PROFIBUS DP Network Characteristics
Overview
The LTMR PROFIBUS DP controller complies with the PROFIBUS DP standard specification.
The PROFIBUS Installation Guideline for Design and PROFIBUS Installation Guideline for Cabling and Assembly, published on www.profibus.com/downloads/, define the characteristics of the Modbus protocol.
PROFIBUS DP Network Standard Diagram
The diagram below corresponds to the PROFIBUS DP standard specification.
Characteristics for Connection to the PROFIBUS DP RS 485 Bus
The RS 485 standard allows variants of some characteristics:
-
Polarization
-
Line terminator
-
Number of secondaries
-
Bus length
|
Characteristics |
Value |
|---|---|
|
Topology |
Linear bus with line terminations |
|
Transmission Mode |
Half duplex |
|
Transmission Rate |
From (in kBaud):
Up to (in MBaud):
|
|
Possible Transmission Media |
Twisted-pair line (standard version, type RS 485) |
|
Maximum number of secondaries connected to one primary |
128 (0, 126, and 127 are reserved) |
|
Maximum number of secondaries per derivation |
32 |
|
Maximum number of repeaters per bus |
Nine repeaters maximum including five repeaters maximum cascaded in one derivation |
|
Line terminator |
Active termination |
Use of Repeaters
A PROFIBUS DP network bus can be segmented with repeaters for many reasons:
-
Maximum length of the sum of derivations reached
-
Need to connect more than 32 secondary communicating devices on the bus
-
Need to isolate the derivation
-
Need for derivation
-
Need for removable connection to equipment
For more information about the topology with a repeater, refer to the PROFIBUS Installation Guideline for Design .
Maximum Bus Cable Length
The bus cable lengths and corresponding baud rates are as follows:
|
Maximum Bus Cable Length per Segment |
Maximum Bus Cable Length with Three Repeaters |
Baud Rates |
|---|---|---|
|
1,200 m (3,936 ft) |
4,800 m (15,748 ft) |
9.6 / 19.2 / 45.45 / 93.75 kBaud |
|
1,000 m (3,280 ft) |
4,000 m (13,123 ft) |
187.5 kBaud |
|
500 m (1,640 ft) |
2,000 m (6,561 ft) |
500 kBaud |
|
200 m (656 ft) |
800 m (2,624 ft) |
1.5 MBaud |
|
100 m (328 ft) |
400 m (1,312 ft) |
3 / 6 / 12 MBaud |