Path: utzoo!mnetor!uunet!cbmvax!rutgers!ucla-cs!zen!ucbvax!hplabs!hpda!athertn!ericb From: ericb@athertn.Atherton.COM (Eric Black) Newsgroups: comp.sys.amiga Subject: Re: RS232 indignation Message-ID: <156@teak.athertn.Atherton.COM> Date: 7 Jan 88 21:29:29 GMT References: <2292@crash.cts.com> Reply-To: ericb@athertn.UUCP (Eric Black) Organization: Atherton Technology, Sunnyvale, CA Lines: 70 Summary: Make the signals "unisex" as well as the connector In article <2292@crash.cts.com> haitex@pnet01.cts.com (Wade Bickel) writes: >glee@cognos.uucp (Godfrey Lee) writes: >>In article <2188@crash.cts.com> haitex@pnet01.cts.com (Wade Bickel) writes: >>> If the standards people wanted to do things RIGHT, they would >>> have made only one connector type. >>> [UniSex cables!] >> >>That's just wonderful! What type of connector do you suggest the box have, >>male? female? Arrrgh. > > Perhaps a visual example will suffice: > [pictorial of hermaphroditic connectors] Side note: one common example of such connectors: many brake/signal light connectors for trailers have this general form, although in this case it's not so much to allow for "unisex cables" as it is a polarity safeguard (you can only plug it in one way). You may have seen these things. Back to the point of the cable, since the connector is obviously (!) solvable... One of my previous companies (Functional Automation, Inc.) standardized all our RS-232 cables as follows (the "Functional Standard"): 1 - male-to-female cables were straight-through 2 - male-to-male or female-to-female cables crossed signals as necessary to make them "hermaphroditic" [see modem signal disclaimer in (5) below] 3 - short "adapters" were bolted onto equipment, changing connector sex and jumpering RS-232 signals as necessary to make the cable end of the adapter conform to the Functional Standard (including swapping of TD/RD and buggering of DCD/DTR/DSR/RTS/CTS if required) 4 - as a result, IF it could physically be plugged in, the data signals would WORK 5 - the Functional Standard allows for data interchange (TD/RD), handshake (RTS/CTS), and plug-check (DTR/DSR) signals. These families of signals are sufficient for most (?) uses of RS-232 links OTHER THAN connection to modems (which is, of course, the only thing that the RS-232 definition was originally meant to cover). Connections between modems (Data Communications Equipment, or DCE) and computers or terminals (Data Terminal Equipment, or DTE) uses the RS-232 signals as defined in the standard. Connections other than DTE to DCE follow the Functional Standard, with "standardizing adapters" permanently attached to the equipment as required. Our convenient mnemonic was to assign "sex" to the connector pins. Pins 2, 4, and 20 were male, i.e. data/signal comes OUT, and pins 3, 5, and 6 were female, i.e. data/signal goes IN. The adapters made everything work just fine. The adapters only have to be configured ONCE for each particular equipment example, but making them by hand with a soldering iron can be a pain (but there are cheapie import varieties of a poor-man's breakout patch box nowadays which make it very simple). As a result, we never had to scramble for the "right" cable (the one with the wires moved around for the X piece of equipment), and the RS-232 breakout box (those things are worth their weight in gold, and RS-232 data analyzers are worth their weight in platinum, and heavier besides) is needed only once. --------- "Anyone who uses the terms 'RS-232' and 'standard' in the same sentence has never been in the Real World." -- Eric Black "Garbage in, Gospel out" UUCP: {sun!sunncal,hpda}!athertn!ericb Domainist: ericb@Atherton.COM