Topic List

Click a topic to learn more.


Term of the Moment

Bitcoin confirmation


Look Up Another Term


Redirected from: EIA-232

Definition: RS-232


(Recommended Standard-232) A TIA/EIA standard for serial transmission. Although employed for numerous other purposes, the RS-232 serial port was widely used on earlier personal computers prior to USB (see serial port). The RS-232 cable limitation of 50 feet can be extended to several hundred feet with high-quality cable.

Although RS-232 defines the signals for 25 lines, many applications use less than a dozen, which is why both DB-25 and DB-9 connectors are used. RS-232 transmits positive voltage for a 0 and a negative voltage for a 1. In 1984, RS-232 was officially renamed TIA/EIA-232-E. See RS-232/485.

          Pin Settings for Plug
       (Reverse order for socket.)
  ______________________________________
  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

           _________________
             1  2  3  4  5
               6  7  8  9


 25 pin                        9 pin

  1 - PG   Protective ground
  2 - TD   Transmitted data     3
  3 - RD   Received data        2
  4 - RTS  Request to send      7
  5 - CTS  Clear to send        8
  6 - DSR  Data set ready       6
  7 - SG   Signal ground        5
  8 - CD   Carrier detect       1
  9 - + voltage (testing)
 10 - - voltage (testing)
 11 - 
 12 - SCD  Secondary CD
 13 - SCS  Secondary CTS
 14 - STD  Secondary TD
 15 - TC   Transmit clock
 16 - SRD  Secondary RD
 17 - RC   Receiver clock
 18 - 
 19 - SRS  Secondary RTS            9 pin
 20 - DTR  Data terminal ready      4
 21 - SQD  Signal quality detector
 22 - RI   Ring indicator           9
 23 - DRS  Data rate select
 24 - XTC  External clock
 25 -




A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
misc