emux_stty(1) General Commands Manual emux_stty(1)
NAME
- set the options for a port on the HP PCI/EISA Mux.
SYNOPSIS
options]
DESCRIPTION
The command options are used to turn on and off a number of special flags used for controlling driver I/O processing on a PCI/EISA Multi-
plexer (Mux) port. These commands are enhancements to the standard commands, and will affect the operation of the port.
Several options address problems encountered with software flow control when trying to run at high speeds. This type of problem typically
occurs when the application fails to properly initialize the tty port using software flow control. At low speeds (i.e., 9600 baud or less)
the problems are not evident because flow control is not typically invoked by the terminal. The HP PCI/EISA Mux card has the ability to
output sustained high-speed data without degradation. This will sometimes break programs that may operate properly at low speeds or with
lower performance multiplexer cards.
Many of the output modes are implemented in the PCI/EISA Mux hardware. This allows greater throughput with less CPU processing overhead
than other serial I/O devices. There are some features which are still handled by the line discipline and the use of these features
results in traditional CPU overheads and throughput.
If is not enabled then maximum output performance will be achieved. Even if is enabled, the following settings are handled in the hardware
and maximum output performance will still be maintained.
The use of other settings will result in additional software overhead on output characters.
Use of "raw" mode on input will also maximize throughput and reduce CPU processing overheads. However, even in raw mode some and settings
require line discipline intervention. Applications that want maximum throughput and/or minimal CPU overhead should avoid the following
settings:
The line discipline also supports the "block mode" feature. When a device is in "block mode", software overhead is introduced to handle
the device protocol and the benefits of the PCI/EISA Mux hardware are also mitigated.
By default, the PCI/EISA mux driver automatically bypasses the line discipline whenever possible to maximize performance. However, the
user can disable this automatic bypass of the line discipline using the and options described later. This may be needed for applications
that rely on certain behaviors of the line discipline.
The special options permit programs with this problem to be run at high speeds without requiring the application to be modified. The use of
these features is transparent to the user.
The commands are usually enabled at the terminal using the format:
emux_stty [+(-) option]
or, they may be entered from the console, and redirected to the port in which they are to take effect. For example,
emux_stty [+(-) option] < /dev/tty2a1
See below for the new naming conventions used for HP PCI/EISA Mux ports.
DISPLAY OPTIONS
To see the complete list of available options and syntax for the command, enter without options. The commands are:
Report the current settings of the emux_stty options.
Display the HP PCI/EISA Mux hardware configuration, including
the logical card number, ID, slot, and type of the cards that are installed and configured.
Use emux_stty dtr 1 to force the DTR control signal high, regardless of the application. (dtr 0 causes a return to the default DTR behav-
ior).
Ignore (do not ignore) the
option, which permits any character to act as an XON character for resuming output.
A number of applications enable the feature in the standard profile. This destroys the integrity of software flow
control because any user type ahead is erroneously interpreted as an XON after the terminal sends an XOFF. The
command is provided to correct the most common application-related problems experienced when running terminals at
high speed.
NOTE: is transparent to users. It should always be set for terminal speeds above 9600bps when hardware flow con-
trol is not used.
Ignore (do not ignore) the
option, which is used by some applications to disable XON/XOFF software flow control. Setting this option forces
the driver to apply XON/XOFF flow control to the port, regardless of whether or not the application has set
Enter (exit) physical loopback mode. This is a good test for the
wiring and hardware because characters typed at the terminal are echoed back to the terminal. If no characters
show up back at the terminal, this may indicate a wiring problem. Do not enter the command directly from a termi-
nal. When the terminal is placed in the loopback mode, you are not able to enter any more commands! Powering the
terminal off and on does not help.
Always redirect the command from the console to the port in question, e.g., entering
Lock (unlock) a port's parameters (speed, character size, etc.),
so that subsequent commands to the port are ignored (can be executed).
Bypass (do not bypass) standard line discipline processing,
on either input ( or output ( respectively.
These options are provided to support applications which rely on special code embedded in the line discipline, and
may have trouble running with the line discipline being bypassed.
Force a printer port to stay open even if the application attempts to close it. (-lp returns the port to normal operation). This is useful
because the spooler does not always reset the parameters correctly when the port is closed at the end of a print
job. After this command is entered any attempts to close the port will be ignored.
Display the current status of the RS-232 modem control
signals (RTS, CTS, DSR, DCD, DTR, and RI) for a port.
Resume output on flow controlled ports. If a port is
flow controlled (i.e., it receives an XOFF), the process is put to sleep until an XON is received to unblock the
process and permits it to be killed.
This option can only be executed by a user with root capability, since it accesses a privileged file.
To restart port /dev/tty2a1, enter the command
NOTE: The device file name must contain only the instance number, port module and port number when used with the
option.
Display the hardware status registers of a port.
This option can only be executed by a user with root capability, since it accesses a privileged file.
To display the hardware status registers for port /dev/tty2a1, enter the command
NOTE: The device file name must contain only the instance number, port module and port number.
Forces a port to honor and pass (not pass) XON/XOFF software flow
control, until the port is closed, or the option is disabled. This is useful for applications that need to see
XON/XOFF characters.
NAMING CONVENTION
HP PCI/EISA Mux ports use the following syntax for naming device files:
where categoties are:
tty = direct connect
ttyd = modem dial-in
cul = modem dial-out
cua = modem dial-out with automatic caller;
refers to a device instance number;
refers to a port module whose legal range is 'a' to 'h';
and
refers to a port number whose legal range is 1 to 16.
SEE ALSO
emux_diag(1M), stty(1), termio(7), modem(7).
emux_stty(1)
