RJ11-RS232

      RJ11-RJ45

      RJ45-RS232

      USB-RS232










rs232 cable
rs232 cable

RS232


For a serial line information arrive at regular intervals (synchronous) or at random intervals (asynchronous).

Between a transmitter (DTE) and a receiver (DCE) wiring is right. RS232 cables can be connected in series.
In configurations where 2 DTE are directly connected, a cable of cross linking or \Null-Modem\ should be used.
This cable has female connectors at each end.








25-pin Null-Modem RS232 connection diagram :







1 MASS 1
2 DATA SHOW 3 CROSS
3 RECEPTION DATA 2 CROSS
4 REQUEST TRANSMISSION 5 CROSS
5 READY FOR TRANSMISSION 4 CROSS
6 DATA 20 CROSS
7 0 ELECTRIC VOLT 7 .
8 DETECTION SIGNAL ONLINE 8 CROSS
9 (+) VOLTAGE 9
10 (-) VOLTAGE 10
11
12 2 ° - SIGNAL DETECTION 12
13 2 ° - READY FOR TRANSMISSION 13 CROSS
14 2 ° - DATA TRANSMISSION 14 CROSS
15 DCE - SIGNAL CLOCK FOR TRANSMISSION 17 CROSS
16 2 ° - DATA RECEPTION 16 CROSS
17 SIGNAL CLOCK FOR RECEPTION 24 CROSS
18 DTE - ASK THE LOCAL DCE LOOPBACK
19 2 ° - TRANSMISSION 19 CROSS
20 DATA SENT 6 CROSS
21 SIGNAL TRANSMISSION QUALITY 21
22 RING INDICATOR 22
23 SIGNAL SPEED SELECTION 23
24 DCE - SIGNAL CLOCK FOR TRANSMISSION 24 CROSS




Connector rs232 25 pins
Connector rs232 25 pins

RS232 UART


To establish communication by an RS232 cable, it is necessary to define the protocol used, in particular the tau of transmission and coding.
In practice UART is the most used.
UART RS232 includes 9 records of 8-bit sorted into three categories :

• Control records : IER, LCR, MCR, DL (16-bit : + DLL DLM).
• Records of States : LSR, MSR and IIR.
• Data : RBR and THR.











rs232 9 pins connector
rs232 9 pins connector

Conversion : DB25 - DB9


The original pinout RS232 was developed for 25-pin (sub-d). Today 9 pins RS232 connectors are commonly used.
In mixed applications, a 9-to-25 converter can be used.







DB9 DB25 FUNCTION
1 8 DETECTED DATA CARRIER
2 3 RECEIVE DATA
3 2 DATA TRANSMISSION
4 20 READY DATA TERMINAL
5 7 SIGNAL MASS
6 6 READY DATA
7 4 REQUEST TO SEND
8 5 CLEAR TO SEND