63 lines
3.6 KiB
Markdown
63 lines
3.6 KiB
Markdown
# Local Emerald startup: device reset
|
|
|
|
## Initial failure
|
|
|
|
A user-supplied local Emerald ROM stopped in the original BIOS replacement during `RegisterRamReset(0xff)`.
|
|
The BIOS deliberately rejected serial/sound flags and executed `INVALID_ARGUMENT_TRAP` (`0xe7f000f1`).
|
|
This was an unsupported service argument, not an ARM instruction-decoder failure.
|
|
No ROM bytes, extracted code, or assets were added to the repository.
|
|
|
|
## General correction
|
|
|
|
The reset correction introduced bounded sound and [disconnected serial](../hardware/serial.md) initialization models.
|
|
The [sound model](../hardware/audio.md) now also supports Direct Sound, bounded FIFO DMA, and nominal pulse channel 1 playback.
|
|
The BIOS performs reset through original ARM stores against that model.
|
|
Bit 5 selects general-purpose input pins and clears supported serial reset registers.
|
|
Bit 6 disables sound, resets FIFO queues, clears mixing configuration and accessible wave RAM, and sets the functional bias default.
|
|
The low halfword of SIODATA32 is cleared unconditionally, matching the documented BIOS side effect.
|
|
|
|
This is not a game-specific bypass. Original ARM and Thumb callers exercise selected flags and the all-device request.
|
|
Tests verify caller preservation, RAM selection, unselected device state, readback masks, and rejected device activity.
|
|
Byte, halfword, word, block-store, and DMA validation retain explicit errors without partial register writes.
|
|
|
|
## Reproduction and current result
|
|
|
|
Use a local ROM that you may lawfully use:
|
|
|
|
```sh
|
|
direnv exec . cargo run --locked --release -- --rom roms/pokemon-emerald.gba --steps 1000000
|
|
direnv exec . cargo run --locked --release -- --rom roms/pokemon-emerald.gba --window --frames 120
|
|
```
|
|
|
|
The earlier reset-only implementation stopped at master sound enable (`0x04000084`, PC `0x082e0518`).
|
|
The Direct Sound increment then reached a PSG channel 1 trigger (`0x04000065`, PC `0x082e03bc`).
|
|
After implementing channel 1, both runs pass that trigger and stop at channel 2:
|
|
|
|
```text
|
|
Steps: 321161; instructions: 320649; IRQ entries: 0; DMA units: 512; HALT idle: 0
|
|
Nominal cycles: 1038742
|
|
PC=0x082e03c0
|
|
unsupported PSG channel trigger (synthesis not implemented): write 0x80 at 0x0400006d
|
|
```
|
|
|
|
The native run captures three startup frames. Audio-device behavior is validated by original tests, not by audible game output.
|
|
|
|
The native run captures startup frames before this diagnostic. These are not evidence of a working title screen or gameplay.
|
|
The window run does not reach its requested frame limit and correctly exits with failure.
|
|
Terminal execution is also diagnostic, not a compatibility pass.
|
|
Results apply to this local file; no cartridge revision or checksum was inferred from its filename.
|
|
|
|
## Validation and next requirement
|
|
|
|
Workspace debug/release tests, strict Clippy, public ARM/Thumb/memory/BIOS checkpoints, and pinned Pong scenarios pass.
|
|
Native ROM-window tests and graphics smoke modes pass on Darwin arm64.
|
|
The pinned Pong debug/release reports match.
|
|
|
|
The next observed startup requirement is PSG pulse channel 2, which has no sweep unit.
|
|
Channel 1 now has nominal waveform, length, envelope, sweep, and stereo mixing behavior.
|
|
Direct Sound has FIFO clocks and nominal DMA requests. Both use the instantaneous digital-level inspection interface.
|
|
A continuous sample stream and desktop output are still missing. Do not treat digital-level tests as audible-game validation.
|
|
Do not suppress the PSG trigger diagnostic without implementing the requested device behavior.
|
|
Cartridge saves remain a separate required feature. SRAM alone will not support Emerald's Flash save protocol.
|
|
|
|
Hardware and emulator references are recorded in the linked subsystem documents.
|