Bus TerminationΒΆ
The line ends of the bus segment must be equipped with bus termination resistors. Normally, these resistors are integrated in the interface connectors.
Note
The earthing of the shield should take place at the switch-gear cabinet, see System-Data AC500 System Data AC500.
Mounting on Terminal Units TU517 or TU518:
The assignment of the terminals 1.0 - 1.9:
| Terminal | Signal | Description |
|---|---|---|
| 1.0 | B | Data line B (receive and send line, positive) |
| 1.1 | B | Data line B (receive and send line, positive) |
| 1.2 | A | Data line A (receive and send line, negative) |
| 1.3 | A | Data line A (receive and send line, negative) |
| 1.4 | TermB | Bus termination data line B |
| 1.5 | TermB | Bus termination data line B |
| 1.6 | TermA | Bus termination data line A |
| 1.7 | TermA | Bus termination data line A |
| 1.8 | DGND | Reference potential for data transmission |
| 1.9 | DGND | Reference potential for data transmission |
At the line ends of a bus segment, termination resistors must be connected. If using TU517/TU518, the bus termination resistors can be enabled by connecting the terminals TermA and TermB to the data lines A and B (no external termination resistors are required, see illustration below).
Note
If using TU517/TU518, note that the termination resistors are not located inside the TU, but inside the Bus Module CI541-DP. I. e. when removing the device from the TU, the bus termination resistors are not connected to the bus any more. The bus itself will not be disconnected if a device is removed.
If using TU517/TU518 the max. permitted baud rate is limited to 1,5 MBaud.