tmerritt
71ada15de0
Pass 3 named the 10 data regions in prg.s, then the project was promoted
out of _wip/ so `make` now proves header + PRG + CHR against the original
ROM instead of only the PRG bank.
Data regions named:
LevelPtrTable $C000-$C03B (60 B) level header data
ObjectPtrTable $C03C-$C043 (8 B) 4 pointer pairs
LevelDataPtrTable $C044-$C79D (1882 B) level data pointers
SpriteInitPtrTable labelled at $C4B0 see residue note
UnreachedCode_D650 $D650-$D696 (71 B) unreached code
UnreachedCode_E144 $E144-$E165 (34 B) unreached code
MusicDataTable $F55B-$FA47 (1261 B) music/sound data
APUDataTable $FAE6-$FB74 (143 B) APU pulse/noise tables
SfxDataTable $FE59-$FFEF (407 B) sound-effect data
VectorTable $FFF6-$FFFF (10 B) padding + NMI/RESET/IRQ
Promotion (per the AGENTS.md checklist):
- git mv "_wip/Donkey Kong (JU)" "Donkey Kong (JU)"
- add copilot/rom.nes -> ../Donkey Kong (JU).nes symlink
- add header.s / chr.s (one-line .incbin of header.bin / chr.bin)
- linker.cfg gains HEADER ($0000/16 B) and CHR ($0000/8 KB)
- Makefile switched from `cmp reconstructed_prg.bin prg.bin` to
`cmp reconstructed.nes rom.nes`
- no _tools path change (this Makefile never referenced _tools/)
and no `make regen` pipeline exists for it
Doc corrections:
- project OVERVIEW.md said Mirroring Vertical; header byte 6 = $00
means Horizontal (the root index was right) — fixed
- root OVERVIEW.md: row 18 now BYTE-IDENTICAL, tier paragraph and
summary table refreshed (they had drifted around the Lunar Pool and
Urban Champion promotions), new per-project detail entry
- counts corrected to 19 top-level / 17 _wip in OVERVIEW.md,
TODO.md and AGENTS.md
Residue recorded rather than guessed:
- Pass 2 is partial: 919 Label_ definitions remain (214 semantic
labels applied); noted in TODO.md so nobody reads the promotion as
full semantic naming
- SpriteInitPtrTable's label sits at $C4B0: the routine at $C807 reads
$C4A7,x/$C4A8,x, but that table starts mid-row and a label there
would split the canonical 16-byte audit-comment line
Verification:
make clean && make -> "Byte-identical ROM verified."
verify_pass1.py -> 19/19 top-level build, Donkey Kong (JU) OK
(6014 instr / 12505 B), all comments canonical
Doc-drift sweep: build tiers, mirroring, and stale status tails
Reconciled the docs against verified reality after the Lunar Pool / Urban
Champion / Donkey Kong (JU) promotions and the 2026-10-19 audit-comment
standardization. No source behaviour changed except the two build fixes below.
Build tier (whole-ROM vs PRG-only)
- AGENTS.md: the 17 `_wip/` projects are real disassemblies at the PRG-build
tier, not "skeletons"; header.s/chr.s/rom.nes are promotion additions;
verify_pass1.py covers the top-level projects.
- Root OVERVIEW.md: `_wip` prose, audit-comment narrative and summary table
refreshed (37.5% figure, SEEDED vs OK wording, re-trace false alarm).
- Promoted projects whose build blocks still claimed `make` emits
`reconstructed_prg.bin` compared to `prg.bin` (Balloon Fight, Baseball,
CIRCUS, Clu Clu Land, Excitebike, NES PowerPad, Pac-Man (USA), Tennis):
now describe the whole-ROM `reconstructed.nes` vs `rom.nes`.
- Lunar Pool / Urban Champion / CIRCUS also had stale `cd "_wip/..."`
build paths and "Promotion" items; retargeted to their top-level folders.
Mirroring (header byte 6 bit 0: 0 = Horizontal, 1 = Vertical)
- Corrected DK Jr. prose "horizontal mirroring (flag 6 = $01)" -> vertical,
and both `_wip/Pac-Man` variant notes "Both use vertical mirroring" ->
horizontal (both are byte-6 = $00).
- Re-audited every project OVERVIEW: 0 rows and 0 prose claims now disagree.
Stale status tails
- Retitled/restatused the `_wip` OVERVIEWs to their real `prg.s` (Golf,
Ice Climber (U), Lode Runner, Millipede, Pac-Man Tengen, Pac-Man (U),
Popeye 0/1, Raid, Raid a2, Hogan's Alley, Mario Bros); Golf's
skeleton-era contents rows and Next Steps corrected.
- Dropped the skeleton-era "## Next Steps (per `PROMPTS.md`)" heading and
the "(from the skeleton)" wording across all project OVERVIEWs.
- Rewrote Lunar Pool / Urban Champion Next Steps (both already Pass 1-3
complete and promoted; their tails still described pending Pass 2 and
promotion); fixed root row 13 (Wild Gunman) and row 20 (Duck Hunt).
Also lands two code fixes carried with this sweep:
- `_wip/Hogan's Alley (JU)`: $E9F1-$E9FD and $EA13-$EA14 reclassified as
data with canonical audit comments (the seeded build had decoded a data
table base as code, breaking the build since 2ae09f7). `make` ->
BYTE-IDENTICAL again; reconstructed_prg.bin/.lbl refreshed.
- `_wip/Pyramid (U)`: `Label_D72E` -> `NMI:` (byte-identical).
Verification:
make (Hogan's Alley, Pyramid) -> BYTE-IDENTICAL, BYTE-IDENTICAL
_tools/verify_pass1.py -> 19/19 build, all canonical,
"No truncated or unfaithful Pass 1"
mirroring audit (rows + prose) -> 0 mismatches
Donkey Kong (JU): complete Pass 2 — all 919 Label_ definitions named
The last non-zero Label_ residue in the repo is now gone. Every one of the
919 address-derived definitions in copilot/prg.s is replaced:
* 319 routine entry points (jsr/jmp targets):
- 102 named from observed behaviour (LoadSpriteInitPointerToZp00 $C807,
CopyVramDataToBuffer $CBDF, CheckSpriteListCollision $D8AD,
UpdateRandomSeed $F4ED, ReadControllers $F50E, UpdateSoundEngine $FA48, ...)
- 217 left as SubC<addr> — honest residue where the body is too
context-dependent to name without guessing (Golf: 108, Mario Bros: 223)
- the 77 already-named entries untouched
* 600 internal branch targets named <Routine>_Block / <Routine>_Block_n in
address order within their owning routine (DK Jr./Balloon Fight convention).
Ownership is control-flow containment, so a loop that physically precedes
its own entry lands correctly (FlushPpuBuffer_Block $F1EC under $F228).
* Two proposal collisions disambiguated by indexing zero-page slot:
UpdateObjectListZp5D/DispatchObjectStateZp5E ($DA16/$DA4C) vs
UpdateObjectListZpAE/DispatchObjectStateZpAF ($E1E9/$E250).
jsr/jmp operands stay numeric (Wild Gunman style); only branch operands are
symbolic. Applied with _tools/pass2.py apply (919 defs + 2,622 refs rewritten,
comments re-aligned); the ROM still rebuilds byte-identically and
verify_pass1.py reports 19/19 canonical with no truncated split.
Docs synced: project OVERVIEW.md gains a Pass 2 Details section, root
OVERVIEW.md rows + conventions, TODO.md section 4 closed. dk_full_map.tsv now
records the complete applied map (its zp rows remain unapplied proposals).
_wip status correction: five false "Pass 2 complete" claims + map audit
The `_wip` tier's "Pass 2 complete" headers counted their draft maps' rows, not
the names actually present in `prg.s`, and described the count of *neutral*
`ZpXX` slots in `locals.inc` as "zero-page semantic aliases". Verified against
the sources and corrected in the root inventory rows, the project OVERVIEWs and
TODO:
project named/total Label_ left drafted map
Pinball (JU) 180 / 681 501 210 rows, 179 applied
Ice Climber (JE) 76 / 973 897 255 rows, 76 applied
Donkey Kong Jr. Math 64 / 1035 971 243 rows, 62 applied
Duck Hunt (JUE) 31 / 472 441 272 rows, 31 applied
Ice Climber (U) 2 / 973 971 none - Pass 2 not started
No `_wip` project is Pass 2 complete. Ice Climber (U) was the worst case: the
2026-10-19 sweep itself restated it "Pass 2 complete" while describing its 971
`Label_` definitions in the same paragraph - a copy-paste from (JE); (U) has no
map file at all.
Drafted maps audited row by row against the committed split: they are not
applicable. 100/243 (DK Jr. Math), 96/255 (Ice Climber (JE)) and 17/210
(Pinball) rows point at addresses that are not instruction boundaries - they
were built against an older code/data split - while most of the rest are
unlabelled boundaries that no operand references, or (Duck Hunt) competing
candidate names for one label (`Label_C2BF` alone carries 205). Rows that are
both insertable and corroborated by control flow: 0 in every map. Recorded as
stale and kept for provenance; Pass 2 here needs a fresh map derived from the
committed split.
Also corrected while verifying:
- Mario Bros entry counts (docs said 252 / 90 + 165 / 477 sites / 156 neutral
slots; the file holds 262 distinct `jsr`/`jmp` targets = 39 semantic + 223
`SubC<addr>`, 478 sites, 151 slots).
- root `_wip` prose line/label ranges (4,482-17,180 lines, 192-971 `Label_`,
11,126 total) and the Ice Climber code figure (74.6% / 6,112 instr, not
74.7% / 6,113).
- TODO §4 re-scoped to the promoted tier, with the `_wip` residue table added.
Verification: `make` across all 17 `_wip` projects -> BYTE-IDENTICAL (17/17);
`_tools/verify_pass1.py` -> 19/19 build, all canonical, "No truncated or
unfaithful Pass 1 found". No source bytes changed.
Balloon Fight (JU): apply locals.inc/symbols.inc names to prg.s (Pass 3)
Substitutes symbol names for 922 numeric operands: 125 hardware registers
(symbols.inc) and 797 of 813 zero-page/RAM operands (locals.inc). The 15
multi-alias addresses were resolved per routine; 16 operands stay numeric
because $13 is used there as a plain high-byte scratch beside Temp12 and
none of its three aliases fits.
- _tools/apply_symbols.py: the substitution tool (dry run by default;
--sites supplies per-routine choices for multi-alias addresses, --report
lists the residue). Only the operand token is rewritten, so the
`; CPU:$.... PRG:.... XX XX` audit comments survive byte for byte.
- prg.s: operand tokens only. make prints "Byte-identical ROM verified."
- OVERVIEW.md (project): instruction quotes now match prg.s, new
alias-reuse table, and section 10 rewritten from the stale "497 Label_"
prose to the real naming state and the 16-site residue.
- OVERVIEW.md (root), TODO.md, AGENTS.md: status, counts, tool list.
verify_pass1.py: 19/19 OK, all audit comments canonical.
Bomberman (U): apply locals.inc/symbols.inc names to prg.s (Pass 3)
Substitutes 362 zero-page operands in copilot/prg.s with the names already
declared in copilot/locals.inc: 354 from single-name addresses and 8 from the
two multi-alias addresses, resolved per site:
$E0/$E1 IndirectPtrLo/Hi in the RAM-clear loop
(InitializeSystemAndRunMainLoop -> Main_WriteSoundDispatchIndex_C317,
which writes $00 across $0100-$07FF via (ptr),y),
SoundDelay0 (the base of the per-channel delay table, indexed by X)
in the sound engine;
No symbols.inc substitution was needed: copilot/prg.s contains no numeric
hardware operands ($2000-$4017) at all. All 362 operands were already written
with two hex digits, so no ca65 `a:` prefix was required.
make -> Byte-identical ROM verified. Operand token only; mnemonics, spacing and
the trailing `; CPU:$.... PRG:.... XX XX` audit comments are untouched.
Remaining numeric operands (758) address bytes that no .inc file names:
505 zero-page (133 addresses), 171 RAM $0100-$07FF (46 addresses) and 82
table reads in $8000+ (54 addresses).
Bomberman (U): substitute 24 in-file table labels at ROM operand sites
Uses the new `--labels` option of `apply_symbols.py` with the
ld65 `-Ln` output (`reconstructed.lbl`). Only labels that prg.s
actually defines and that live in the PRG (+) are considered,
so CHR/header segment labels cannot leak in.
24 numeric operands (`lda ,x`, `adc ,y`, etc.) now read
`lda SystemPaletteData,x`, `adc GameplayObjectClassTable,y`, etc.
All 24 point at exact label addresses; the remaining 58 ROM-space
numeric operands point at interior bytes or unlabelled tables and
stay numeric.
make -> Byte-identical ROM verified.
Bomberman (U): update docs for Pass 3 symbol application
- Project OVERVIEW.md: corrected source file from main.s to prg.s/header.s/chr.s;
output name from reconstructed_bomberman.nes to reconstructed.nes;
rewritten §10 Zero-Page/RAM Symbols table to match locals.inc (with aliases
and unnamed residue documented);
fixed §4 step 1/4 to use IndirectPtrLo/Hi and SoundDelay0 names;
fixed §11 InesHeader location (now header.s);
added §2 Pass 3 summary table;
added §13 notes on legacy main.s and Main_WriteSoundDispatchIndex_C317 misnomer.
- Root OVERVIEW.md §3: updated source line count (7,553), file list, and added
Pass 3 summary.
Both builds verified byte-identical.
Pass 3 symbol application to all 19 top-level projects (2026-10-19)
Ran _tools/apply_symbols.py --write on all 19 promoted projects to substitute
symbolic names from symbols.inc (hardware registers) and locals.inc (zero-page
RAM aliases, forward references) into prg.s operands. The tool preserves the
canonical audit comments (; CPU:$XXXX PRG:XXXX AA BB) and preserves byte
identity — all projects still rebuild byte-identical to their original ROMs.
Per-project operand substitutions:
Baseball (UE) 121 (85 single + 36 hardware)
Tennis (JU) 18 (18 single)
Pac-Man (USA) (Namco) 524 (524 single; 727 multi-alias residues)
CIRCUS 118 (38 single + 80 hardware; 23 multi-alias residues)
Wild Gunman (U) 76 (11 single + 65 hardware)
Joypad Test Cartridge (U) 47 (47 hardware)
NES PowerPad Test Card (U) 89 (89 hardware)
MUSCLE (U) 220 (91 single + 129 hardware)
Lunar Pool (U) 45 (18 single + 27 hardware)
Donkey Kong (JU) 75 (17 single + 58 hardware)
Urban Champion (JU) 70 (4 single + 66 hardware)
Already had symbols applied: Balloon Fight, Bomberman, Burger Time,
Clu Clu Land, Defender 2, Donkey Kong 3, Donkey Kong Jr.
Skipped: Excitebike (JU) — inline prg.s definitions conflict with locals.inc
values and source operands don't match ROM byte encodings; automatic
substitution breaks byte identity.
Documentation updated:
OVERVIEW.md — added Pass 3 symbol notes to all 19 project entries,
added Urban Champion as section #36
TODO.md — current state now reflects complete symbol application across
the promoted tier
Verification: python3 _tools/verify_pass1.py reports all 19 projects OK/SEEDED,
all canonical comments, no truncated or unfaithful Pass 1.
237 lines
14 KiB
Markdown
237 lines
14 KiB
Markdown
# CIRCUS — Game Flow from Power-On
|
||
|
||
This document describes the execution flow of the disassembled CIRCUS PRG bank (16 KB, mapped at CPU **$C000–$FFFF**), starting from power-on. It is based entirely on `copilot/prg.s` in the repository. The rebuild is verified **byte-identical** to the original `prg.bin`.
|
||
|
||
---
|
||
|
||
## 1. ROM and Memory Layout
|
||
|
||
| Property | Value |
|
||
|----------|-------|
|
||
| Format | iNES |
|
||
| PRG | 1 × 16 KB (mapped at CPU $C000–$FFFF) |
|
||
| CHR | 1 × 8 KB |
|
||
| Mirroring | Vertical |
|
||
| PRG bank start | CPU $C000 |
|
||
| Source file | `copilot/prg.s` (~12,755 lines) |
|
||
| Output | `reconstructed.nes` (whole ROM: 16-byte header + 16,384-byte PRG + 8,192-byte CHR) |
|
||
|
||
### Interrupt vectors (CPU $FFFA–$FFFF)
|
||
|
||
| Vector | Address | Handler |
|
||
|--------|---------|---------|
|
||
| NMI | $C05A | `NmiHandler` |
|
||
| RESET | $C000 | `Reset` |
|
||
| IRQ / BRK | $4CB7 | Outside mapped space — effectively unused |
|
||
|
||
---
|
||
|
||
## 2. Build Status
|
||
|
||
`make` in `copilot/` assembles `prg.s` with `ca65`, links with `ld65`, and verifies against `prg.bin`.
|
||
|
||
**Verification result: BYTE-IDENTICAL** — `reconstructed.nes` matches `rom.nes` exactly (header + PRG + CHR).
|
||
|
||
---
|
||
|
||
## 3. Pass Status
|
||
|
||
| Pass | Status | Description |
|
||
|------|--------|-------------|
|
||
| Pass 1 | Complete | Code/data split — entire PRG bank classified as traced code or explicit `.byte` data with `; PRG:$xxxx AA BB` annotations |
|
||
| Pass 2 | Complete | Semantic routine naming — `Label_`/`Sub_` replaced with behavioral names (e.g. `RunMainStateDispatcher`, `UpdateMenuState`, `ReadControllers`); `locals.inc` filled with zero-page aliases (`StateSubstage = $01`, `PpuCtrlShadow = $53`, `WorkPointer0Lo = $7C`, etc.) |
|
||
| Pass 3 | Complete | Data table/structure naming — tables given semantic names (`MainStateHandlerPointerTable`, `MenuTextTable`, `ScreenDescriptorData`, `ObjectStateLookupTables`, `AudioSequenceAndCommandData`, etc.) |
|
||
|
||
---
|
||
|
||
## 4. Reset — CPU $FFFC → $C000
|
||
|
||
**`Reset`** ($C000)
|
||
|
||
On power-on or reset:
|
||
|
||
1. `CLD` — clear decimal mode; `SEI` — disable maskable interrupts.
|
||
2. **Wait for two PPU warm-up vblanks** — `WaitForFirstPpuWarmup` ($C002) and `WaitForSecondPpuWarmup` ($C007) each poll `$2002` bit 7 until clear.
|
||
3. `JSR $C0B8` (`InitializePpuControl`) — write `$08` to PPUCTRL, `$00` to PPUMASK.
|
||
4. `LDX #$FF / TXS` — initialize stack pointer to $FF.
|
||
5. `LDX #$10` — then fall into **`VerifyStackRamPattern`** ($C014): checks stack page bytes `$07EF–$07FF` against `$00` pattern via `TXA / CMP $07EF,X / DEX / BNE`.
|
||
6. **`ClearInternalRamPages`** ($C01F) — clears zero page through `$00FF` via a `STA Zp00,Y / INY / BNE` loop (256 bytes).
|
||
7. **`ClearUpperRamPages`** ($C02D) — clears RAM pages $01–$07 (via indirect store at `$00E0`) and then page $00 with Y=$56, finishing at `$07FF`.
|
||
8. **`InitializeVramQueue`** ($C03F) — clears VRAM queue byte at `$0700`, sets up queue state.
|
||
9. **`InitializeStackPattern`** ($C04D) — writes `$00` to stack page `$07EF–$07FF` via `TXA / STA $07EF,X / DEX / BNE`.
|
||
10. `JSR $C3B8` — early initialization subroutine.
|
||
11. `JMP $C057` (`EnterMainLoop`) — jumps to `jmp $C057` self-loop (effectively idles until NMI drives everything).
|
||
|
||
**Key point:** Like Donkey Kong Jr. in this repo, the main loop is essentially a spin loop; the real-time frame state machine runs inside **NMI**.
|
||
|
||
---
|
||
|
||
## 5. NMI / Frame Heartbeat — `NmiHandler` ($C05A)
|
||
|
||
The NMI fires once per frame and is the central real-time driver:
|
||
|
||
1. **Save registers** (`PHA / TXA / PHA / TYA / PHA`).
|
||
2. Read `PPUSTATUS` ($2002), then check `Zp04` — if nonzero, skip to `ResetPpuScroll` ($C089).
|
||
3. Otherwise: set OAMADDR to 0, trigger OAM DMA via `$4014`, increment `Zp04`, call `$C0B8` (PPU control init), call `$C1B7` (secondary state dispatcher).
|
||
4. Check `NmiDelayCounter` ($FB) — if zero, apply PPU mask shadow; otherwise decrement it.
|
||
5. **`ApplyPpuMaskShadow`** ($C082) — writes `PpuMaskShadow` ($54) to PPUMASK ($2001).
|
||
6. **`FinishNmiPpuUpdates`** ($C084) — decrements `Zp04`.
|
||
7. **`ResetPpuScroll`** ($C089) — latches scroll via `$2002`, writes $00 to $2005 twice, sets PPUCTRL to $7E via `$C0C5`, calls `$F87C` (PPU timing/setup).
|
||
8. **`RunNmiGameLogic`** ($C0A5) — increments `Zp04`, calls `$C402`, `$C0C3`, `$C0D0` (main state dispatcher), decrements `Zp04`.
|
||
9. **`RestoreNmiRegisters`** ($C0B2) — `PLA / TAY / PLA / TAX / PLA / RTI`.
|
||
|
||
PPU control shadow (`PpuCtrlShadow = $53`) and mask shadow (`PpuMaskShadow = $54`) are maintained in zero page and written to the PPU each frame.
|
||
|
||
---
|
||
|
||
## 6. Main State Dispatcher — `RunMainStateDispatcher` ($C0D0)
|
||
|
||
The main game logic is a state machine:
|
||
|
||
1. Increments `ControllerEdgeFlags` ($09), loads `Zp00` (main state index), calls `$C4CD` (indirect call helper).
|
||
2. Dispatches through **`MainStateHandlerPointerTable`** ($C0D7) — 16 word entries pointing to state handlers in the $C000–$C800 range.
|
||
3. States include: initial state dispatch, menu update, round transition, gameplay, title/attract, etc.
|
||
|
||
**`MainStateHandlerPointerTable`** ($C0D7): 16 entries, 2 bytes each (low/high), pointing to handlers such as `$C107`, `$C107`, `$C0E9`, `$C0F9`, `$C007`, `$C01A`, `$C000`, `$C007`, `$C108`, `$C1A6`, `$C1F0`, `$C1D7`, `$C1A5`, `$C10A`, `$C107`, `$C107`.
|
||
|
||
**`SecondaryStateEligibilityTable`** ($C1CC): 9 bytes (`FF FF FF 00 00 01 01 01 01`) controlling which main states allow secondary substage progression.
|
||
|
||
**`SecondaryStateHandlerPointerTable`** ($C1DB): 15 entries pointing to secondary state handlers in $C23A–$C38B range.
|
||
|
||
---
|
||
|
||
## 7. Key Subsystems
|
||
|
||
### Controller Input — `ReadControllers` ($C100)
|
||
Reads controller 1 and 2 via shift-register polling, stores edge flags in `ControllerEdgeFlags` ($09), and maintains shift history at `Controller1Shift` ($E4) / `Controller2Shift` ($E5). Uses **`ControllerBitMaskTable`** ($C4A6: `40 48 60 68`) for bit testing.
|
||
|
||
### Menu System — `UpdateMenuState` ($C21C)
|
||
Handles title/menu state progression. Menu text is stored in **`MenuTextTable`** ($C763) — contains "CONTINUE", "STAGE", "SELECT", "PLAY", "PLAYER", "GAME OVER" strings with control codes ($FF terminators). Menu selection tracked at `MenuSelectionIndex` ($0302).
|
||
|
||
### Palette / Screen Transfer — `SetupScreenPaletteTransfer` ($CD6D)
|
||
Sets up PPU palette and nametable transfers via descriptor streams. Uses **`MenuPaletteData`** ($CCE6), **`MenuScreenParameterTable`** ($CD32), **`ScreenDescriptorPointerTable`** ($CF58), **`ScreenDescriptorData`** ($D0F1), and **`MenuTileData`** ($D724). Palette RAM address set via `SetPaletteRamAddress` ($CA04).
|
||
|
||
### VRAM Updates — `ProcessQueuedVramUpdates` ($D268)
|
||
Processes queued PPU VRAM descriptor commands. Uses **`VramDescriptorPointerTable`** ($D2DD), **`VramDescriptorDispatchTable`** ($D32E), **`VramDescriptorRecords`** ($D3AF). Executed via `ExecuteVramDescriptorStream` ($D330).
|
||
|
||
### Object System — `DispatchVariantObjectUpdate` ($D807)
|
||
Updates variant objects (enemies, items) via a handler pointer table. Uses **`VariantObjectHandlerPointerTable`** ($D80C), **`VariantModeLookupTable`** ($D9B6), **`ObjectMovementParameterPairs`** ($DBD1), and **`ObjectStateLookupTables`** ($DC3F) — a large state-machine table spanning $DC3F–$FE7B with per-object behavior.
|
||
|
||
### Audio — `ProcessAudioFrame` ($F870)
|
||
Per-frame audio engine: `DecodeAudioStream` ($F8D4) and `ExecuteAudioCommand` ($F93E) process audio sequences and commands. Uses **`AudioSequenceAndCommandData`** ($FABB) — a large block at the end of PRG ($FABB–$FFFB) containing audio sequence bytes, command tables, and pitch/period data ($FFC0–$FFFD vectors region). Audio channel state at `AudioChannelStructOffset` ($F4), `AudioSequencePointerLo/Hi` ($F6/$F7).
|
||
|
||
### Initialization
|
||
- **`InitializeApuAndPpu`** ($C399) — APU and PPU initialization.
|
||
- **`InitializeNametablePages`** ($C40F) — clears nametable memory.
|
||
- **`InitializeRoundParameters`** ($D73E) — clears round state, loads variant-dependent gameplay parameters from **`RoundParameterTable`** ($D76D).
|
||
- **`CurrentGameVariant`** ($63) — selects current game variant/mode.
|
||
|
||
---
|
||
|
||
## 8. Zero-Page Aliases (`locals.inc`)
|
||
|
||
| Alias | Address | Role |
|
||
|-------|---------|------|
|
||
| Zp00 | $00 | Main state index / general purpose |
|
||
| StateSubstage | $01 | Secondary state substage |
|
||
| StateTimer | $02 | State timer countdown |
|
||
| Zp04 | $04 | NMI phase / PPU update gate |
|
||
| PpuCtrlShadow | $53 | PPUCTRL shadow register |
|
||
| PpuMaskShadow | $54 | PPUMASK shadow register |
|
||
| CurrentGameVariant | $63 | Current game variant |
|
||
| WorkPointer0Lo | $7C | Indirect pointer 0 low |
|
||
| WorkPointer0Hi | $7D | Indirect pointer 0 high |
|
||
| WorkPointer1Lo | $7E | Indirect pointer 1 low |
|
||
| WorkPointer1Hi | $7F | Indirect pointer 1 high |
|
||
| Controller1Shift | $E4 | Controller 1 shift register |
|
||
| Controller2Shift | $E5 | Controller 2 shift register |
|
||
| AudioChannelStructOffset | $F4 | Audio channel struct offset |
|
||
| AudioSequencePointerLo | $F6 | Audio sequence pointer low |
|
||
| AudioSequencePointerHi | $F7 | Audio sequence pointer high |
|
||
|
||
Full list in `copilot/locals.inc` (161 lines).
|
||
|
||
---
|
||
|
||
## 9. Data Tables (`prg.s`)
|
||
|
||
| Table | Address | Description |
|
||
|-------|---------|-------------|
|
||
| MainStateHandlerPointerTable | $C0D7 | 16-entry main state handler jump table |
|
||
| InitialStateDispatchTailTable | $C0F9 | Initial state dispatch inline code/data |
|
||
| SecondaryStateEligibilityTable | $C1CC | 9-byte secondary state eligibility flags |
|
||
| SecondaryStateHandlerPointerTable | $C1DB | 15-entry secondary state handler table |
|
||
| ControllerBitMaskTable | $C4A6 | Controller bit mask values (`40 48 60 68`) |
|
||
| OamInitializationData | $C549 | OAM initialization byte sequence |
|
||
| SpriteTransferParameterTable | $C564 | OAM DMA transfer setup code |
|
||
| ScreenObjectParameterTable | $C5A6 | Screen object setup parameters |
|
||
| ObjectPositionLookupTable | $C65E | Object position data block |
|
||
| ObjectAttributeLookupTable | $C6C4 | Object attribute data block |
|
||
| GameplayModeParameterTable | $C721 | Gameplay mode parameter block |
|
||
| MenuTextTable | $C763 | Menu strings ("CONTINUE", "STAGE", "SELECT", "PLAY", etc.) |
|
||
| GameplayObjectPointerTable | $C833 | Gameplay object data block |
|
||
| InputDirectionLookupTable | $C906 | Input direction data block |
|
||
| ObjectSlotOffsetTable | $C9F8 | Object slot offset data block |
|
||
| PpuControlMaskTable | $CA47 | PPU control mask values (`C0 80 40 00`) |
|
||
| PpuTimingParameterTable | $CA63 | PPU timing/polling code block |
|
||
| SpriteLayoutTable | $CB51 | Sprite/OAM setup code block |
|
||
| MenuPaletteData | $CCE6 | Menu palette data |
|
||
| MenuScreenParameterTable | $CD32 | Menu screen parameter block |
|
||
| ScreenDescriptorPointerTable | $CF58 | Screen descriptor pointer table |
|
||
| ScreenDescriptorData | $D0F1 | Screen descriptor records |
|
||
| MenuTileData | $D724 | Menu tile descriptor data |
|
||
| RoundParameterTable | $D76D | Round initialization parameters |
|
||
| VariantObjectHandlerPointerTable | $D80C | Variant object handler pointers |
|
||
| VariantModeLookupTable | $D9B6 | Variant mode lookup entries |
|
||
| ObjectMovementParameterPairs | $DBD1 | Object movement parameter pairs |
|
||
| ObjectStateLookupTables | $DC3F | Object state machine tables ($DC3F–$FE7B) |
|
||
| MetaspriteAndObjectFrameData | $D63B | Metasprite/object frame data |
|
||
| GameplayDispatchTable_E4DD | $E4DD | Gameplay dispatch table |
|
||
| GameplayPositionLookup_E51D | $E51D | Gameplay position lookup |
|
||
| GameplayHandlerTable_E52D | $E52D | Gameplay handler table |
|
||
| GameplayParameterTable_E640 | $E640 | Gameplay parameter block |
|
||
| GameplayParameterTable_E6A0 | $E6A0 | Gameplay parameter block |
|
||
| GameplayObjectDescriptorData_E6DF | $E6DF | Gameplay object descriptor data |
|
||
| GameplayDispatchTable_E7E5 | $E7E5 | Gameplay dispatch table |
|
||
| GameplayParameterTable_E96E | $E96E | Gameplay parameter block |
|
||
| GameplayParameterTable_E9B6 | $E9B6 | Gameplay parameter block |
|
||
| GameplayDispatchTable_E9D9 | $E9D9 | Gameplay dispatch table |
|
||
| GameplayLookupTable_EA76 | $EA76 | Gameplay lookup table |
|
||
| GameplayLookupTable_EBC4 | $EBC4 | Gameplay lookup table |
|
||
| GameplayModeTable_EC15 | $EC15 | Gameplay mode table |
|
||
| GameplayInitializationTable_EC21 | $EC21 | Gameplay initialization table |
|
||
| GameplayLookupTable_EDFB | $EDFB | Gameplay lookup table |
|
||
| MovementStepTable | $F226 | Movement step values |
|
||
| MovementCurveTable | $F320 | Movement curve values |
|
||
| AudioVoiceParameterTable | $F023 | Audio voice parameter table |
|
||
| AudioObjectOffsetTable | $F12E | Audio object offset table |
|
||
| AudioGameplaySupportData | $F163 | Audio gameplay support data |
|
||
| SoundRequestTable | $F76C | Sound request table |
|
||
| AudioChannelInitializationTable | $F878 | Audio channel init data |
|
||
| AudioSequenceAndCommandData | $FABB | Audio sequences and commands ($FABB–$FFFB) |
|
||
|
||
---
|
||
|
||
## 10. Build
|
||
|
||
```bash
|
||
cd "CIRCUS/copilot"
|
||
make # → ca65 + ld65 + cmp reconstructed.nes rom.nes → "Byte-identical ROM verified."
|
||
```
|
||
|
||
---
|
||
|
||
## 11. Notes
|
||
|
||
- The main loop (`EnterMainLoop` at $C057) is a self-jump spin loop; all per-frame work is driven by NMI.
|
||
- The IRQ vector ($4CB7) points outside mapped PRG space and is never used.
|
||
- `MenuTextTable` at $C763 contains the visible menu strings ("CONTINUE", "STAGE", "SELECT", "PLAY", "PLAYER", "GAME OVER") interleaved with control codes.
|
||
- `AudioSequenceAndCommandData` at $FABB occupies the final ~300 bytes of PRG and includes the vector-page tail at $FFFA–$FFFB (`C0 00 C0 B7 4C` = NMI vector $C000? No — the vectors at $FFFA are `C0 00` (NMI=$C000?), `C0 B7` ... wait, the actual vectors are at $FFFA-$FFFB in the file. Let me check: line 12754 shows `.byte $C0, $00, $C0, $B7, $4C` at CPU:$FFFB PRG:3FFB. The actual 6502 vectors are at the very end: NMI vector at $FFFA, RESET at $FFFC, IRQ at $FFFE.)
|
||
|
||
---
|
||
|
||
## 12. Next Steps
|
||
|
||
- **Promotion** — move to a top-level `CIRCUS/` folder, add `header.s` / `chr.s` + full-ROM `make` target (as e.g. `Burger Time (U)`), then join the root `OVERVIEW.md` numbered inventory.
|
||
- Optional deeper semantic work: decode `ObjectStateLookupTables` sub-structures, name audio command opcodes in `AudioSequenceAndCommandData`, document variant object behaviors.
|