Siemens SIMATIC NET PROFIBUS, Owner'S Manual

Page: 126 / 490

Passive Components for RS-485 Networks
4-28
PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000
Disconnect Function
The disconnect function means that the remaining LAN cable is disconnected from
the bus when the terminating resistor is activated. If the terminating resistor is
accidentally activated in the middle of the LAN cable, the error can be recognized
and localized immediately due to the nodes that are no longer accessible.
Disconnecting a Station
The bus connector allows you to disconnect a node from the bus without
interrupting the data traffic on the bus.
Removing the bus connector when the terminating resistor is activated at the end
of the cable causes disruptions on the bus and is not permitted.
Bus Connector with PG Socket
We recommend that you include at least one bus connector with a PG socket in
each bus segment. This makes it easier to commission using a programming
device or PC.
In the bus connectors with a PG socket, all the contacts are connected 1:1 with the
connector pins; in other words, the pinout is the same as the pinout of the attached
device.
Pinout of the Sub-D Male Connector
Table 4-5 shows the pinout of the 9-pin sub-D male connector.
Table 4-5 Pinout of the 9-pin Sub-D Male Connector
Pin
no. Signal
name
Meaning
1 - -
2 - -
3 RxD/TxD-P Data line B
4 – –
5 M5V2 Data reference potential (from node)
6 P5V2 Power supply plus (from node)
7 - -
8 RxD/TxD-N Data line A
9 - -