ABB AC 800M

Section 2 Transmission Technology MBP (IEC 61158-2) Transmission Technology
3BDS009029R5001 B 33
More information about this technology is given in the guidelines and specification
from the PROFIBUS International organization
(http://www.profibus.com).
MBP (IEC 61158-2) Transmission Technology
The MBP transmission technology (Manchester Coded, Bus Powered), which is the
new naming for the previous designation “IEC 61158-2 Physics”, is mostly used for
applications in the process automation with a requirement for bus powering and
intrinsic safety of devices. The reason for this name change is that, in its definitive
version, the IEC 61158-2 describes several different connection technologies,
including MBP technology, not being therefore unambiguous. Compared to the
previously used procedure RS485-IS, the Fieldbus Intrinsically Safe Concept
(FISCO), which was specially developed for interconnection of intrinsically safe
field devices, considerably simplifies planning and installation.
MBP cable type and speed
MBP is synchronous transmission with a fixed transmission rate of 31.25 Kbit/s and
Manchester coding. This allows installation of PROFIBUS networks also in
potentially explosive areas and be intrinsically safe. The intrinsically safe
transmission technology MBP is usually limited to a specific segment (field devices
in hazardous areas) of a plant, which is then to the RS485 bus line via PROFIBUS
DP/PA Linking Device.
Tree or line structures as well as any combination of the two are supported by
PROFIBUS with MBP transmission. The transmission medium for MBP is a
shielded two-wire cable, normally covered by an black color cable sheath for non
intrinsically safe areas and blue color for hazardous areas. The maximum
permissible spur line lengths must be taken into account when calculating the
overall PROFIBUS line length. In intrinsically safe applications a spur line has a
maximum permissible length of 30m.