Siemens siprotec 7SA522 User Manual page 477

RS 485
Termination
Time
Synchronization
Interface
Optical Fibres
7SA522 Manual
C53000-G1176-C119-2
The RS485 interface is capable of half-duplex service with the signals A/A' and B/B'
with a common relative potential C/C' (DGND). Verify that only the last device on the
bus has the terminating resistors connected, and that the other devices on the bus do
not. The jumpers for the terminating resistors are on the interface module RS 485
(Figure 8-11) or on the Profibus module (Figure 8-12).
If the bus is extended, make sure again that only the last device on the bus has the
terminating resistors switched in, and that all other devices on the bus do not.
Either 5 VDC, 12 VDC or 24 VDC time synchronization signals can be processed if the
connections are made as indicated in Table 8-9.
Table 8-9 Pin-assignments for the D-subminiature port of the
interface
Pin-No. Designation
1 P24_TSIG
2 P5_TSIG
3 M_TSIG
4 M_TSYNC*)
5 Screen
6 –
7 P12_TSIG
8 P_TSYNC*)
9 Screen
*) occupied, but must not be connected
Signals transmitted over optical fibres are unaffected by interference. The fibres guar-
antee electrical isolation between the connections. Transmit and receive connections
are identified with the symbols
The character idle state for the optical fibre interface is "Light off." If this setting is to
be changed, use the operating program DIGSI
Installation and Commissioning
time synchronization
Signal meaning
Input 24 V
Input 5 V
Return Line
Return Line*)
Shield potential
–
Input 12 V
Input 24 V*)
Shield potential
for transmit and
®
4, as described in Section 5.5.
for receive.
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