# rtl/intc

Interrupt controller scaffolding. Matches `docs/contracts/intc.md`.

## Current contents

- `intc_stub.sv` — generic PS2-style INTC register shell.
  Register-visible INTC_STAT / INTC_MASK (offsets parameterized) plus a
  16-source injection port `irq_src[15:0]`. The aggregate output
  `cpu_irq` is polarity-neutral: the same module is instantiated both
  as the EE INTC and as the IOP INTC (with appropriate offsets and a
  different set of wired sources in each case).

## Register semantics

- `INTC_STAT` (offset is a parameter; default 0x00): W1C on writes;
  sticky until cleared. `irq_src` sets bits on each cycle they're
  observed; same-cycle inject-over-W1C collisions keep the pending bit
  — interrupts are never silently swallowed.
- `INTC_MASK` (offset is a parameter; default 0x10): plain write-to-set.
  Real PS2 uses XOR/toggle semantics on mask writes; stub uses plain
  write for simplicity. Escalate if a BIOS trace demands it.

## Instantiation conventions

- **EE INTC**: default offsets (STAT=0x00, MASK=0x10). Instantiated
  stand-alone in most benches; the EE memory map does not route INTC
  addresses yet (deferred).
- **IOP INTC**: parameterized to STAT=0x70, MASK=0x74 to match real
  PS2 IOP INTC placement. Reached through `iop_memory_map_stub` at
  physical address 0x1F80_1070+ (region id = 5).

## Wired sources (current)

- EE INTC bit 0 = EE DMAC completion (`dmac_reg_stub.irq_completion_o`).
- IOP INTC bit 0 = IOP DMAC ch9 completion
  (`iop_dmac_reg_stub.irq_completion_o`).

Both are one-cycle pulses driven from the respective DMAC's `S_DONE`
state. The INTC latches them into its own pending bit; software (the
TB, for now) reads STAT through the architectural register port and
acks with a W1C write.

## Scope boundary

Module is side-neutral by design. Source-routing from other real
subsystems (timers, GIF/GS, IPU, SPU2, bridge `last_seen_o`) is the
next natural expansion. Re-arm / re-assertion ordering is already
proven in the integration benches.