Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site pucc-i Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!ihnp4!inuxc!pur-ee!CS-Mordred!Pucc-H:Pucc-I:ad0 From: ad0@pucc-i (Andy Thomas) Newsgroups: net.micro.pc Subject: Re: Homemade AT Serial Port/RS232 Cable - (nf) Message-ID: <816@pucc-i> Date: Mon, 14-Jan-85 16:21:58 EST Article-I.D.: pucc-i.816 Posted: Mon Jan 14 16:21:58 1985 Date-Received: Tue, 15-Jan-85 02:34:06 EST References: <5100034@uiucdcsb.UUCP> Organization: Purdue University Computing Center Lines: 72 Here are the pin assignments of the 9 pin D connector on the IBM PC/AT serial port. Pin Description Signal Source --- ----------- ------------- 1 Carrier Detect modem 2 Receive Data modem 3 Transmit Data PC/AT 4 Data Terminal Re PC/AT 5 Signal Ground 6 Data Set Ready modem 7 Request to Send PC/AT 8 Clear to Send modem 9 Ring In modem Here are the RS-232 Signal Conventions Pin Description Signal Source --- ----------- ------------- 2 Trensmitted Data Terminal 3 Received Data Modem 4 Request to Send Terminal 5 Clear to Send Modem 6 Data Set Ready Modem 8 Carrier Detect Modem 20 Data Terminal Ready Terminal 22 Ring Indicator Modem 7 Signal Ground If you want to use the control signals, you could try the following cable: DB-9 Pin Description DB-25 Pin -------- ----------- --------- 1 Carrier Detect 8 2 Tramsmit Data 3 3 Received Data 2 4 Data Terminal Rdy 20 5 Ground 7 6 Data Set Ready 6 7 Request to Send 4 8 Clear to Send 5 9 Ring Indicator 22 To use a cable with no control signals (known as a null modem cable) try the following: DB-9 Pin Description DB-25 Pin -------- ----------- --------- 2 Tramsmit Data 3 3 Received Data 2 5 Ground 7 DB-9 : Wire pins 7&8 together Wire pins 1,6,&4 together DB-25 : Wire pins 6,8,&20 together Wire pins 4&5 together I have not tried these cables yet, but am sure they will work. Andrew Thomas {dacvax|harpo|ihnp4|inuxc|seismo|ucbvax}|pur-ee|pucc-i:ad0 ( *Not responsible for any damages. Void where prohibited. Penalty required for early withdrawl..............)