Attachment plug for the bus cable
9-pin D-sub connector, male
|
Parameter |
Value |
|---|---|
|
Fastening torque |
0.4 Nm |
Assignment
|
Pin |
Signal |
Description |
|---|---|---|
|
1 |
Shield |
Shielding, protective ground |
|
2 |
not used |
- |
|
3 |
RxD/TxD-P |
Reception / transmission line, positive |
|
4 |
CBTR-P |
Control signal for repeater, positive (optional) |
|
5 |
DGND |
Reference potential for data lines and +5 V |
|
6 |
VP |
+5 V, supply voltage for bus terminating resistors |
|
7 |
not used |
- |
|
8 |
RxD/TxD-N |
Reception / transmission line, negative |
|
9 |
CNTR-N |
Control signal for repeater, negative (optional) |
Bus cable
|
Parameter |
Value |
|---|---|
|
Type |
Twisted pair (shielded) |
|
Characteristic impedance |
135 Ω ... 165 Ω |
|
Cable capacitance |
< 30 pF/m |
|
Conductor diameter of the cores |
≥ 0.64 mm |
|
Conductor cross section of the cores |
≥ 0.34 mm² |
|
Cable resistance per core |
≤ 55 Ω/km |
|
Loop resistance (resistance of two cores) |
≤ 110 Ω/km |
Cable lengths
The maximum possible cable length of a PROFIBUS subnet within a segment depends on the tranmission rate (baud rate).
|
Transmission Rate |
Maximum Cable Length |
|---|---|
|
9.6 / 19.2 / 93.75 kBaud |
1200 m |
|
187.5 kBaud |
1000 m |
|
500 kBaud |
400 m |
|
1.5 MBaud |
200 m |
|
3 MBaud to 12 MBaud |
100 m |
Branch lines are generally permissible for transmission rates of up to 1500 kbit/s. But in fact they should be avoided for transmission rates higher than 500 kbit/s.
Bus terminating resistors
The line ends (of the bus segments) have to be terminated using bus terminating resistors according to the drawing below. The bus terminating resistors are usually placed inside the bus connector.
Repeaters
One bus segment can have up to 32 subscribers. Using repeaters a system can be expanded to up to 126 subscribers. Repeaters are also required for longer transfer lines. Please note that a repeater's load to the bus segment is the same as the load of a normal bus subscriber. The sum of normal bus subscribers and repeaters in one bus segment must not exceed 32.
