Technical data

PROFIBUS networks
1.2 Basics of the PROFIBUS network
PROFIBUS Network Manual
System Manual, Edition 04/2009, C79000-G8976-C124-03
17
1.2.4 Protocols for PROFIBUS
Potential applications for PROFIBUS DP
PROFIBUS DP (distributed I/O) is used for controlling sensors and actuators using a central
controller in production engineering. Here, particular emphasis is on the many standard
diagnostics options. Other potential uses include the connection of "distributed intelligence",
in other words the internetworking of several controllers (similar to PROFIBUS FMS). Data
rates of up to 12 Mbps are possible on twisted-pair cables and/or fiber-optic cables.
Since there is no difference at layer 2 for PROFIBUS protocols, all protocols can be operated
side-by-side in a PROFIBUS network.
Potential applications of PROFIBUS PA
PROFIBUS PA (process automation) is used for the control of measuring devices by a
process control system in process engineering. This version of PROFIBUS is suitable for
hazardous areas (Ex zones 0 and 1). Here, only a weak current flows through an intrinsically
safe circuit in the bus cables, so that sparks capable of causing an explosion are not
produced even if a fault occurs. The maximum data transmission rate is 31.25 kbps.
Position in the ISO-OSI reference model
Layer
S7 protocol
Ind. Ethernet
S7 protocol
PROFIBUS
TCP
1
7
6
5
4
3
2
RFC 1006
UDP
ISO
IP
IEC
1158 -2
PADP
FDL
FMS
MPI
Figure 1-3 ISO-OSI reference model
Layer 2 in PROFIBUS is known as the FDL layer (Fieldbus Data Link).
Above layer 2, there is a specific interface that can be assigned to layer 4.
The other layers of the OSI reference model are not implemented.
The frame formats of PROFIBUS layer 2 allow considerable transmission reliability for FDL
communication (Hamming distance HD=4). Frames in which errors are detected are
repeated automatically.