Advantech PCM-9570/S 2006957006 5th Edition - Manual (Page 113)

Appendix C Pin Assignments 101
Table C-19: COM2 port for RS-232, RS-422 and RS-485 (CN20)
Pin Signal
RS-232
RS-422 RS-485
11 DCD2 TX- DATA-
13 RxD2 TX+ DATA+
15 TxD2 RX+ NC
17 DTR2 RX- NC
19 GND GND GND
12 DSR2 DSR2 (not used) DSR2 (not used)
14 RTS2 RTS2 (not used) DSR2 (not used)
16 CTS2 CTS2 (not used) DSR2 (not used)
18 RI2 RI2 (not used) DSR2 (not used)