Siemens SIMATIC NET PROFIBUS - Manual (Page 25)

PROFIBUS NETWORKS
1-15
PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000
1.2.7 Transmission Technique for PROFIBUS-PA
IEC 61158-2 Standard
The transmission technique corresponds to the IEC 61158-2 standard (identical
with EN 61158-2).
The transmission medium is a shielded, twisted pair cable. The signal is
transmitted as a synchronous data stream Manchester-coded at 31.25 Kbps. In
general, the data line is normally also used to supply power to the field devices.
Advantages:
S
Simple cabling with twisted pair
S
Remote power supply via the signal cores
S Intrinsically safe operation possible (for hazardous areas)
S
Bus and tree topology
S
Up to 32 nodes per cable segment
Restrictions:
S
Transmission rate restricted to 31.25 Kbps
Characteristics of the IEC 61158-2 Transmission Technique
The main characteristics of the IEC 61158-2 transmission technique are as follows:
Network topology: Bus, star and tree topology
Medium: Shielded, twisted pair cable
Achievable segment lengths: 1900 m
Transmission rate: 31.25 Kbps
Number of nodes: Maximum 127 per network