RS232 interface

Last Updated : Aug 19, 2025 |
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The following image and table show the connectors of the RS232 cable interface and their functions:
A diagram showing RS232 cable connectors
Number
Function
1.
Data Terminal Ready (DTR), the device is ready to communicate.
2.
Data Set Ready (DSR), the device is ready to communicate.
3.
Transmit Data (TxD), transmits bytes out of the device.
4.
Ground (GND), ground connection.
5.
Receive Data (RxD), receives bytes into the device.
6.
Ground (GND), ground connection.
7.
IR OUT
8.
No Connection (NC)
The following table shows the correspondence between RS232 and DB-9 connectors:
RS232
DB-9
1. DTR
6. DSR
2. DSR
4. DTR
3. TXD
2. RXD
4. GND
5. GND
5. RXD
3. TXD
6. GND
1. CD
7. IR OUT
7. RTS
8. NC
8. CTS
—
9. RI
The following table shows the correspondence between RS232 and a mini-DIN connector:
RS232
Mini-DIN
1. DTR
2. DSR
2. DSR
1. DTR
3. TXD
5. RXD
4. GND
4. GND
5. RXD
3. TXD
6. GND
6. GND
7. IR OUT
7. NC
8. NC
8. NC