Department of Computer Scien

ce and Information Engineering

National Cheng Kung University

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BASICS OF SERIAL COMMUNICA-TIONRS232 Standards(cont’)

RS232 Connector DB-9

Ring indicator (RI)

9

Clear to send (-CTS)

8

Request to send (-RTS)

7

Data set ready (-DSR)

6

Signal ground (GND)

5

Data terminal ready (DTR)

4

Transmitted data (TxD)

3

Received data (RxD)

2

Data carrier detect (-DCD)

1

Description

Pin

RS232 DB-9 Pins

‰Since not all pins are used in PC cables, IBM introduced the DB-9 version of the serial I/O standard