Siemens S7-1200 System Manual page 974

Technical specifications
A.14 Communication interfaces
Table A- 247 Power supply
Technical data
Power loss (dissipation)
Current consumption (SM Bus), max.
Current consumption (24 VDC) max.
CB 1241 RS485 (6ES7 241-1CH30-1XB0)
①
Connect "TA" and TB" as shown to terminate the network. (Terminate only the end devices on the RS485 network.)
②
Use shielded twisted pair cable and connect the cable shield to ground.
You terminate only the two ends of the RS485 network. The devices in between the two end
devices are not terminated or biased. See the S7-1200 System Manual section on "Biasing
and terminating an RS485 network connector"
Table A- 248 Connector pin locations for CB 1241 RS485 (6ES7 241-1CH30-1XB0)
Pin
1
2
3
4
5
6
7
8
974
9-Pin connector
RS485 / Logic GND
RS485 / Not Used
RS485 / TxD+
RS485 / RTS
RS485 / Logic GND
RS485 / 5 V Power
RS485 / Not used
RS485 / TxD-
CB 1241 RS485
1.5 W
50 mA
80 mA
X20
--
--
3 - T/RB
1 - RTS
--
--
--
4 - T/RA
S7-1200 Programmable controller
System Manual, 03/2014, A5E02486680-AG