Cable Length¶
The maximum possible cable length of a PROFIBUS subnet within a segment depends on the baud rate (transmission rate).
| Baud rate | Maximum cable length |
| 9.6 kBaud to 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 |
The assignment of the other terminals:
| Terminal | Signal | Description |
|---|---|---|
| 2.0 | AI0+ | Plus pole of analog input signal 0 |
| 2.1 | AI1+ | Plus pole of analog input signal 1 |
| 2.2 | AI2+ | Plus pole of analog input signal 2 |
| 2.3 | AI3+ | Plus pole of analog input signal 3 |
| 2.4 | AI- | Minus pole of analog input signals 0 to 3 |
| 2.5 | AO0+ | Plus pole of analog output signal 0 |
| 2.6 | AO1+ | Plus pole of analog output signal 1 |
| 2.7 | AI- | Minus pole of analog output signals 0 and 1 |
| 2.8 | UP | Process voltage UP (24 VDC) |
| 2.9 | ZP | Process voltage ZP (0 VDC) |
| 3.0 | DI0 | Signal of the digital input DI0 |
| 3.1 | DI1 | Signal of the digital input DI1 |
| 3.2 | DI2 | Signal of the digital input DI2 |
| 3.3 | DI3 | Signal of the digital input DI3 |
| 3.4 | DI4 | Signal of the digital input DI4 |
| 3.5 | DI5 | Signal of the digital input DI5 |
| 3.6 | DI6 | Signal of the digital input DI6 |
| 3.7 | DI7 | Signal of the digital input DI7 |
| 3.8 | UP | Process voltage UP (24 VDC) |
| 3.9 | ZP | Process voltage ZP (0 VDC) |
| 4.0 | DO0 | Signal of the digital output DO0 |
| 4.1 | DO1 | Signal of the digital output DO1 |
| 4.2 | DO2 | Signal of the digital output DO2 |
| 4.3 | DO3 | Signal of the digital output DO3 |
| 4.4 | DO4 | Signal of the digital output DO4 |
| 4.5 | DO5 | Signal of the digital output DO5 |
| 4.6 | DO6 | Signal of the digital output DO6 |
| 4.7 | DO7 | Signal of the digital output DO7 |
| 4.8 | UP3 | Process voltage UP3 (24 VDC) |
| 4.9 | ZP | Process voltage ZP (0 VDC) |
Warning
:strong:Removal/Insertion under power
The devices are not designed for removal or insertion under power. Because of unforeseeable consequences, it is not allowed to plug or unplug devices with the power being ON.
Make sure that all voltage sources (supply and process voltage) are switched off before you
- connect or disconnect any signal or terminal block
- remove, mount or replace a module.
Disconnecting any powered devices while energized in a hazardous location could result in an electric arc, which could create a flammable ignition resulting in fire or explosion.
Make sure that power is removed and that the area has been thoroughly checked to ensure that flammable materials are not present prior to proceeding.
The devices must not be opened when in operation. The same applies to the network interfaces.
Attention
:strong:Risk of damaging the PLC modules!
Overvoltages and short circuits might damage the PLC modules.
- Make sure that all voltage sources (supply and process voltage) are switched off before you begin with operations at the system.
- Never connect any voltages or signals to reserved terminals (marked with —). Reserved terminals may carry internal voltages.
Note
For the open-circuit detection (cut wire), each channel is pulled up to “plus” by a high-resistance resistor. If nothing is connected, the maximum voltage will be read in then.
Note
Analog signals are always laid in shielded cables. The cable shields are earthed at both ends of the cables. In order to avoid unacceptable potential differences between different parts of the installation, low resistance equipotential bonding conductors must be laid.
For simple applications (low electromagnetic disturbances, no high requirement on precision), the shielding can also be omitted.
The following figures show the electrical connection of the PROFIBUS DP Bus Module CI541-DP.
Further information is provided in the System Technology chapter PROFIBUS: PROFIBUS DP Communication Modules