* IM 2: Vector provided by I register and external data
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| IFF1 || 1-bit || Main Instruction Fetch Flip-Flop || Set when interrupts are enabled, cleared on disable
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| IFF2 || 1-bit || Store the state of IFF1 buffer during Non-Maskable Interrupts (NMI) || Allows interrupts When an NMI occurs, the processor clears IFF1 to be enabled disable interrupts temporarily.IFF2 stores the previous state of IFF1 so that after the instruction following EINMI is handled, IFF1 can be restored to its original state.
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| WZ || 16-bit || Internal temporary register pair. Also known as MEMPTR || Used for memory and address calculations