Data Overruns on Modem/Serial Line with VT320?

Data Overruns on Modem/Serial Line with VT320?

Post by Trevor Jenki » Thu, 25 Apr 1996 04:00:00

I have a VT320 connected to my Linux machine running kernel 1.2.8. The
VTs setup has modem lines enabled. The serial port (ttyS3) is driven
by a 16550. I have added the following to /etc/inittab

s3:45:respawn:/sbin/agetty19200 ttyS3

When I login on this port there are signs that occasional data
overruns are occuring, e.g. there are  lost characters, there are
corrupted characters. However, there are no entries in
/var/adm/messages for ttyS3, except root logins---it is a secure tty.
I have noticed this corruption in two scenarios (1) when accessing
files CD-ROM and (2) when using "less". In case (1) it does not matter
whether the files are being accesed from an Xterm session or from the
VT320. In case (2) it only happens if less is accessing the file
directly---if it is in a pipe then there is no corruption or character
loss. (My CD-ROM drive, a Panasonic DR-U124X-4, is connected to a
BusLogic BT-445C SCSI controller.) I have checked that there are no
IRQ conflicts with either the software or hardware (that was the cause
of an earlier problem with the VT320 where it wold take 10 seconds for
any character to be processed).

What can I do to elimiate  the corrupted characters and regain the
lost cahracters? By the way I want the terminal setup with No XOFF---I
like using ^s as my search character in emacs and I do not want random
searches to be initiated when the terminal wants to throttle back on
the I/O.

Regards, Trevor.

Procrastinate Now!


1. overruns on 38400 bps serial line to SG workstation


Hi all,
I've been configuring the /dev/cua0 serial line of my
Compaq laptop to talk to a Silicon Graphics tty port. It
works fine at 9600 bps (!), using cu -l /dev/cua0 -s 9600 on
the Linux side. This is a cheap way to connect and transfer
files to a common workstation. I tried to speedup the link
to 38400 bps, using cu -l /dev/cua0 -s 38400, and modifying
the /etc/inittab accordingly on the SG, and this works fine
too... most of the time! I sometimes get input overruns on
/dev/cua0 while transfering large files (1Mb). No such
problem occurs at 9600 bps.

Did anybody have similar problems and hopefully found a
correct setup (RTS/CTS and such)?

Thanks in advance

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