IO devices define a standard profile, the IO
devices can be easily replaced with functionally equivalent
devices from other manufactures. For example, take a variable
speed motor driver, you can replace the motor driver you use
with any compatible motor driver with minimal problems. If no
standard profiles exist, your installation is specific and
you will have no option of using alternative components.
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What Fieldbuses Are Currently On
Below is a list of all the Fieldbuses
Fieldbus Specialists are in contact with. A range of the
listed Fieldbuses are fully defined Fieldbuses, whereas other
are basic technologies (Fieldbus primitives). A number of
Fieldbuses presented are proprietary, whereas the majority
are open. Fieldbuses and similar technologies which are not
industry specific have not been presented.
If you require any detailed
information regarding any of the listed Fieldbus, please
contact us directly. if you find any of the information
inaccurate or incomplete and wish us to correct it, please
send us an e-mail.
Technologics Fieldbuses are
||BITBUS (IEEE 1118)
Older Fieldbus Technologies
||Data Highway [+]
Established Fieldbus Systems
||Omron Sysmac Bus
||Allen-Bradley Remote IO
||Smart Distributed Systems
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