pub static MASK_WRITE_DELAY: AtomicU8Expand description
v2.0 Phase 6 (mc-ppu-subpos): the analog $2001 PPUMASK write delay.
In PPU dots. TriCNES applies a $2001 write 2-3 dots after the CPU write
(PPU_Update2001Delay, sub-dot alignment dependent); this emulator’s reload
sits one dot later than that plus the existing 1-dot render gate, so the
effective default is 4. Runtime-tunable (an atomic) so the exact phase can be
swept against the BG Serial In / Stale BG Shift keys without rebuilding.
The mc-ppu-subpos name in the lines above is the v2.0 Phase 6 WORKSTREAM,
not a cargo feature: no manifest declares one, and the read at the BG-reload
freeze below is unconditional. Kept as the historical label rather than
rewritten, but do not go looking for a flag to turn on.