Omron C200HW-PRM21 Operation Manuals page 19

Protocol architecture
Layer 1, 2 and user interface
Transmission medium
High-speed, inexpensive
Easy installation
Cable length
User Interface Layer
(7) Application Layer
(6) Presentation Layer
(5) Session Layer
(4) Transport Layer
(3) Network Layer
(2) Data Link Layer
(1) Physical Layer
PROFIBUS-DP uses layers 1 and 2, and the user interface. Layers 3 to 7 are
not defined. This streamlined architecture ensures fast and efficient data
transmission. The application functions which are available to the user, as
well as the system and device behaviour of the various PROFIBUS-DP device
types, are specified in the user interface. RS-485 transmission technology or
fibre optics are available for transmission. RS-485 transmission is the most
frequently used transmission technology. Its application area includes all
areas in which high transmission speed and simple inexpensive installation
are required. Twisted pair shielded copper cable with one conductor pair is
used.
The RS-485 transmission technology is very easy to handle. Installation of the
twisted pair cable does not require expert knowledge. The bus structure
permits addition and removal of stations or step-by-step commissioning of the
system without influencing the other stations. Later expansions have no effect
on stations which are already in operation.
Transmission speeds between 9.6 kbit/s and 12 Mbit/s can be selected. One
unique transmission speed is selected for all devices on the bus when the
system is commissioned.
The maximum cable length depends on the transmission speed (see table
below). The specified cable lengths are based on type-A cable
section 2-3-1). The length can be increased by the use of repeaters. The use
of more than 3 repeaters in series is not recommended.
Baud rate (kbit/s)
9.6
19.2
93.75
187.5
500
1500
3000
6000
12000
DP-Profiles
DP-Extensions
DP Basic Functions
NOT DEFINED
Fieldbus Data Link (FDL)
RS-485 / Fibre Optics
Distance/segment (m)
1200
1200
1200
1000
400
200
100
100
100
Section 1-2
(see
3