Specifications

Processor Description (V40)
CPU restores the PSW [FL], PS [CS], and PSP [IP]. The single-step
interrupt is not masked by the IE [IF] bit in the PSW [FL].
Non-Maskable
The V40 has a non-maskable interrupt input called NMI. NMI is
rising edge triggered but must remain active for two CPU clocks to
guarantee recognition. This interrupt is not maskable and the vector is
fixed at 2.
Fixed Vector
Instruction
The fixed vector instruction (BRK3 [INT3]) is a special form of the
more general variable vector instruction. The difference is that the
fixed vector is a single byte while the variable vector requires 2 bytes.
The primary use of this instruction is for breakpoint execution during
program development. Because it is a single byte, the instruction can
be mapped over the smallest possible instruction. This interrupt is not
maskable and has a fixed vector of 3.
Overflow
The overflow interrupt is generated if the V [OF] flag is set to a
logical 1 and the BRKV [INTO] instruction is executed. This
interrupt is useful for trapping overflow errors for mathematical
operations. The overflow interrupt is not maskable and the vector is
fixed at 4.
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