Technical data

58 Theoretical and general applications www.westermo.com
PROFIBUS
PROFIBUS is an open uniform digital communication system for a broad range of
applications, especially within engineering and process automation. PROFIBUS is ideal
for both fast time critical applications and for complex communication applications.
PROFIBUS communication is rooted in the international standards IEC 61158 and IEC
61784 and with that satisfies the requirements of fieldbus users of being open and
manufacturer independent. Communication between products from different manu-
facturers can take place without adaptation or specialised software.
History
The history of PROFIBUS goes back to 1987 when a European group consisting of
companies and institutions established a strategy for a fieldbus. The group was made
up of 21 members, companies, universities, other institutions and different authorities.
The aim was to realise and receive general recognition for a serial fieldbus. An impor-
tant intermediate target was to standardise an interface for the field devices. With the
intention of reaching a wide standard, the concerned members of ZVEI (Central
Association for the Electrical Industry) agreed to support a common technical concept
for engineering and process automation. The first step was the specification of the
complex communication protocol PROFIBUS FMS (Fieldbus Message Specification),
which was drawn up to handle very demanding communication applications. An addi-
tional step was taken in 1993 when the first specification was completed for the sim-
pler and with that significantly faster Profibus DP protocol, DP stands for Decentralized
Peripherals. This protocol has under gone continuous development and is now avail-
able in three versions offering different degrees of functionality: DP-V0, DP-V1 and
DP-V2. Over and above DP there is also PROFIBUS PA (Process Automation), which
has been developed for the specific requirements of the process industry. Motion
Control is a version for drive equipment and PROFIsafe is a version for safety applica-
tions. We will only describe DP related applications in the manual.
PROFIBUS communication
Profibus is based on RS-485 probably the most common industrial transmission tech-
nique. It uses a screened, twisted pair cable and can support transmission rates of up
to 12 Mbit/s. The version RS-485-IS has now recently been specified as a 4-wire trans-
mission media for protection class E for use in explosive environments.
The transmission technique MBP (Manchester coded, Bus Powered) is used for appli-
cations in process automation that require a power supply across the bus to units in
intrinsic safety areas. Transfer of PROFIBUS data over fibre optic cable is recommend-
Data Max
rate segment lenght
(kbit/s) (m)
9.6 1200 (0.75 mi)
19.2 1200 (0.75 mi)
45.45 1200 (0.75 mi)
93.75 1200 (0.75 mi)
187.5 1000 (0.62 mi)
500 400 (1312 ft)
1500 200 (656 ft)
3000 100 (328 ft)
6000 100 (328 ft)
12000 100 (328 ft)
The values refer to cable type A
with caracteristic as follow:
Surge Impedance 135 – 165 Ω
Capacitance <30 pf/m
Loop resistance 110 Ω/km
Core diameter 0.64 mm
Cable area >0.34 mm
2
B A C K