TOPS-10 Monitor Calls Manual Volume 2 AA-K039D ... - Trailing-Edge

APRENB [CALLI 16]
NOTES
o If your trap-servicing routine
instruction
JRSTF @.JBTPC
contains
the
the processor bits are cleared and the stat~ of
the CPU is restored; control resumes where the
interrupt occurred.
o
The APRENB monitor call clears the trap after an
occurrence of any selected condition; therefore
your program must call APRENB after each trap
occurs.
o To enable repeated trap interceptions, your
program should set AP.REN (bit 18) when executing
the APRENB call; however, clock interrupts must be
reenabled after each trap occurs.
o
If your
overflow
but the
fatal errors.
program does not enable for traps,
conditions and clock ticks are ignored,
other conditions listed above produce
EXAMPLE
OVERFL:
CONTIN:
MOVE I
MOVEM
MOVE I
APRENB
JRST
OUTSTR
JRSTF
TI,OVERFL ;Get address of overflow handler
TI, .JBAPR ;Put into .JBAPR
TI,AP.AOV ;Arithmetic overflow flag
TI, ;To .JBAPR on arith ovflw
CONTIN iOn to something else
[ASCIZ /ARITHMETIC OVERFLOW ERROR/]
@.JBTPC ;Resume execution
;Something else
This code sequence sets up an overflow. message for the first
arithmetic overflow; note that this example will not handle more than
one arithmetic overflow.
COMMON PROGRAMMING ERRORS
o
o
Not reenabling the interrupt after each trap has occurred.
Failing to set up .JBAPR prior to the APRENB call.
RELATED CALLS
o
o
PISYS.
UTRP.
22-6