Thermcraft XST-3-0-36-3V - Manual (Page 159)

Installation and Operation Handbook Safety Information
2408 and 2404 Controller E-1
Appendix E: Profibus Communications
Introduction
The 2408f and 2404f are special versions of the 2408 and 2404 controllers designed for
Profibus-DP communications. The ‘standard’ 2408 or 2404 controllers cannot be upgraded
to a 2408f or 2404f as the latter uses a different version of the microprocessor board.
Profibus-DP is available with either the 85 to 264Vac or 20-29Vac/dc supply
Apart from the restrictions listed below, the operation, functions and wiring of the 2404f and
2404f are identical to that of the standard 2408 and 2404 controllers.
• Modbus communications may be configured to replace Profibus-DP if required.
• This must be installed in module slot H.
• EI Bisynch protocol is not supported, therefore the IPSG instrument programming
system cannot be used.
• The 20 programmer option is not available.
• The PDSIO input and output modules can only be installed in module slot J.
About Profibus-DP
Profibus-DP is an industry standard, open network used to connect simple devices in a
machine or manufacturing plant. 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. One advantage is that these devices may be distributed around a machine, saving
on the cost of point to point wiring. The ‘open’ nature of the network permits equipment
from different manufacturers to be mixed easily so that best of breed equipment may be used.
Additionally, the off-loading of 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.
Profibus-DP is described in DIN 19245 Part 3, and is part of EN 50170.
The Profibus-DP network uses a high speed version of the RS485 standard, permitting baud
rates of up to 12Mbaud. The 2408f and the 2404f support rates of up to 1.5 MBaud in order
to meet electrical isolation standards. A table of network speed against line length is given in
the section on wiring below.
Up to 32 Profibus stations (nodes) may be wired to a single network segment. Use of RS485
repeaters allows a total of up to 127 stations.
Other variants of Profibus that exist are Profibus FMS, which is designed to allow higher
level communication such as that between PLCs and SCADA systems, and Profibus PA,
which has an optional low speed, intrinsically safe, physical medium and is designed for use
in the Process Industry. The 2408f and 2404f controllers can be used on a combined DP and
FMS network, sharing the same physical medium, but may only be used for PA when the
intrinisically safe physical medium is not used.