Product manual

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PC/VMECNC
Host
DCS
Temp
Controller
I/O
Field
Device
Motor
Drives
Trans-
mitter
Field
Device
Factory
Level
Cell
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MMS, TCP/IP Backbone
PROFIBUS-FMS
PROFIBUS-DP
PROFIBUS-PA
PLC
PC
Figure 1 PROFIBUS Application Areas
The PROFIBUS Option supports the PROFIBUS-DP variant of the PROFIBUS protocol which
is designed especially for communication between automatic control systems and distributed I/O
at the device level. It is most often used to allow a central Programmable Logic Controller or PC
based control system to use external ‘slave’ devices for I/O or specialised functions. The
principal advantage is that these devices may be distributed around a machine, thereby saving on
the cost of point to point wiring. The ‘open’ nature of the network also permits equipment from
different manufacturers to be mixed on the same bus. Additionally, the off-loading of complex
and specialised tasks such as PID temperature control lessens the processing load on the central
PLC so that its other functions may be carried out more efficiently and require less CPU
memory.
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PROFIBUS is a vendor independent, open fieldbus standard for a wide range of applications in
manufacturing, process and building automation. Vendor independence and openness are
guaranteed by the PROFIBUS standard EN50170. With PROFIBUS, devices from different
manufacturers can inter-communicate. Suitable interfaces exist for PLCs, which include the
Siemens, Mitsubishi and Allen Bradley range.
PROFIBUS-DP (De-central Periphery) is described in DIN 19245 Part 3, and forms part of EN
50170 with P-Net and WorldFIP. However it is important to note that P-Net and WorldFIP are
wholly incompatible with PROFIBUS, using different wiring and transmission technologies.
The PROFIBUS-DP network uses a high speed version of the RS485 standard, permitting baud
rates of up to 12Mbaud. A table of network speed against segment length is given in Chapter 3.
A maximum of 32 PROFIBUS-DP stations (nodes) may be contained within a single network
segment. Use of RS485 repeaters allows a total of up to 126 stations.
PROFIBUS-DP is a multimaster, master-slave, token passing network. More detailed
information, including a detailed guide to products available, may be obtained from the various
world-wide PROFIBUS user organisations. You will find contact information in trade magazines
or by reference to http://www.profibus.com on the World Wide Web.
PROFIBUS is available in two other types, aimed at different application areas, as follows:
1. PROFIBUS-PA is designed especially for process automation. It permits sensors and
actuators to be connected on one common bus line even in intrinsically safe areas.
PROFIBUS PA permits data communication and power over the bus, using intrinsically safe,
2-wire technology according to the international standard IEC 1158-2, but may also be used
on the standard RS485 cabling for non-intrinsically safe applications.
2. PROFIBUS-FMS is the general purpose solution for communication tasks at the cell level.