RS232 DB9 Connector

DB-9M
Function
Abbreviation
Pin #1
Data Carrier Detect
CD
Pin #2
Receive Data
RD or RX or RXD
Pin #3
Transmitted Data
TD or TX or TXD
Pin #4
Data Terminal Ready
DTR
Pin #5
Signal Ground
GND
Pin #6
Data Set Ready
DSR
Pin #7
Request To Send
RTS
Pin #8
Clear To Send
CTS
Pin #9
Ring Indicator
RI

RS232 DB9 Male

 

RS232 DB25 Connector

RS-232 Serial PC Port Connector DB-25
DB-25M Function Abbreviation
Pin #1 Chassis/Frame Ground GND
Pin #2 Transmitted Data TD
Pin #3 Receive Data RD
Pin #4 Request To Send RTS
Pin #5 Clear To Send CTS
Pin #6 Data Set Ready DSR
Pin #7 Signal Ground GND
Pin #8 Data Carrier Detect DCD or CD
Pin #9 Transmit + (Current Loop) TD+
Pin #11 Transmit - (Current Loop) TD-
Pin #18 Receive + (Current Loop) RD+
Pin #20 Data Terminal Ready DTR
Pin #22 Ring Indicator RI
Pin #25 Receive - (Current Loop) RD-

RD232 DB25 Male

RS530 DB25

1 Shield(A)
2 Transmitted Data(A)
3 Received Data (A)
4 Request to Send (A)
5 Clear to Send (A)
6 DCE Ready (A)
7 Signal Ground
8 Received line Signal Detector (A)
9 Receiver Signal Element Timing - DCE (B)
10 Received line Signal Detector (B)
11 Transmitter Signal Element Timing DTE (B)
12 Transmitter Signal Element Timing DCE (B)
13 Cear to Send (B)
14 Transmitted Dota (B)
15 Transmitted Signal Element DCE (A)
16 Received Data (B)
17 Receiver Signal Element Timing DLE (A)
18 Local Loopback
19 Request to Send
20 DTE Ready (A)
21 Remote loopback
22 DCE Ready (B)
23 DTE Ready (B)
24 Tronsmitter Signal Element Timing DTE (A)
25 Test Mode

RS-530 supersedes RS-449 and complements RS-232. Based on a 25 pin connection, it works in conjunction with either electrical interface RS-422 (balanced electrical circuits) or RS-423 (unbalanced electrical circuits). RS-530 defines the mechanical/electrical interfaces between DTEs and DCEs that transmit serial binary data, whether synchronous or asynchronous. RS-530 provides a means for taking advantage of higher data rates with the same mechanical connector used for RS-232. However, RS-530 and RS-232 are not compatible! RS-530 accommodates data transmission rates from 20 Kbps to 2 Mbps; maximum distance depends on which electrical interface is used. RS-530 is compatible with these standards: ITU V.10, V.11, X26; MIL-188/114; RS-449.

 

Connecting DB25 to DB9 serial connectors, and suggestion for MOD-TAP serial connectors (e.g. to use RJ45 connectors )

DB25  DB9
  8    1   CD -----  (this is an input)
  3    2   RXD    |
  2    3   TXD    |
 20    4   DTR-----  (this is an output)
  7    5   SGND   |
  6    6   DSR-----  (this is an input)
  4    7   RTS
  5    8   CTS
 22    9   RI
For IBM terminals, you need to connect pins 1+4+6 together and connect pins 7+8 together

Other common pinout for commercially sold DB25 to DB9 cables: 1-4 & 5, 2-2, 3-3, 4-6, 5-7, 6-20, 7 & 8-8, 9-22

A suggestion for MOD-TAP serial connectors; using RJ45 connectors with WearComp to save space

This proposed standard originates from the VT320 terminals described below:

Wiring to connect a VT320 to a DB9 male connector for use on waverider, etc. VT320 cable (looking at connector with wire facing away): 

|6 2 5 5 3 4|
|           |
|  _________|
|__|
Wiring to connect a VT320 to a DB25 male connector for use on modem, etc. VT320 cable (looking at connector with wire facing away): 
|6 3 7 7 2 20|
|            |
|  _________ |
|__|
The above connection strategy is also useful for MOD-TAP connectors, so that you can use a reversed-sense crimp-on phone wire as a null modem.

MOD-TAP connectors save space, e.g. all you need is RJ45 connectors on the WearComp instead of the much larger DB9 serial connectors. That means you can typically fit four serial ports into a small space, less space than even the two regular DB9 serial connectors.

Also, a 4 conductor phone wire will give you basic connectivity (Tx,Rx,SGND) while a 6 conductor phone wire will give full capability (DTR and DSR)