串口RS232引腳定義

1 邏輯電平

EIA-RS-232C 對(duì)電器特性、邏輯電平和各種信號(hào)線功能都作了規(guī)定。

在TxD和RxD上：

邏輯1(MARK)=-3V～-15V

邏輯0(SPACE)=+3～+15V

在RTS、CTS、DSR、DTR和DCD等控制線上：

信號(hào)有效（接通，ON狀態(tài)，正電壓）＝+3V～+15V

信號(hào)無(wú)效（斷開(kāi)，OFF狀態(tài)，負(fù)電壓)=-3V～-15V

2. 引腳定義

針腳 定義 符號(hào)

1 載波檢測(cè) DCD?????????? Pin 1 Received Line Signal Detector(Data Carrier Detect)

2 接收數(shù)據(jù) RXD?????????? Pin 2 Received Data

3 發(fā)送數(shù)據(jù) TXD?????????? Pin 3 Transmit Data

4 數(shù)據(jù)終端準(zhǔn)備好 DTR?? Pin 4 Data Terminal Ready

5 信號(hào)地 SG??????????????? Pin 5 Signal Ground

6 數(shù)據(jù)準(zhǔn)備好 DSR??????? Pin 6 Data Set Ready

7 請(qǐng)求發(fā)送 RTS???????????Pin 7 Request To Send

8 清除發(fā)送 CTS?????????? Pin 8 Clear To Send

9 振鈴提示 RI???????????? Pin 9 Ring Indicator

3. 9針和25針串口引腳對(duì)應(yīng)關(guān)系

4? 連線方法

Usually Not.?While the normal PC hardware might well run with just Tx, Rx and Ground connected, most driver software will wait forever for one of the handshaking lines to go to the correct level. Depending on the signal state it might sometimes work, other times it might not. The reliable solution is to loop back the handshake lines if they are not used.

http://airborn.com.au/serial/rs232.html

5? 串口RS232數(shù)據(jù)幀格式

在串口的總線上，高電平是默認(rèn)電平，當(dāng)一幀數(shù)據(jù)開(kāi)始傳輸時(shí)，必須先把總線拉低一位作為起始位