RS-232 and RS-422 Serial Connectors

Table 7-3. DB-9 Pin Assignments

Pin	RS-232 Mode	RS-422 Mode
1	DATA CARRIER DETECT (DCD)	RESERVED
2	RECEIVE DATA (RXD)	RECEIVE DATA (RXD)
3	TRANSMIT DATA (TXD)	TRANSMIT DATA (TXD)
4	DATA TERMINAL READY (DTR)	TRANSMIT DATA+ (TXD+)
5	GROUND	SIGNAL GROUND
6	DATA SET READY (DSR)	RECEIVE DATA+ (RXD+)
7	REQUEST TO SEND (RTS)	OUTPUT HANDSHAKE (HSKo)
8	CLEAR TO SEND (CTS)	INPUT HANDSHAKE (HSKi)
9	NOT CONNECTED	RESERVED

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