Siemens SIPROTEC 7SJ62 Manual page 439

System Interface
When a serial interface of the device is connected to a control center, the data connection must be checked. A
visual check of the assignment of the transmit and receive channels is important. With RS232 and fiber optic
interfaces, each connection is dedicated to one transmission direction. For that reason the data output of one
device must be connected to the data input of the other device and vice versa.
With data cables, the connections are designated according to DIN 66020 and ISO 2110:
• TxD = Data output
• RxD = Data input
• RTS = Request to send
• CTS = Clear to send
• GND = Signal/Chassis Ground
The cable shield is to be grounded at both ends. For extremely EMC-prone environments, the GND may be
connected via a separate individually shielded wire pair to improve immunity to interference.
Table 3-31 Connector Assignment at the Various Interfaces
Pin- RS232 RS485
Nr.
1 Shield (with shield ends electrically connected)
2 RxD –
3 TxD A/A' (RxD/TxD-N)
4 – –
5 GND C/C' (GND)
6 – –
1)
7 RTS –
8 CTS B/B' (RxD/TxD-P)
9 – –
1)
Pin 7 also carries the RTS signal with RS232 level when operated as RS485 interface. Pin 7 must therefore not be con-
nected!
Additional Interface (only 7SJ64)
The additional port (Port D), which is only available for device 7SJ64, is used to connect signals from one or
two RTD boxes. The connection according to one of the connection examples given in Appendix A.3 must be
verified. For the assignment of the connectors, see the table above.
Termination
The RS485 interface is bus-capable for half-duplex operation with the signals A/A' and B/B' and the common
reference potential C/C' (GND). Verify that only at the bus of the last device the terminating resistors are con-
nected but not at the bus of the other devices. The jumpers for the terminating resistors are located on the in-
terface module RS485 (see figure 3-20) or the Profibus RS485 (see figure 3-22). With 7SJ64 they are located
directly on the C–CPU-2 (see figure 3-13 and table 3-17). The terminating resistors can also be connected ex-
ternally (e.g. to the connection module, as illustrated in figure 3-14). In this case, the terminating resistors
located on the module must be disconnected.
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.
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
Profibus FMS Slave, RS485 Modbus RS485
Profibus DP Slave, RS485
–
B/B' (RxD/TxD-P)
CNTR-A (TTL)
C/C' (GND)
+5 V (max. load <100 mA)
–
A/A' (RxD/TxD-N)
–
Mounting and Commissioning
EN 100
electr.
DNP 3.0 RS485
RJ45
Tx+
– Tx–
A Rx+
RTS (TTL Pegel) –
GND1 –
VCC1 Rx–
– –
B –
– not privided
3.2 Checking Connections
IEC 60870–5–103
redundant
RS485 (RJ45)
B/B' (RxD/TxD-P)
A/A' (RxD/TxD-N)
439