Technical data

2.2.3 Transmission Techniques
With SINEC L2/L2FO there are two different transmission techniques
available (RS-485, FO) for two different transmission media (twisted pair or
fiber-optic cable). The SINEC L2/L2FO communications processors (CPs)
generally support both transmission techniques (refer to the manuals for the
specific CPs). The transmission technique is selected along with the SINEC
L2/L2FO bus terminal type.
2.2.3.1 Transmission According to RS-485
The transmission technique RS-485 corresponds to symmetrical data
transmission with NRZ coding according to the USA standard EIA RS-485
/4/. The PROFIBUS standard DIN 19245 Part 1 stipulates RS-485 as
transmission technique version 1 on a twisted pair transmission medium.
The maximum length of a bus segment depends on the data rate and the
cable used.
RS-485 has the following electrical characteristics:
Topology bus, terminated at both ends by its characteristic im-
pedance; connecting cables to SINEC L2 station
max. 3 m.
Medium: shielded, twisted pair
characteristic impedance: 160
Ω
loop impedance: 110
Ω
operating capacitance: 30 nF/km
attenuation: 0.9 dB/100 m (200 kHz)
wire cross section: 0.34 mm
2
Data rate (dr): 9.6 / 19.2 / 93.75 / 187.5 / 500 / 1,500 Kbps
Cable length
(per bus segment):
1,200 m for dr <= 93.75 Kbps
1,000 m for dr = 187.5 Kbps
400 m for dr = 500.0 Kbps
200 m for dr = 1,500.0 Kbps
System Overview B8976060/02
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