MPE/iX Intrinsics Reference Manual (32650-90875)

130 Chapter5
Command Definitions (FCONTROL - FLOCK)
FCONTROL
allow system break processing to occur. For example, disable system break
when using block mode. This prevents data loss or corruption that could
occur if
BREAK is pressed during a block mode read.
Reset after FCLOSE.If
BREAK is pressed while system break is disabled, no
action is taken by any level of software. System break has no effect on a
device with no active session.
15/U16 Enable system break function:
Item has no meaning; enter a value of 0 to satisfy internal requirements.
System break is enabled by default for any terminal on which a session is
active. If a user presses
BREAK or the CAUSEBREAK intrinsic is called, the
system attempts to interrupt the processing and place the terminal at the
command interpreter level. Many system commands and program
commands (that invoke subsystems or run user programs) are breakable.
When the system break is enabled and received, EOR, read timer,
terminal mode, and echo values are saved by the DTS software. This
allows restoration when normal processing is resumed. If a system break
is entered during processing of a character mode read or write, data is lost.
Any read that is interrupted by a break is reissued by the system after a
RESUME command is entered.
Some application programs change the settings of terminals and/or the
characteristics of their device files. In these cases, it may be undesirable to
allow system break processing to occur. For example, disable system break
when using block mode. This prevents data loss or corruption that could
occur if
BREAK is pressed during a block mode read.
Reset after FCLOSE. (Default) If
BREAK is pressed while system break is
disabled, no action is taken by any level of software. System break has no
effect on a device with no active session.
16/U16 Disable subsystem break function:
Item has no meaning; enter a value of 0 to satisfy internal requirements.
Subsystem break is initially disabled on all devices; it must be 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 disabled at FCLOSE.
When enabled, the user can stop a program-local or subsystem-local
command. It is invoked by the subsystem break character. (The default
subsystem break character is
CTRLY.)
When enabled for a terminal connected through PAD, the subsystem break
must be followed by
RETURN to signal the PAD that data is ready.
Before enabling the subsystem break, call the XCONTRAP intrinsic to arm
the subsystem break trap procedure. When a subsystem break is entered,
the subsystem break trap is disarmed. The RESETCONTROL intrinsic must
be called to allow another subsystem break to occur.