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Date: Sun 15-Jun-1989 16:28:15 From: Unknown Subject: dumb terminal dumb I'm having some difficulty connecting a dumb terminal to my cube. A perfectly good null-modem cable results in data travelling succesfully from the NeXT to my adm3a, but nothing goes the other way. Has anyone else struggled with this, or is it as easy as it should be, implying that I've got a hardware problem somewhere? >From: johnl@ima.ima.isc.com (John R. Levine)
Date: Sun 16-Jun-1989 01:10:22 From: Unknown Subject: Re: dumb terminal dumb In article <9001@phoenix.Princeton.EDU> andy@phoenix.Princeton.EDU (Andrew M. Milburn) writes: >I'm having some difficulty connecting a dumb terminal to my cube. >A perfectly good null-modem cable results in data travelling succesfully >from the NeXT to my adm3a, but nothing goes the other way. The problem is that the NeXT is RS422 while your terminal is RS232. I had exactly the same problem trying to hook up an IBM PS/2-50 as a terminal. Turns out that the NeXT is using levels of (roughly) +5 and ground, while the terminal wants +5 and -5. Many RS232 receivers are forgiving enough to accept +5/0 but others aren't. Another terminal might work better.
Date: Sun 16-Jun-1989 16:41:05 From: Unknown Subject: Re: dumb terminal dumb In article <4076@ima.ima.isc.com> johnl@ima.UUCP (John R. Levine) writes: >In article <9001@phoenix.Princeton.EDU> andy@phoenix.Princeton.EDU (Andrew M. Milburn) writes: >>I'm having some difficulty connecting a dumb terminal to my cube. >>A perfectly good null-modem cable results in data travelling succesfully >>from the NeXT to my adm3a, but nothing goes the other way. > >The problem is that the NeXT is RS422 while your terminal is RS232. I had >exactly the same problem trying to hook up an IBM PS/2-50 as a terminal. >Turns out that the NeXT is using levels of (roughly) +5 and ground, while the >terminal wants +5 and -5. Many RS232 receivers are forgiving enough to >accept +5/0 but others aren't. Another terminal might work better. I once solved this problem for (don't laugh) a Commodore 64. I might be able to dig up my notes if someone is interested, but the general idea is to hook up one or two MC1488/MC1489 line driver/receiver chips (I forget which is which right now) and a +12/-12V supply (or two 9V bateries). A simple terminal interface can be done with two chips, a modem interface probably requires at least one more. See the Motorola Data sheets on these chips. It costed me all of three bucks and two hours work on the C-64. #include <std.disclaimer> Mike Macgirvin mike@relgyro.stanford.edu (36.64.0.50) >From: bruceh@zygot.UUCP (Bruce Henderson)
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