MPE/iX Intrinsics Reference Manual (32650-90905)

Chapter 5 131
Command Definitions (FCONTROL - FLOCK)
FCONTROL
Subsystem break processing is summarized as follows:
1. A user-written procedure must be provided defining how the subsystem
break trap handler will react upon receipt of a subsystem break. The
user program must contain:
• The user written procedure.
• A call to XCONTRAP, specifying the external label of the procedure;
this arms the subsystem break trap.
• A call to FCONTROL
Itemnum =17, enabling the subsystem break
function.
• A call to RESETCONTROL when the program is ready to receive
another subsystem break.
2. A new subsystem break character can be defined through FCONTROL
Itemnum =41 if the terminal is placed in transparent mode or through
FDEVICECONTROL, which allows a subsystem break character to be
defined without placing the device in the transparent mode.
3. At any time, FCONTROL can be called to disable the subsystem break.
Reset in break mode; reset after FCLOSE. (Default)
17/U16 Enable 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.
Subsystem break processing is summarized as follows:
1. A user-written procedure must be provided defining how the subsystem
break trap handler will react upon receipt of a subsystem break. The
user program must contain:
• The user written procedure.
• A call to XCONTRAP, specifying the external label of the procedure;
this arms the subsystem break trap.
• A call to FCONTROL
itemnum =17, enabling the subsystem break