Serial Port for PC, XT, PS/2 ============================ (RS232C industry standard) Pin # code description Pin # code description 1 AA ground 13 SCB sec. clear to send 2 BA transmitted data 14 SBA sec. transmitted data 3 BB received data 15 DB transmitted signal 4 CA request to send element timing (DCE) 5 CB clear to send 16 SBB sec. received data 6 CC data set ready 17 DD receiver signal element 7 AB signal ground timing (DCE) 8 CF received line signal 18 - unassigned detector 19 SCA sec. request to send 9 - reserved 20 CD data terminal ready 10 - reserved 21 CG signal quality detector 11 - unassigned 22 CE ring indicator 12 SCF sec. received line 23 CH/CI data signal rate select signal detector 24 DA trans. sig. timing (DTE) 25 - unassigned Serial Port DB9 AT ================== 5 o o o o o 1 6 o o o o 9 Pin Description 1 CD in data carrier detect 2 RD in serial receive data 3 TD out serial transmit data 4 DTR out data terminal ready 5 gnd signal ground 6 DSR in data set ready 7 RTS out request to send 8 CTS in clear to send 9 RI in ring indicator Various Serial Cable Pinouts (like symbols mean connect pins together) ====================================================================== IBM-PC Hayes Modem IBM-AT Hayes Modem DB-25 DB-25 DB-9 DB-25 FGND 1 ------- 1 FGND DCD 1 <------ 8 DCD XMT 2 ------> 2 XMT RCV 2 <------ 3 RCV RCV 3 <------ 3 RCV XMT 3 ------> 2 XMT RTS 4 ------> 4 RTS DTR 4 ------> 20 DTR CTS 5 <------ 5 CTS SGND 5 ------- 7 SGND DSR 6 <------ 6 DSR DSR 6 <------ 6 DSR SGND 7 ------- 4 SGND RTS 7 ------> 4 RTS DCD 8 <------ 8 DCD CTS 8 <------ 5 CTS DTR 20 ------> 20 DTR RNG 9 <------ 22 RNG RNG 22 <------ 22 RNG Null Modem Cable Null Modem Cable IBM PC IBM PC IBM AT IBM AT DB-25 DB-25 DB-9 DB-9 XMT 2------------ 3 RCV RCV 2------------ 3 XMT RCV 3------------ 2 XMT XMT 3------------ 2 RCV RTS 4-# *- 4 RTS RTS 7-# *- 7 RTS CTS 5-# *- 5 CTS CTS 8-# *- 8 CTS DSR 6-+ @- 6 DSR DSR 6-+ @- 6 DSR DCD 8-+ @- 8 DCD DCD 1-+ @- 1 DCD DTR 20-+ @-20 DTR DTR 4-+ @- 4 DTR SGND 7------------ 7 SGND SGND 5------------ 5 SGND Null Modem Cable IBM PC IBM AT DB-25 DB-9 XMT 2------------ 2 RCV RCV 3------------ 3 XMT RTS 4-# *- 7 RTS CTS 5-# *- 8 CTS DSR 6-+ @- 6 DSR DCD 8-+ @- 1 DCD DTR 20-+ @- 4 DTR SGND 7------------ 5 SGND VT 220 Brother M 1509 P-E 6100 Brother M-1509 DB-9 DB-25 DB-25 DB-25 GND 1------- 1 GND GND 1------- 1 GND XMT 2------- 3 RCV XMT 2------- 2 RCV RCV 3------- 2 XMT RCV 3------- 3 XMT DSR 6-------20 DTR RTS 4------- SGND 7------- 7 SGND CTS 5------- DSR 6------- SGND 7------- 7 SGND DCD 8------- DTR 20------- Various serial cable pinouts ============================ NEC NEC IBM-AT 3510/3515 IBM-XT 3510/3515 (DB9) (DB25) (DB25) (DB25) RCV 2------- 2 XMT XMT 2------- 3 RCV XMT 3------- 3 RCV RCV 3------- 2 XMT SGND 5------- 7 SGND CTS 5-------19 2nd RTS CTS 8-------19 2nd RTS SGND 7------- 7 SGND DCD 1 # * 4 RTS DSR 6 # * 4 RTS DTR 4 # * 5 CTS DCD 8 # * 5 CTS DSR 6 # + 6 DSR DTR 20 # + 6 DSR RTS 7 + 8 DCD RTS 7 + 8 DCD RNG 9 +20 DTR RNG 9 +20 DTR IBM-AT NEC 7700 Series (DB9) DCD 1-+-----20 DTR DSR 6-+ RCV 2------- 2 XMT XMT 3------- 3 RCV DTR 4-----+- 6 DSR +- 8 DCD SGND 5------- 7 SGND RTS 7------- 5 CTS CTS 8-------19 2nd RTS IBM-AT HP 7470A IBM-XT HP 7470A (DB9) (DB25) (DB25) (DB25) RCV 2------- 2 XMT GND 1------- 1 GND XMT 3------- 3 RCV XMT 2------- 3 RCV SGND 5------- 7 SGND RCV 3------- 2 XMT DSR 6-+-----20 DTR CTS 5-+-----20 DTR CTS 8-+ DSR 6-+ SGND 7------- 7 SGND IBM-AT HP Laserjet IBM-XT HP Laserjet RCV 2------- 2 XMT GND 1------- 1 GND XMT 3------- 3 RCV XMT 2------- 3 RCV SGND 5------- 7 SGND RCV 3------- 2 XMT DSR 6-+-----20 DTR CTS 5-+-----20 DTR CTS 8-+ DSR 6-+ SGND 7------- 7 SGND IBM-AT Pinout Names IBM-XT Pinout Names 1 DCD Data Carrier Detect 1 FGND Frame Ground 2 RCV Receive Data 2 XMT Transmit Data 3 XMT Transmit Data 3 RCV Receive Data 4 DTR Data Terminal Ready 4 RTS Request to Send 5 SGND Signal Ground 5 CTS Clear to Send 6 DSR Data Set Ready (In) 6 DSR Data Set Ready 7 RTS Request to Send 7 SGND Signal Ground 8 CTS Clear to Send 8 DCD Data Carrier Detect 9 RNG Ring Indicator 20 DTR Data Terminal Ready 22 RNG Ring Indicator Data Terminal to Data Communications ==================================== Data Terminal Data Comm. Data Terminal Data Terminal Equipment <--> Equipment Equipment <--> Equipment Typical Configuration Typical Configuration (DTE) (DTE) (DTE) (DCE) AT XT Printer AT XT Modem 1 FGND--------- 1 FGND 1 FGND----------- FGND 3 2 XMT---------> 3 RCV 3 2 XMT-----------> 2 XMT 2 3 RCV<--------- 2 XMT 2 3 RCV<----------- 3 RCV 7 4 RTS<--------- 5 CTS 7 4 RTS-----------> 4 RTS 8 5 CTS---------> 4 RTS 8 5 CTS<----------- 5 CTS 6 6 DSR<-+-------20 DTR 6 6 DSR<----------- 6 DSR 1 8 DCD<-+ 5 7 SGND----------- 7 SGND +-> 6 DSR 1 8 DCD<----------- 8 DCD 4 20 DTR-------+-> 8 DCD 4 20 DTR----------->20 DTR 5 7 SGND----------7 SGND 9 22 RNG<-----------22 RNG 9 22 RNG 22 RNG Null Modem ========== RS-232C Null Modem RS-232C Straight RS-232C typical Cable Connections through (computer serial printer (computer to computer) to modem) 2 ----------- 3 2 ----------- 2 7 ----------- 7 3 ----------- 2 3 ----------- 3 2 ----------- 3 4 ----------- 5 4 ----------- 4 5 ---| 5 ----------- 4 5 ----------- 5 6 ---|------- 20 6 ----------- 20 6 ----------- 6 8 ---| 7 ----------- 7 7 ----------- 7 1 ----------- 1 20 ---------- 6 20 ---------- 20