kevin@msa3b.UUCP (Kevin P. Kleinfelter) (01/18/91)
Recently I posted about a serial port problem. The gist of the problem
was that serial ports were going dead, requiring a reboot to activate them.
In the course of diagnosing the problem, we discovered that "pdisable -a"
did NOT drop DTR to the modems... SOMETIMES. We did not have HUPCL
in LOGMODES for the port, but we did have it for RUNMODES. If someone
had not logged-in on a port, pdisabling the port did not drop DTR.
In other words, if HUPCL is not set (i.e. "stty -hupcl"), then
pdisableing a port does not drop DTR. I assert that this is a bug.
True or false?
GLOSSARY
YAASPP - Yet Another AIX Serial Port Problem
DTR - Data Terminal Ready (If you don't know it, I can't explain it.)
--
Kevin Kleinfelter @ Dun and Bradstreet Software, Inc (404) 239-2347
{emory,gatech}!nanovx!msa3b!kevin
Look closely at the return address. It is nanovx and NOT nanovAx.robin@batcomp.austin.ibm.com (Robin D. Wilson) (01/24/91)
In article <1498@msa3b.UUCP> kevin@msa3b.UUCP (Kevin P. Kleinfelter) writes: >Recently I posted about a serial port problem. The gist of the problem >was that serial ports were going dead, requiring a reboot to activate them. > >In the course of diagnosing the problem, we discovered that "pdisable -a" >did NOT drop DTR to the modems... SOMETIMES. We did not have HUPCL >in LOGMODES for the port, but we did have it for RUNMODES. If someone >had not logged-in on a port, pdisabling the port did not drop DTR. > >In other words, if HUPCL is not set (i.e. "stty -hupcl"), then >pdisableing a port does not drop DTR. I assert that this is a bug. >True or false? Basically, when you set "-hupcl" on a tty, you are telling it, "No matter what else I say, don't drop DTR. (ie. don't hang up and close this port.)" So no, this is not a bug. The way around this problem is to add HUPCL to the "STTY attributes at LOGIN" in SMIT. (BTW, this will become the default at some point in the future.) DTR == Data Terminal Ready, which is a voltage on PIN 20 of the standard RS-232C DB25 connector. When this signal is present, it indicates that the *DTE device is ready to communicate. Normally, this means that the device is plugged in and turned on. When signal is dropped, the *DCE device will assume that DTE device has ended the communication (ie. it was turned off, the wire was cut, it stopped listening to the port.) *DTE == Data Terminal Equipment (ie. Terminals, Computers emulating a terminal, etc.) *DCE == Data Communication Equipment (ie. modems.) -- +-----------------------------------------------------------------------------+ |The views expressed herein, are the sole responsibility of the typist at hand| +-----------------------------------------------------------------------------+ |UUCP: robin%aixserv@uunet.uu.net | |USNail: 701 Canyon Bend Dr. | | Pflugerville, TX 78660 | | Home: (512)251-6889 Work: (512)823-3015 | +-----------------------------------------------------------------------------+