Siemens SIMATIC PC RI25/45 Technical Description page 41

COM1 Port
The port is designed for RS 232. New transfer modes are used, for example,
for converting a parallel port to an SCSI or to an IDE port. Each mode has an
individual pinout.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Pin numbers 9, 10, 18, 19, and 21 are unassigned for the different versions of
the motherboard for the SIMATIC PC RI25/45 and must not be used for any
other purpose.
SIMATIC PC RI25/45, Technical Description
C79000-G7076-C808-01
Pin Description
No.
Shield
Transfer data
(TxD/D1)
Receive data
(RxD/D2)
Request to send
(RTS/S2)
Clear to send
(CTS/M2)
Data set ready
(DSR/M1)
Functional ground
(GND/E2)
Data carrier detect
(DCD/M5)
+TTY Receive data
(RxD)
–TTY Receive data
(RxD)
unassigned
unassigned
unassigned
unassigned
unassigned
unassigned
unassigned
+TTY Transfer data
(TxD)
Current source, isolated
Data terminal ready
(DTR/S1)
–TTY Transfer data
(TxD)
Incoming call
(RI/M3)
unassigned
unassigned
unassigned
Motherboard
Input/Output
Output
Input
Output
Input
Input
Input
Input
Input
Output
Output
Output
Input
2-19