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Stefan ArentzandClaude Opus 4.8
3e7474ac9f
The first phase of the AppleMouse II card (plans/20260721-01): the reusable IRQ machinery the mouse (and later Mockingboard) needs. Dormant in production — no device asserts the line yet — so no existing test moves. CPU (ewm-core): - Split BRK from a hardware IRQ, which shared one BRK-shaped code path. A real `cpu.irq()` now pushes the *exact* resume PC with B **clear** and vectors $FFFE; `nmi()` matches via $FFFA. BRK keeps its own path (`brk_interrupt`): PC+1 with B **set**. A shared `enter_interrupt` helper carries the three. Dormann (which exercises BRK) is byte-identical. - Tests: a hardware IRQ pushes the exact PC / B=0 / masks I / RTI resumes; BRK pushes PC+1 / B=1 — the two stay distinct. Machine (ewm/two.rs): - `Two` caches the maskable IRQ line as one bool; `service_irq()` polls it between `cpu.step()`s in both burst loops (SDL `run`, headless `serve`). Level-sensitive and gated by I: high + I==0 takes the IRQ (which sets I, so the handler runs to RTI); SEI holds it pending until CLI; a low line is never taken. Just a `bool && I` check per step — the line is refreshed on state change, never scanned per instruction (the hazard the plan flags). - Test: the line is level-sensitive and I-gated. `set_irq_line` is a test-only hook until Phase M4 wires the mouse device's asserted state. Kickoff decisions recorded in the plan (owner directed one PR per phase; relative/captured coords; firmware-default clamp; Two-local IRQ line; scripted M4 gate). Gates: cargo fmt / clippy -D warnings / cargo test (370 pass, incl. Dormann, two_timing, and the golden-BMP screenshots — the burst-loop change is inert). Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>