The 8051 Microcontroller and Embedded

Department of Computer Scien

ce and Information Engineering

National Cheng Kung University

HANEL

BASICS OF SERIAL COMMUNICA-TIONRS232 Standards(cont’)

RS232 DB-25 Pins

Transmit signal element timing

24

Secondary data carrier detect

12

Data signal rate select

23

Unassigned

11

Ring indicator (RI)

22

Reserved for data testing

9/10

Unassigned

25

Secondary clear to send

13

Signal quality detector

21

Data carrier detect (-DCD)

8

Data terminal ready (-DTR)

20

Signal ground (GND)

7

Secondary receive data

19

Data set ready (-DSR)

6

Unassigned

18

Clear to send (-CTS)

5

Receive signal element timing

17

Request to send (-RTS)

4

Secondary receive data

16

Received data (RxD)

3

Transmitted signal element timing

15

Transmitted data (TxD)

2

Secondary transmitted data

14

Protective ground

1

Description

Pin

Description

Pin

RS232 Connector DB-25