Specifications

Processor Description (V40)
Check Index
The purpose of the check index instruction is to test the index of an
array against an upper and lower limit. The CHKIND [BOUND]
instruction generates a check index interrupt if the index value is less
than the lower limit or greater than the upper limit. The vector for the
check index instruction is fixed at 5 and is not maskable.
Variable Vector
Instruction
Interrupts can be generated using a variable vector interrupt
instruction with the format BRK [INT] xx, where xx is the vector
number. Accessing subroutines in this manner means only the
subroutine vector is fixed. The location and length of the subroutine
can vary without affecting the main program. These interrupts cannot
be masked.
Emulation
Mode
Two interrupt instructions deal with 8080 emulation mode. The
BRKEM instruction is used to transfer V40 operating modes from
native to emulation for execution of 8080 based programs. The
CALLN instruction is used in emulation mode to call an 8088
procedure. Both instructions have the format and operation of the
variable vector instruction. The following pages discuss 8080
emulation in detail.
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