RS232 422 485.doc

1、 DB-25 pin assignments Pin Name Signal Pin Name Signal - 1 FG Frame ground 14 STD Secondary TD 2 TD Transmitted data 15 TC Transmit clock 3 RD Received data 16 SRD Secondary RD 4 RTS Request to send 17 RC Receive clock 5 CTS Clear to send 18 - Unassigned 6 DSR Data set ready 19 SRTS Secondary RTS Da

2、ta 7 SG Signal ground 20 DTR terminal ready 8 DCD Data carrier 21 SQ Signal quality signal detector 9 - Positive 22 RI Ring voltage indicator 10 - Negative 23 DRS Data rate voltage selector Clock 11 - Unassigned 24 SCTE transmit external 12 SDCD Secondary 25 BUSY Busy DCD 13 SCTS Secondary CTS DB-9

3、pin assignments DB-9 Corresponding Pin DB-25 Pin Signal Function - 2 2 TD Transmitted data 3 3 RD Received data 8 4 RTS Request to send 7 5 CTS Clear to send 6 6 DSR Data set ready 5 7 SG Signal ground 4 8 DCD Data carrier detect 1 20 DTR Data terminal readyNormal DTE-DCEThise wirings can be used wi

4、th normal Data Terminal Equipment (DTE) to Data Communications Equipment (DCE) connections. The wiring are standard way to do asyncronous DTE to DCE connection and they support hardware handshaking. Good wires for PC to modem connections. 9 pin to 25 pin wiring can also be used for making 9 pin to 2

5、5 pin connector adapters. DTE (25 pin) DCE (25 pin) TD 2 - 2 RD 3 4 CTS 5 6 DCD 8 - 8 DTR 20 - 20 SG 7 - 7 RI 22 2 RD 2 4 CTS 8 6 DCD 1 - 8 DTR 4 - 20 SG 5 - 7 RI 9 2 RD 3 - 3 RTS 4 -, ,- 4 CTS 5 5 DSR 6 6 DCD 8 8 DTR 20 - - 20 SG 7 - 7 DTE (9 pin) DCE (25 pin) TD 3 - 2 RD 2 - 3 RTS 7 -, ,- 4 CTS 8

6、5 DSR 6 6 DCD 1 8 DTR 4 - - 20 SG 5 - 7Null modem cableThis cable can be used when you must connect two DTE equipments like computers to each other directly without using any data communication quipment in between computers. This wiring supports hardware handshaking. DTE (25 pin) DTE (25 pin) TD 2 -

7、 /- 2 RD 3 3 RTS 4 - /- 4 CTS 5 5 DSR 6 6 DCD 8 8 DTR 20 -/ - 20 SG 7 - 7 DTE (25 pin) DTE (9 pin) TD 2 - /- 3 RD 3 2 RTS 4 - /- 7 CTS 5 8 DSR 6 6 DCD 8 1 DTR 20 -/ - 4 SG 7 - 5 DTE (9 pin) DTE (9 pin) RD 2 - /- 2 TD 3 3 RTS 7 - /- 7 CTS 8 8 DSR 6 6 DCD 1 1 DTR 4 -/ - 4 SG 5 - 5Two-wire DTE-DTE conn

8、ectionThis cable can be used when you must connect two DTE equipments like computers to each other directly without using any data communication quipment between computers. This wiring needs only two signal wires and ground between computers but does not support hardware handshaking. DTE (25 pin) DT

9、E (25 pin) TD 2 - /- 2 RD 3 3 RTS 4 -, ,- 4 CTS 5 5 DSR 6 6 DCD 8 8 DTR 20 - - 20 SG 7 - 7 DTE (25 pin) DTE (9 pin) TD 2 - /- 3 RD 3 2 RTS 4 -, ,- 7 CTS 5 8 DSR 6 6 DCD 8 1 DTR 20 - - 4 SG 7 - 5 DTE (9 pin) DTE (9 pin) TD 3 - /- 3 RD 2 2 RTS 7 -, ,- 7 CTS 8 8 DSR 6 6 DCD 1 1 DTR 4 - - 4 SG 5 - 5PC t

10、o printer cableThis is a wiring for cable for connecting printer to computer. Both printer and computer are DTE quipment and printer uses DTR busy signalling. This is good cable for PC to printer connection when printer uses DTR bysy or XON/XOFF signalling. Computer Printer DTE (25 pin) DTE (25 pin)

11、 TD 2 - 3 RD RD 3 - 2 TD CTS 5 -+- 20 DTR DSR 6 - DCD 8 3 RD RD 2 - 2 TD CTS 8 -+- 20 DTR DSR 6 - DCD 1 -, DTR 4 - SG 5 - 7 SGLoopback testerThis is a simple and useful tool for testing RS-232 ports in DTE equipment are working working or not. This plug is connected so that every sent character is echoed back. DTE (25 pin) TD 2 -, RD