{| class="wikitable" style="white-space: nowrap;"
|-
! Mode !! Cycles !! M-Cycle Sequence (Acknowledge) !! Vector Source / Action Effect !! Description
|-
| Non-Maskable Interrupt || 11 (5, 3, 3) || M1, Int(1), MW (Push PCH), MW (Push PCL) || iff2 := iff1, iff1 := 0, sp -= 2, (sp) := pc, pc := 0066h || Highest priority interrupt. Cannot be disabled by `DI`. Fixed vector address. Saves previous IFF1 state.