The Legend of Zelda graphics and sound (aldonunez/zelda1-disassembly)

When a mode needs the split, the NMI handler waits for the sprite 0 hit under the status bar and then sets the scroll for the room below; while the screen scrolls vertically between rooms it rewrites PPUADDR ($2006) mid-frame instead of PPUSCROLL. zelda-av/sprite-0-split

About: The Legend of Zelda Status bar split

The PPUADDR route is the vertical split the NESdev scrolling page describes (nes-hardware/scroll); a PPUSCROLL write mid-frame changes only the horizontal position.

Cited by: Raster effects, Status bar split

The game keeps 7 DMC samples in three tables of address, length, and rate bytes, and a request byte picks the entry by its lowest set bit. zelda-av/sample-table

About: The Legend of Zelda DPCM samples

{
 "addressBytes": [
  0,
  76,
  128,
  29,
  32,
  40,
  76
 ],
 "lengthBytes": [
  117,
  192,
  64,
  10,
  176,
  144,
  208
 ],
 "rateBytes": [
  15,
  15,
  13,
  15,
  14,
  15,
  14
 ],
 "addresses": [
  "$C000",
  "$D300",
  "$E000",
  "$C740",
  "$C800",
  "$CA00",
  "$D300"
 ],
 "lengths": [
  1873,
  3073,
  1025,
  161,
  2817,
  2305,
  3329
 ]
}

Addresses are $\$C000+64A$ and lengths $16L+1$ bytes (nes-hardware/dmc). Entries 1 and 6 start at the same address with different lengths and rates.

Cited by: DPCM samples

The samples are sound effects; boss code requests $10 for the Aquamentus, Gleeok, and Ganon roar (entry 4, rate $0E), $20 for the Dodongo and Gohma roar (entry 5), and $02 for a boss hit (entry 1), and DeleteSlot requests $08, which the disassembly labels the "hurt" sound (entry 3). zelda-av/sample-effects

About: The Legend of Zelda DPCM samples

{
 "roar": 16,
 "dodongoRoar": 32,
 "bossHit": 2,
 "hurt": 8
}

The effect names are Aldo Nuñez's labels. A request with bit 7 set repeats the sample, as rooms with a boss sound effect do (src/Z_05.asm, BossSoundEffects).

Cited by: DPCM samples

The music driver has Super Mario Bros.' layout; a song entry sets a base into a note-length table, a length code's low 3 bits index it, notes index a table of big-endian 16-bit timer periods, and a square note starts with duty byte $82 and sweep byte $7F, the same register values Super Mario Bros. uses. zelda-av/music-driver

About: The Legend of Zelda Music driver

{
 "dutyByte": 130,
 "sweepByte": 127,
 "lengthCodeBits": 3
}

Shared period values include $02A6, $0280, $025C, $023A, $021A, $01DF, $01C4, and $01AB, all in SMB1's FreqRegLookupTbl. Both games are Nintendo's (1985 and 1986); the code shows a shared design, and who wrote either driver is not sourced here.

Cited by: Music driver