Specifications For Rs485 Cable; Connector Pin Assignments - Siemens SIMATIC S7 System Manual

Communication
8.6 RS485
8.6.5.4

Specifications for RS485 cable

S7-200 SMART CPU networks use the RS485 standard on twisted pair cables. The following
table lists the specifications for the network cable. You can connect up to 32 devices on a
network segment.
Specifications
Cable type
Loop resistance
Effective capacitance
Nominal impedance
Attenuation
Cross-sectional core area
Cable diameter
8.6.5.5

Connector pin assignments

The RS485 communication port on the S7-200 SMART CPUs is RS485-compatible on a
nine-pin subminiature D connector, in accordance with the PROFIBUS standard as defined
in the European Standard EN 50170. The following table shows the connector that provides
the physical connection for the communication port and describes the communication port
pin assignments.
Table 8- 17
Pin number
1
2
3
4
5
6
7
8
9
Connector
shell
The CPU utilizes pin 9 of the RS485 connector to detect when a USB-PPI cable is connected. The
1
check for USB-PPI cables is only done on the CRs models. The ST and SR models ignore the
state of pin 9. Ensure that any cables used for Freeport do not connect to pin 9 for the CRs mod-
els.
460
Pin assignments for the S7-200 SMART CPU integrated RS485 port (Port 0)
Connector
Description
Shielded, twisted pair
≤115 /km
30 pF/m
Approximately 135 to 160
(frequency = 3MHz to 20 MHz)
0.9 dB/100 m (frequency=200 kHz)
0.3 mm to 0.5 mm
2 2
8 mm +0.5 mm
Signal Integrated RS485 port (Port 0)
Shield Chassis ground
24 V Return Logic common
RS485 Signal B RS485 Signal B
Request-to-Send RTS (TTL)
5 V Return Logic common
+5 V +5 V output, 100 Ω series resistor
+24 V +24 V output
RS485 Signal A RS485 Signal A
Not applicable Programmer detection (input)
Shield Chassis ground
System Manual, V2.3, 07/2017, A5E03822230-AF
1
S7-200 SMART