Struct Channel 

pub struct Channel {
    pub dmap: u8,
    pub target: u8,
    pub source_addr: u16,
    pub source_bank: u8,
    pub count_or_indirect: u16,
    pub indirect_bank: u8,
    pub hdma_addr: u16,
    pub line_counter: u8,
    pub scratch: u8,
    pub hdma_completed: bool,
    pub hdma_do_transfer: bool,
}

One of the 8 DMA channels ($43n0-$43nA).

Fields

dmap: u8

$43n0 DMAP — transfer params: bit7 direction (0 = A→B, 1 = B→A), bit6 indirect (HDMA), bit4 reverse (GP-DMA addr decrement), bit3 fixed (GP-DMA addr no-change), bits2-0 mode.

target: u8

$43n1 BBAD — B-bus target low byte (the $21xx register).

source_addr: u16

$43n2-3 A1T — A-bus source address (GP) / table address (HDMA).

source_bank: u8

$43n4 A1B — A-bus source bank.

count_or_indirect: u16

$43n5-6 DAS — GP byte count / HDMA indirect address.

indirect_bank: u8

$43n7 DASB — HDMA indirect bank.

hdma_addr: u16

$43n8-9 A2A — HDMA table running address.

line_counter: u8

$43nA NTRL — HDMA line counter (bit7 = repeat, bits0-6 = lines).

scratch: u8

The undocumented readable scratch latch at $43xB, mirrored at $43xF.

Nothing in the DMA controller reads it — it is a byte of storage the hardware exposes and then forgets about. It matters because it is CPU-visible: AccuracySNES D1.10 writes it and reads it back, snes9x passes that test, and RustySNES returned 0 from both addresses until the test was written.

Deliberately not in the save state, and reset to 0 on load. ares and bsnes do serialise theirs, but adding a byte to the DMA0 section changes its length, and this format’s compatibility rules make that a version-bump decision rather than a free one (docs/adr/0006). The latch has no effect on emulation, so the only cost is that a $43xB read after a load returns 0 instead of the saved byte. Resetting matters more than the omission does: inheriting the pre-load value would make that read depend on what ran before the load, which the determinism contract rules out. Recorded in docs/accuracysnes-plan.md so it stays a decision rather than an oversight.

hdma_completed: bool

HDMA: this channel has finished its table for the frame.

hdma_do_transfer: bool

HDMA: perform a transfer on this line (vs. just decrement the counter).

Trait Implementations

impl Clone for Channel

fn clone(&self) -> Channel

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Channel

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

Formats the value using the given formatter.

impl Default for Channel

fn default() -> Self

Returns the “default value” for a type.

impl Copy for Channel