julia@mcglin.wpg.com (Julia Crawley) (01/16/91)
In the next few weeks, my organization will be getting a Basic 4 GPX 6270 (i.e., a Sequent). Our vendor is telling us that proper cabling of our in-house terminals will require four pairs? Is this true? Or, will three wires for 2,3,&7 be sufficient? -- Julia Crawley -- (504) 586-1200 julia@mcglin.wpg.com uunet!wpg!mcglin!julia
lwj@cs.kun.nl (Luc Rooijakkers) (01/16/91)
In <14@mcglin.wpg.com> julia@mcglin.wpg.com (Julia Crawley) writes: >In the next few weeks, my organization will be getting a Basic 4 >GPX 6270 (i.e., a Sequent). Our vendor is telling us that proper >cabling of our in-house terminals will require four pairs? Is this >true? Or, will three wires for 2,3,&7 be sufficient? It probably depends on your version of Dynix. When I recently installed a Sequent Symmetry with Dynix 3.0, we indeed needed four wires, since I could not find any way to turn of the carrier detect. If you get Sequent's System V port (Dynix/pts I believe), you might be able to turn it off. Of course, you can also fake it in the connector by connecting the DTR output to the DCD input. By the way, you may actually *want* four wires. It has the very attractive feature of automatically logging you out if you turn off your terminal, which is good for your security. Besides, it usually saves processes. Hope this helps -- Luc Rooijakkers Internet: lwj@cs.kun.nl Faculty of Mathematics and Computer Science UUCP: uunet!cs.kun.nl!lwj University of Nijmegen, the Netherlands tel. +3180652271
scottie@sequent.UUCP (Scott Thurston) (01/17/91)
In article <14@mcglin.wpg.com> julia@mcglin.wpg.com (Julia Crawley) writes:
%In the next few weeks, my organization will be getting a Basic 4
%GPX 6270 (i.e., a Sequent). Our vendor is telling us that proper
%cabling of our in-house terminals will require four pairs? Is this
%true? Or, will three wires for 2,3,&7 be sufficient?
%
%--
%Julia Crawley -- (504) 586-1200
%julia@mcglin.wpg.com
%uunet!wpg!mcglin!julia
You will need a signal driving DCD (pin 8) on the Sequent side of the
connection. If DCD is not high when an open is attempted on the port, the
open will not complete. Commonly, DTR (pin 20) on the terminal is used to
drive DCD on the Sequent. Then, when the terminal is shut off, DCD is
dropped and the port is closed and a HANGUP sent to processes associated
with the port.
-- Scott Thurston UUCP: ...!uunet!sequent!scottie
Technical Support Engineer Internet: scottie@sequent.com
Sequent Computer Systems, Inc (503) 578-3878
15450 SW Koll Parkway
Beaverton, OR 97006daveman@laxsqnt.UUCP (David Mansfield) (01/17/91)
wqb@ufycorp.Unify.Com (Bill Bonney) writes: >In article <14@mcglin.wpg.com> julia@mcglin.wpg.com (Julia Crawley) writes: >>In the next few weeks, my organization will be getting a Basic 4 >>GPX 6270 (i.e., a Sequent). Our vendor is telling us that proper >>cabling of our in-house terminals will require four pairs? Is this >>true? Or, will three wires for 2,3,&7 be sufficient? >> >>-- >>Julia Crawley -- (504) 586-1200 >>julia@mcglin.wpg.com >>uunet!wpg!mcglin!julia >We have a Sequent and are using 3 pair now (I think we use 2, 3, 5, 7, 8 & >20). We are working with a cabling vendor to reduce to 2 pair (2, 3 and >we're working on which other 2 are necessary). We think there will be some >printers we have (we have some old stuff still running) that will still >require 3 pair, but have never needed 4 pair. DCE needs 2, 3, 7, and 8. DTE needs to run 2, 3, 7, and 20: DCE DTE 2 =====> 3 3 =====> 2 7 =====> 7 8 =====> 20 The Sequent ports use pin 8 (DCD) to determine if a device is attached to the port or not. Since most devices hold pin 20 (DTR) high when turned on, you need to map 20 back into 8. Where this falls short is for devices (as Bill mentions, some printers) using hardware handshaking: Dropping DTR cause the port to become "hung up" and the associated process hangs up. There are some other options for how the port and cable can be configured using "ttyconfig" (I'm not sure the MBF machine has this or not). ==== Dave Mansfield ..!sequent!daveman daveman@sequent Sequent Computer Systems, Inc.
csg@pyramid.pyramid.com (Carl S. Gutekunst) (01/18/91)
As you probably already guessed, the number of wires on a tty connection is a religious issue, with some technical considerations. To make the usual ASCII terminal work at all, you need at least 2, 3, and 7. On most UNIX boxes, you also need to drive the incoming carrier detect signal. Most vendors, including Sequent, wire their serial ports as a DTE, so this means pin 8. While you can fake this out at the Sequent end, you don't want to; the DCE sensing not only ensures that turned off terminals will be logged out, it also keeps the computer from echoing garbage to itself on the line. A few terminals, many modems, and virtually all printers implement some kind of hardware flow control, although its virtually always optional. You'll need more wires for those. For intelligent modems you have to figure at least 4 pairs (8 wires). Sequent's Systech terminal mixes don't handle hardware flow control very well, though, so this is not much of an issue in the short term; but plan for down the road. Actually, for modems I would generally advise to stick within RS-232 specs: no more than 50', unless you are using a special low-capacitance cable, in which case you can go to 200' or so. I would *not* recommend connecting pin 1; it creates funny ground problems if you aren't absolutely sure of what you are doing. If using shielded wire, then connect the shield to the connector shell, not to pin 1. (If you aren't using metal-shell connectors, then their's no point in using shielded cable.) <csg>