Aaeon PCM-4894 User Manual page 22

The mainboard offers four serial ports: three RS-232 and one RS-
232/422/485. These ports allow you to connect them to serial
devices (mouse, printers, etc.).
COM1
COM2
COM3
COM4 31
16 PCM-4894 User Manual
PIN SIGNAL
1 DCDA
3 RXDA
5 TXDA
7 DTRA
9 GND
11 DCDB
(422TXD-/485DATA-)
13 RXDB
(422TXD+/485DATA+)
15 TXDB
(422RXD+)
17 DTRB
(422RXD-)
19 GND
21 DCDC
23 RXDC
25 TXDC
27 DTRC
29 GND
DCDD
33 RXDD
35 TXDD
37 DTRD
39 GND
PIN SIGNAL
2 DSRA
4 RTSA
6 CTSA
8 RIA
10 N.C.
12 DSRB
14 RTSB
16 CTSB
18 RIB
20 N.C.
22 DSRC
24 RTSC
26 CTSC
28 RIC/+5V/+12V
30 N.C.
32 RSRD
34 RTSD
36 CTSD
38 RID/+5V/+12V
40 N.C.