Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!bionet!apple!oliveb!amiga!cbmvax!valentin From: valentin@cbmvax.commodore.com (Valentin Pepelea) Newsgroups: comp.sys.amiga.tech Subject: Re: RS232: Connect null modem cable between Amiga 500 and TI99/4A Message-ID: <9237@cbmvax.commodore.com> Date: 8 Jan 90 00:46:40 GMT References: <9001061902.AA03244@ucbvax.Berkeley.EDU> Reply-To: valentin@cbmvax.commodore.com (Valentin Pepelea) Organization: Commodore, West Chester, PA Lines: 61 In article <9001061902.AA03244@ucbvax.Berkeley.EDU> 11TSTARK@GALLUA.BITNET (Timothy Stark) writes: > > I want transfer my files between my Amiga 500 and TI-99/4A computers. > > > Amiga 500 Connector TI-99/4A RS232 Connector > > 1 GND Ground 1 GND Ground > 2 TXD Transmit Data 2 RD Receive Data > 3 RXD Receive Data 3 TX Transmit Data > 4 RTS Request to send 5 CTS Clear to send > 5 CTS Clear to send 6 DSR Data Set Ready > 6 DSR Data Set Ready 7 GND Ground > 7 GND Ground 8 DCD Detect Carrier > 8 DCD Carrier Detect 20 DTR Data Terminal Ready > 9 +12 12 volts > 10 -12 12 volts > 11 AUDO Audio output > 18 AUDI Audio input > 20 DTR Data Terminal Ready > 22 RI Ring Indicator > >My TI-RS232 Manual says that DTR is require for operation why that it >refuse to work!! > >I will consider to connect null modem cable with 4 wires: RXD, TXD, DSR, >and DTR. Perhaps It will work well. Null-modem cables are made like this: Amiga Amiga 1 --------- 1 Shield GND 2 ---\ /--- 2 Transmit Data (TXD) X 3 ---/ \--- 3 Receive Data (RXD) 7 --------- 7 Signal GND Only pins 2,3 & 7 are necessary to operate successfully. Some equipment like Ganhalf's GLMs allow you to use only 2 & 3. Connect pins 1 to the shield of the cable only if excessive noise is picked up. So we see that what one computer transmits through the TXD pins gets received by the RXD pin of the other computer. Your TI computer has already switched these two signals on its port, therefore the null-modem cable will not work here. A straight 25 cable will not work either, because signals 6 and 20 also have to be switched when used. Just don't connect them if you want no hassles. But if you insist connect them like pins 2 & 3: 6 ---\ /--- 6 Data Terminal Ready (DTR) X 20 ---/ \--- 20 Data Sender Ready (DSR) Valentin -- The Goddess of democracy? "The tyrants Name: Valentin Pepelea may distroy a statue, but they cannot Phone: (215) 431-9327 kill a god." UseNet: cbmvax!valentin@uunet.uu.net - Ancient Chinese Proverb Claimer: I not Commodore spokesman be