Hello!
My original question was:
> I have a decoder to get news that I save my computer. I am getting an error
> mesage which is:
> acerint: overrun error; status = 63
> ace0: input silo overflow
> I would like to know if I could do something to avoid it.
I forgot to say that I have a Alpha 255 running DU3. Anyway I got an answer from
Dr Tom Blim explaining how flow control works that has been very helpfull.
Thanks.
The answer was:
> That message usually is generated on the newer computer models that use the
> "ace" driver for serial lines. There is a family of serial I/O chips that
> are supported by the driver. The newer chips all support high line speeds
> and have buffering in the chip to attempt to avoid these data overruns.
> There are two kinds of flow control that can be used to help support input
> of serial data. With software flow control (the default), the characters
> XON and XOFF (control-Q and control-S respectively) are sent by the host to
> advise the terminal (your news feed) when to resume (XON) or stop (XOFF) the
> transmission of data.
> There is also hardware flow control, in which a modem control signal (CTS)
> is toggled to indicate whether the host is ready to receive data.
> Software flow control is enabled by default and has been present in UNIX
> since the early days (before there was a Digital UNIX).
> In Digital UNIX V4.0 and later, the use of hardware flow control can be set
> with the "stty" program.
> To set hardware flow control on your COM1 port (ace0), use this command as
> root:
> stty -f /dev/tty00 crtscts
> and used
> stty -a -f /dev/tty00
> to verify that it is set. See the "stty" reference page for details.
> Once you set RTS/CTS hardware flow control on a line, it will remain in
> effect until you disable it, or until the system is restarted. If you start
> your news feed processing from a shell script, put the stty command to set
> hardware flow control in that script.
> For this to work, there has to be full transmission of modem signals from
> your system to the news feed. If this is done with a "null modem" cable,
> the cable has to carry ALL the signals, not just the data, in order for the
> hardware flow control to work, and the news feed hardware has to honor the
> signals (just as it would have to recognize and obey software flow control
> for that to work).
> If you can't get flow control working between the host system and the news
> feed, then you're going to continue to see data overruns.
> Even if flow control is implemented correctly, if the host system does not
> service the serial I/O port in a timely manner when an interrupt occurs (due
> to data arriving), you can still get overruns. In this case, you might need
> to slow the transmit rate.
> Tom
Received on Thu Apr 24 1997 - 09:44:01 NZST