Asynchronous Serial Communications Programmer's Reference Manual (32022-90052)

Chapter 8 175
Intrinsics Reference
FCONTROL(16, 17)
FCONTROL(16, 17)
Parameters
controlcode 16 — Disables the subsystem break function.
17 — Enables the subsystem break function.
param 16-bit unsigned integer by reference
(required)
This parameter has no meaning for these controlcode
values. Enter a dummy value of 0 to satisfy the internal
requirements of the intrinsic.
Notes A call to FCONTROL with a controlcode value of 16
or 17 determines whether or not a terminal will react to
a subsystem break request. (The default subsystem
break character is
[CTRL]Y.) Use 16 to disable
subsystem break, 17 to enable subsystem break.
Subsystem break is initially disabled on all devices; it
must be specifically enabled before it can be used. It is
available only for devices running sessions, and has no
effect on programmatically controlled devices.
Subsystem break is reset to the disabled state at
FCLOSE.
If enabled, subsystem break allows the terminal user to
stop a program local or subsystem local command. It is
invoked in standard editing mode by the
end-of-medium (EM) character, produced on HP
terminals by typing
[CTRL]Y.
Even when subsystem break is enabled for a terminal
connected via PAD, subsystem break must be followed
by a
[Return] to signal the PAD that data is ready to be
forwarded.
You can also use FDEVICECONTROL to alter the
subsystem break character in either standard or
transparent mode. See the discussion of the
FDEVICECONTROL intrinsic later in this chapter for
the proper parameter settings to use for this purpose.
In transparent editing mode, you are allowed to define
a different character to be used to invoke subsystem
break by specifying the new character as part of param
in a call to FCONTROL(41).