RS232 (Serial/COM Line) Pin Assignments

 

Male 25-pin connector with "sex organs" pointing at the viewer:

Remember - Mirror Image if you're looking at a female connector. (9-pin information below) 
        ---------------------------------------------------------
         \  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   /
           ---------------------------------------------------
PINDIRREQNAMEMEANING
1-mGNDChassis Ground
2OYTDTransmit Data
3IYRDRecieve Data
4OmRTSRequest To Send
5ImCTSClear To Send
6ImDSRData Set Ready
7-YSGSignal Ground
8ImDCDData Carrier Detect
9----
10----
11--STFSelect Transmit Frequency
12I--Secondary Data Carrier Detect
13I--Secondary Clear To Send
14O--Secondary Transmit Data
15I-DCETransmission Signal Element Timing
16I--Secondary Receive Data
17I--Receiver Signal Element Timing
18----
19O--Secondary Request To Send
20OmDTRData Terminal Ready
21I-SQSignal Quality Detector
22I-RIRing Indicator
23--DTEData Signal Rate Selector
24O--Transmit Signal Element Timing
25--BYTest Indicator

KEY
DIRIInput to computer from peripheral
OOutput produced by computer
REQYConnection always required
mConnection only required by a modem
-Connection not required



 

Male 9-pin connector with "sex organs" pointing at the viewer:

Remember - Mirror Image if you're looking at a female connector. (25-pin information above) 
        -------------------------
         \  1   2   3   4   5  / 
          \   6   7   8   9   /
           -------------------
PINDIRREQNAMEMEANING
1ImDCDData Carrier Detect
2IYRDRecieve Data
3OYTDTransmit Data
4OmDTRData Terminal Ready
5-YSGSignal Ground
6ImDSRData Set Ready
7OmRTSRequest To Send
8ImCTSClear To Send
9I-RIRing Indicator

KEY
DIRIInput to computer from peripheral
OOutput produced by computer
REQYConnection always required
mConnection only required by a modem
-Connection not required