Configuring Systems for Terminals, Printers, and Other Serial Devices (32022-90051)

Chapter 9 193
Describing Asynchronous Devices
How to Control Terminals
Up to 16 AEOR’s are available but only through the use of
FDEVICECONTROL 192, 66.
System Console Attention Character
When [CTRL]-A is entered on the system console, it signals a [CTRL]-A
console command. The computer sends the system console a carriage
return and line feed along with an equals sign prompt (=), signaling
that it is ready for the command.
[CTRL]-A commands are allowed only
on the system console. For more information on the system console and
its special commands, refer to MPE/iX Managing Peripherals.
NOTE [CTRL]-A is not accepted as a special character from a terminal that is
connected to a DTC.
System Break
Using default operating conditions, the ASC software responds to a
system break signal from the terminal and alerts the computer. The
system break function interrupts the execution of programs,
subsystems, and most MPE/iX commands. Once the program or
subsystem is interrupted, it can be aborted by entering the ABORT
command or the program or subsystem can be restarted by entering the
RESUME command.
To transmit a system break signal, press
[Break]. System break can be
disabled programmatically. Refer to the MPE/iX Intrinsics Reference
Manual for more information on system break.
Some application programs, such as block mode programs, change the
settings of terminals and the characteristics of their device files. These
programs should return the devices to normal operating mode before
they complete.
If a program does not disable break (through the FCONTROL or
FDEVICECONTROL intrinsic), the user can still use
[Break]. If [Break] is
pressed, the program might not be able to recover but the MPE/iX
operating system will by assuming that the terminal is in normal
operating mode.
A VPLUS block mode application can be reset by pressing
[CTRL],
[Shift], and [Reset] simultaneously. Other block mode applications are
harder to reset. Sometimes, it is necessary to turn the terminal off and
on. Other times, the port must be reset. Refer to Troubleshooting
Terminal, Printer, and Serial Device Connections for information on
resetting ports if host-based management is being used. Refer to Using
OpenView DTC Manager for more information on resetting ports if
PC-based management is being used.