Struct NullBus 

pub struct NullBus;

A no-op Bus (all reads open, writes dropped) for unit-testing the CPU in isolation.

Trait Implementations

impl Bus for NullBus

fn read24(&mut self, _addr24: u32) -> u8

Read a byte at a 24-bit address (no clock advance — the CPU sequences timing via Bus::advance around this call).

fn write24(&mut self, _addr24: u32, _val: u8)

Write a byte at a 24-bit address (no clock advance — see Bus::read24).

fn access_cycles(&self, _addr24: u32) -> u32

Master clocks this access costs (ares CPU::wait): the region-variable access speed (FastROM vs SlowROM, WRAM, I/O). Defaults to the SlowROM/internal-cycle cost of 6.

fn advance(&mut self, _clocks: u32)

Advance the system clock by clocks master ticks (ares CPU::step), ticking the PPU/APU/coprocessor and HDMA in lockstep. Default no-op for buses whose timebase is charged elsewhere (the SA-1 second CPU) or that don’t model timing (unit-test buses).

fn poll_nmi(&mut self) -> bool

Edge-triggered NMI poll (PPU vblank → CPU). Returns true once per high→low edge.

fn poll_irq(&mut self) -> bool

Level-sensitive IRQ poll (PPU HV-IRQ, on-cart coprocessor, APU timer). Honored only when the CPU’s I flag is clear.

impl Debug for NullBus

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for NullBus

fn default() -> NullBus

Returns the “default value” for a type.