ESCAPE_WAIT Device Parameter
If your terminal:
- Suffers from output corruptions when using an Attached Printer
and/or Multiple Sessions, or
- Displays data to the wrong device (eg. data for the Attached Printer
appears on the terminal),
then modifying the escape_wait parameter may solve your problem.
Many terminals and printers use multi-character escape sequences to
control the cursor position and enhancement of data (eg. bold, inverse).
When both a Terminal and its Attached Printer are operating simultaneously,
the board software transparently inserts escape sequences to direct
output to the appropriate device.
Often an escape sequence will only be partially output when it is time
to switch output to the other device. When this happens, most terminals
get confused, the desired switch is not performed and the corruption
described results.
To solve this problem, a timer (set to the value of the ESCAPE_WAIT
period) is started whenever a port sends an escape character.
Switching to the alternate device will be inhibited until the ESCAPE_WAIT
period has elapsed. The timer is re-started if another escape
character is sent within the ESCAPE_WAIT period.
The default value of the ESCAPE_WAIT period for all devices is 80 clock
ticks (ie. 80/100ths of a second).
To modify the Escape_Wait parameter:
Step 1.
Highlight Select on the Main Menu and press <Enter>, highlight
the panel containing the relevant port and press <Enter>.
Step 2.
Highlight Select on the Configuration Menu and then the port supporting
the Device and press <Enter>.
Step 3.
Highlight Options on the Port Configuration Menu and press <Enter>.
Step 4.
Highlight the Device option and the Device Type in the Device Table
and press <Enter>.
Step 5.
Change the ESCAPE_WAIT parameter and press <Enter> to execute.
Device Flow Control
Characters
This section is relevant only if your system uses software flow control
characters other than ^S and ^Q.
If a device is receiving characters faster than it can process them,
the device will request the port to stop sending characters. When
it is ready to receive again, it will request the character flow be
re-started. The board software uses two characters, Vstop
(usually ^S) to pause the flow, and Vstart (usually ^Q) to re-start
the flow.
To modify Vstop and Vstart:
Step 1.
Highlight Select on the Main Menu and press <Enter>, highlight
the panel containing the relevant port and press <Enter>.
Step 2.
Highlight Select on the Configuration Menu and press <Enter>,
and then highlight the port supporting the Device and press <Enter>.
Step 3.
Highlight Options on the Port Configuration Menu, press <Enter>.
Step 4.
Highlight the Device option and the Device Type in the Device Table
and press <Enter>.
Change the Vstart and Vstop values and press <Enter> to execute.
RS-485 Support
RS-485 is an upgraded version of RS-422-A. It uses the same signal
levels but extends the number of peripherals to which a computer can
interface. Additionally, RS-485 allows for bi-directional multi-point
party line communication and can effectively be used for 'mini-LAN'
applications eg. between point of sale terminals and a central computer.
When using RS-485 party line communications, enabling and disabling
of the transmitter is achieved by toggling the DTR signal. The following
command configures the driver to perform DTR toggling automatically
on a particular port:
/usr/lib/easyio/bin/bccstty
-d <device> dtrfollow
where <device> refers to the port device name eg. /dev/tty1a00.
This command should be added to a startup script so that it is executed
after easyadm has configured the devices. The ATA startup script is
located in a file called S30easy. For most operating systems, this script
is located in the /etc/rc2.d directory. The script that contains the
bccstty command could be called S31easy
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