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The top left corner is 1, the bottom right corner is 9
9-pin RS232 serial port
(
DB9
)
Pin
Name
Function
1
CD
Carrier detect
2
RXD
Receive data
3
TXD
Send data
4
DTR
Data terminal ready
5
GND
Signal ground
6
DSR
Data ready
7
RTS
Request to send
8
CTS
Clear to send
9
RI
Ring alert
As the RS232 interface has the above electrical characteristics, it can only realize
point-to-point communication.
RS232 communication wiring diagram is shown in the figure below:
2. RS422
The full name of RS422 interface standard is "Electrical Characteristics of
Balanced Voltage Digital Interface Circuit", which defines the characteristics of the