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

116 Chapter5
Using Subsystem Break
Subsystem Break Intrinsics
After XCONTRAP executes, the procedure checks to make sure it
completed successfully. Again, the procedure uses the Pascal/iX
ccode
function to check for errors. If XCONTRAP did not complete
successfully, the user is informed of the failure, and the procedure ends.
If the call to XCONTRAP is successful, the procedure calls
FCONTROL, using a controlcode value of 17. This call actually
enables subsystem break processing and makes it possible for the
application to respond if
[CTRL]Y is entered. Again, the procedure
checks for errors following the call and will inform the user should the
attempt to enable subsystem break fail.
Subsystem break can also be disabled at any time, by calling
FCONTROL again, using 16 as the controlcode value.
Figure 5-2 Procedure to Enable Subsystem Break