×
Siemens Industry Online Support
Siemens AG
Entry type: FAQ Entry ID: 109736665, Entry date: 04/23/2019
(7)
Rate

How do you connect the RS485/RS422 interfaces of SIMATIC and SIPLUS modules for serial communication?

  • Entry
  • Associated product(s)
Serial communication is possible via the RS485 and RS422 interfaces with the modules below, . The terminal assignments are given in the diagrams.

Fig. 1 (RS485) and Fig. 2 (RS422)

  • ET 200SP CM PtP

Fig. 3 (RS485) and Fig. 4 (RS422)

  • S7-1500 CM PtP RS485/RS422 BA/HF
  • CP 340 / CP 341
  • CP 440 / CP 441-1 / CP 441-2

Fig. 5 (RS485) and Fig. 6 (RS422)

  • ET 200S 1SI

Fig. 7 and Fig. 8 (each RS485)

  • CM 1241
  • CB 1241

Note
If you use an RS485 connection cable or an RS422 connection cable that is longer than 50m, you should add a terminating resistor of approx. 330Ω.
Exceptions here are the modules CM 1241 and CB 1241 with other terminating resistors.
They only terminate the two ends of the RS485 network. The devices between the two terminal devices are not terminated.

ET 200SP CM PtP
Fig. 1 shows the terminal assignment for RS485 communication.
 

Fig. 1

Fig. 2 shows the terminal assignment for RS422 communication.
 

Fig. 2

 
The following overview shows you accessories for ET 200SP CM PtP.
 
Base UnitArticle numberConnecting cable cross-section
Base Unit Type A0, BU15-P16+A0+2B6ES7193-6BP00-0BA0
  • min: 0.14 mm², AWG 26 (recommended)
  • max: 2.5 mm², AWG 14
Base Unit Type A0, BU15-P16+A0+2D6ES7193-6BP00-0DA0
Base Unit Type A0, BU15-P16+A10+2B6ES7193-6BP20-0BA0
Base Unit Type A0, BU15-P16+A10+2D6ES7193-6BP20-0DA0

Table 1

S7-1500 CM PtP RS485/RS422 BA/HF, CP340, CP 341, CP 440, CP 441-1, CP 441-2
Fig. 3 shows the terminal assignment for RS485 communication.
 

Fig. 3

 
Fig. 4 shows the terminal assignment for RS422 communication.
 

Fig. 4

>The following overview shows you accessories for S7-1500 CM PtP RS485/RS422 BA/HF, CP 340, CP 341, CP 440, CP 441-1 and CP 441-2.
 

Plug-in connecting cable Article number
S7 plug-in connecting cable RS422/485, 5 m
Cable for point-to-point connections RS422-RS422, each 15-pin Sub-D male connector
6ES7902-3AB00-0AA0
S7 plug-in connecting cable RS422/485, 10 m
Cable for point-to-point connections RS422-RS422, each 15-pin Sub-D male connector
6ES7902-3AC00-0AA0
S7 plug-in connecting cable RS422/485, 50 m
Cable for point-to-point connections RS422-RS422, each 15-pin Sub-D male connector
6ES7902-3AG00-0AA0

Table 2

ET 200S 1SI
Fig. 5 shows the terminal assignment for RS485 communication.
 

Fig. 5

The following lengths are possible for the ET 200S 1SI module as communication module when using the cable type LIYCY 3 x 2& x 0.14:

  • max. 1200 m for 19200 baud
  • max. 500 m for 38400 baud
  • max. 250 m for 76800 baud
  • max. 200 m for 115200 baud

Fig. 6 shows the terminal assignment for RS422 communication.
  


Fig. 6

The following lengths are possible for the ET 200S 1SI module as communication module when using the cable type LIYCY 3 x 2& x 0.14:

  • max. 1200 m for 19200 baud
  • max 500 m for 38400 baud
  • max. 250 m for 76800 baud

CM 1241
Fig. 7 shows the terminal assignment for RS485 communication.

You can connect the CM 1241 via a 9-pin PROFIBUS connector and a PROFIBUS bus cable from Siemens.

For this Siemens provides an RS485 bus connector that you can use to connect multiple devices to an RS485 network. This connector has a switch to selectively terminate the network with a terminating resistor. Further information about this is available in section 13.2 of the S7-1200 manual at the link given below.

Note the following features for connectors of your own design:
 

Fig. 7

 
CB 1241
Fig. 8 shows the terminal assignment for RS485 communication.

You can connect the CB 1241 via a PROFIBUS connector and a PROFIBUS bus cable from Siemens.

The CB 1241 provides internal resistors for the network termination, but does not have its own 9-pin female Sub-D connector.

To terminate the connection you connect TRA with TA and TRB with TB to include the internal resistors in the circuit.
 

Fig. 8

   
Further Information
Detailed information about module communication via the RS485 and RS422 interfaces is available in the following manuals.
Security information
In order to protect technical infrastructures, systems, machines and networks against cyber threats, it is necessary to implement – and continuously maintain – a holistic, state-of-the-art IT security concept. Siemens’ products and solutions constitute one element of such a concept. For more information about cyber security, please visit
https://www.siemens.com/cybersecurity#Ouraspiration.