Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!usc!ucsd!ucbvax!hplabs!hpfcso!hpfcdc!perry
From: perry@hpfcdc.HP.COM (Perry Scott)
Newsgroups: comp.sys.hp
Subject: Re: Beware of serial port programs run by users
Message-ID: <5570380@hpfcdc.HP.COM>
Date: 10 Feb 90 00:23:11 GMT
References: <235@cmic.UUCP>
Organization: HP Ft. Collins, Co.
Lines: 29

Rob explains the externals pretty well.  I've worked with the MUX
firmware, so I can guess what really happens to your MUX.


from /usr/include/sys/termio.h:

#  define       CSTOP   023     /* cntl s */
#  define _CBAUD        0000037
#  define B2400         0000014         /* 2400 baud */
#  define B38400        0000022         /* 38400 baud */

> RAU_Line_Settings.c_cflag = B2400 | CSTOP | CREAD | CS8 | PARENB | PARODD

This sends (023|014 = 037), which is still a baud rate, and gives it to
the MUX.  The MUX firmware uses this as an index into a table of values
which it uses to poke its SIO.  Apparently, the SIO gets poked with
something that is not-your-usual-baudrate, depending on the whim of the
Zilog link editor.

The problem is exacerbated by an old firmware bug that uses only one
configuration byte instead of four.  This causes all the ports to be set
to the never-never-land baud rate, in addition to the victim's.  I'll
bet the EPROM on the MUX says 98642-90001.  If so, there is a (free?)
upgrade to the latest revision.

So, I have to agree with the Response Center that you are using an
"unsupported" baud rate. :-)  Nasty typo you have there.

Perry Scott