Struct BgSplitState 

pub struct BgSplitState {
    pub nt_addr: u16,
    pub at_addr: u16,
    pub fine_y: u8,
    pub chr_bank: u8,
}

Per-tile override produced by a mapper that implements a vertical split-screen mode (currently MMC5 via $5200-$5202).

MMC5’s split allows a vertical band of the screen to render from an independently scrolled “alt region” backed by ExRAM-as-nametable and a dedicated 4 KiB CHR bank. The PPU consults Mapper::bg_split_state once per 8-dot BG fetch group (at the NT-byte fetch boundary). When Some(...) is returned, the PPU uses the supplied nametable address, attribute address, and fine-Y in place of its own loopy-v derivation for that tile, and the mapper internally latches the CHR bank for the following BG pattern fetches.

Fields

nt_addr: u16

Synthesized nametable byte address in $2000-$3EFF, computed from the alt-region scroll and the current coarse-X.

at_addr: u16

Synthesized attribute byte address in the same nametable.

fine_y: u8

Fine-Y (0..=7) within the alt-region’s logical row.

chr_bank: u8

4 KiB CHR bank index (from $5202 for MMC5) for the alt region’s BG pattern fetches.

Trait Implementations

impl Clone for BgSplitState

fn clone(&self) -> BgSplitState

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for BgSplitState

impl Debug for BgSplitState

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

Formats the value using the given formatter.

impl Eq for BgSplitState

impl PartialEq for BgSplitState

fn eq(&self, other: &BgSplitState) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for BgSplitState