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From: veit@borneo.gmd.de (Holger Veit)
Subject: Re: Regarding Cables on com [NetBSD-0.9]
Message-ID: <1993Sep26.170855.27095@gmd.de>
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References: <283pb6$ier@sylvester.cc.utexas.edu>
Date: Sun, 26 Sep 1993 17:08:55 GMT
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>Okay, I've had problems with both my com ports and lpt ports, first under
>386BSD-0.1 + pk0.2.3, and now NetBSD-0.9.
>Until now, I keep getting the "are you sure all the lines run thru?" response.
>Yes. But not sure exactly whether they run to the right places or not.
>Here is the results of the continuity test, please, someone with experience
>and/or a reference manual handy, tell me if these are correct.
>"Com" port cable,
>9-pin Female D-shell to 25-pin Male D-shell
>Counted from top right Counted from top left
>1 8 (DCD)
>2 3 (RXD)
>3 2 (TXD)
>4 20 (DTR)
>5 7 (SGD)
>6 6 (DSR)
>7 4 (RTS)
>8 5 (CTS)
>9 22 (RNG)
This is a correct 9-to-25 cable (at least from the numbering, look at
the connectors itself; they should have numbers printed on the soldering
side) to connect the computer to a standard modem, which is exactly what
you tried (from reading further, with slip). I cannot check my
own cable now, because I am connected by modem just now, but I have
a copy of the IBM tech ref manual for the serial/parallel adapter here,
which describes exactly your cabling.
Fortunately you didn't want to have a "correct Null-Modem cable"
which is one of the most controversal items in the interfacing world.
>Symptoms: Under both NetBSD-0.9 and all pk levels of 386BSD-0.1,
>if data was sent "out" through FTP, (e.g. "put" when invoked locally,
>"get" when FTP invoked from foreign machine) then RD and SD lights
>blink like crazy, SD almost constant, RD only occasionally.
With e.g. a zmodem transfer to a remote system, this is normal
behavior for a modem connection.
>Three seconds later, CTS goes out. RD and SD lights continue to blink
CTS-off signals to the computer that the input buffer of the modem is
almost full, and the computer should not send further data. It goes up
again when the modem can accept data again. It seems the serial driver
ignores this signal. Since I have seen RTS/CTS flow control working on
my system with TE/2 or Telix (and 386bsd-pk0.2.4, com driver), it might
be bad hardware or - which is possible as well - a wrong or missing
jumper. My 4-serial line board has many, of course undocumented, jumpers,
labeled DSR/DTR/CTS/RTS/DCD which seem to open the corresponding
line from the RS232 driver to the connector. This should make sense for
connecting a terminal TXD/RXD/GROUND only, but can cause certainly
interesting effects with a modem.
>like crazy. Six seconds later, CD EC and OH go out. Slip attempts
This may be an overrun effect on the modem.
>to reopen the line (I can see SD/RD blink a few times) but then the machine
>crashes HARD.
This is certainly not normal. But the message from VM system I sometimes
get with slip ("VM object something ... not clean", 386bsd & FreeBSD,
I've seen this reported with emacs some time ago) isn't kosher as well.
>[RS]D=receive,send data CTS=clear to send CD=carrier detect EC=error correct
>OH=off hook
>
>lpt problem detailed in next article.
>--
>Protect our endangered bandwidth - reply by email. NO BIG SIGS!
>VaX#n8 vax@ccwf.cc.utexas.edu - Don't blame me if the finger daemon is down
--
Dr. Holger Veit | INTERNET: Holger.Veit@gmd.de
| | / GMD-SET German National Research | Phone: (+49) 2241 14 2448
|__| / Center for Computer Science | Fax: (+49) 2241 14 2342
| | / P.O. Box 13 16 | Had a nightmare yesterday:
| |/ Schloss Birlinghoven | My system started up with
53731 St. Augustin, Germany | ... Booting vmunix.el ...