RS232 (V.24) Technical Reference
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RS232 has been around for a long time. It works by setting the signals to either a mark (> 9V, typically 12V) and space (< -9V, typically -12V). As you can imagine this 24V swing is pretty noisy and can cause a lot of cross talk at higher speeds. That is why it typically does not go much faster than 128Kbps.
This has been modernized into the 9 pin com port on the PC and sometimes used on a RJ11 (phone jack).
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DB-25
Pin# |
DB-9
Pin# |
RJ-45
Pin# |
Common
Name |
EIA
Name |
CCITT
Circuit# |
DTE-DCE
Direction |
Signal Description |
| 1 |
|
|
FG |
AA |
101 |
|
Frame Ground |
| 2 |
3 |
6 |
TD |
BA |
103 |
 |
Transmitted Data, TxD |
| 3 |
2 |
5 |
RD |
BB |
104 |
 |
Received Data, RxD |
| 4 |
7 |
8 |
RTS |
CA |
105 |
|
Request To Send |
| 5 |
8 |
7 |
CTS |
CB |
106 |
|
Clear To Send |
| 6 |
6 |
1 |
DSR |
CC |
107 |
|
Data Set Ready |
| 7 |
5 |
4 |
SG |
AB |
102 |
|
Signal Ground, GND |
| 8 |
1 |
2 |
DCD |
CF |
109 |
|
Data Carrier Detect |
| 9 |
|
|
|
|
|
|
+P |
| 10 |
|
|
|
|
|
|
-P |
| 11 |
|
|
|
|
|
|
Unassigned |
| 12 |
|
|
SDCD |
SCF |
122 |
|
Secondary Data Carrier Detect |
| 13 |
|
|
SCTS |
SCB |
121 |
|
Secondary Clear To Send |
| 14 |
|
|
STD |
SBA |
118 |
|
Secondary Transmitted Data |
| 15 |
|
|
TC |
DB |
114 |
|
Transmission Signal Element Timing |
| 16 |
|
|
SRD |
SBB |
119 |
|
Secondary Received Data |
| 17 |
|
|
RC |
DD |
115 |
|
Receiver Signal Element Timing |
| 18 |
|
|
|
|
|
|
unassigned |
| 19 |
|
|
SRTS |
SCA |
120 |
|
Secondary Request To Send |
| 20 |
4 |
3 |
DTR |
CD |
108.2 |
|
Data Terminal Ready |
| 21 |
|
|
SQ |
CG |
110 |
|
Signal Quality Detector |
| 22 |
9 |
|
RI |
CE |
125 |
|
Ring Indicator |
| 23 |
|
|
|
CH/CI |
111/112 |
|
Data Signal Rate Selector |
| 24 |
|
|
|
DA |
113 |
|
Transmitter Signal Element Timing |
| 25 |
|
|
|
|
|
|
Unassigned |
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| UnBalanced RS232 (V.24)
The typical unbalanced driver is the standard RS232 1488 IC, however this requires + and - 12 Volts. Many of the new interfaces are using the V.24 / RS232 driver chips with the charge pump built in, so they only need +5V to operate. These come in many configuration some include both drivers and recievers. Two parts that come to mind is the DS14C232 from TI or Max 232.
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| UnBalanced RS232 (V.24) Receiver
The typical IC used for the reciever is the 1489, it only requires 5 volts to operate, but most new designs are using the charge pump IC which have both the receivers and drivers in the same chip.
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RS232 Breakout, Testing and Conversion
ADVICE manufactures unique products for adapting RS232/V.24 to other standard interfaces:
The UMATS and Exchanger allow conversion between many types of interface: RS232 to V.35, RS449 or
RS530.
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Legal Disclaimer
Advanced IC Engineering (ADVICE) makes no warranties with respect to this documentation and disclaims any implied warranties of merchantability and fitness for a particular purpose. ADVICE assumes no responsibility for any errors that may appear on this site. The information contained on this site is subject to change without notice and does not represent a commitment on the part of ADVICE.
If you have comments or questions about the information presented, please contact us.
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