Siemens Simatic M7-400 Reference Manual page 507

13.4.1 Pin Assignments
Socket X1, X2 COMa, COMb
Table 13-8
1 DCD
2 RxD
3 TxD
4 DTR
5 Signal GND
6 DSR
7 RTS
8 CTS
9 RI
Note
Operational ground (signal GND) at the COMa or COMb ports is referenced to
internal ground.
Suitable measures may be required on the process side to avoid ground loops.
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
Socket X1, X2 IF 962-COM (9-Pin Sub D Plug Connector)
Receive signal level
Receive data
Transmitted data
Data terminal ready
Operational ground (GND
Data set ready
Request to send
Clear to send
Ring indicator (incoming call)
Interface Submodules
Input
Input
Output
Output
) –
int
Input
Output
Input
Input
13-11