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feat(cartridge): implement RTC calendar transfers and clock updates

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0xrsydn 2026-10-07 05:55:31 +07:00
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docs/research/emerald-reset.md
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@ -65,17 +65,19 @@ The send register supports 16-bit data; receive latches do not become invented p
See [the register model and evidence limits](../hardware/serial.md#disconnected-multiplayer-configuration).
Multiplayer configuration then reached a Game Pak GPIO control write (`0x080000c8`, PC `0x082e29f8`).
The optional [cartridge GPIO/RTC interface](../hardware/cartridge-gpio.md) now supports read enable, directions, pin latches, and RTC control transactions.
Select it explicitly with `--rtc`; ordinary ROM bytes and other ROMs' default hardware remain unchanged.
No host date, RTC calendar, or successful calendar read is invented.
The optional [cartridge GPIO/RTC interface](../hardware/cartridge-gpio.md) first added read enable, directions, pin latches, and RTC control transactions.
That reached a calendar-read command at PC `0x082e28a6`.
The calendar model now supports date/time reads, complete writes, reset, and caller-supplied elapsed seconds.
Core tests inject deterministic time. Desktop `--rtc` uses UTC startup and monotonic elapsed time, including during GBA STOP.
Select it explicitly; ordinary ROM bytes and other ROMs' default hardware remain unchanged.
Both terminal and native runs with `--rtc` now reach a calendar-read command:
Both terminal and native runs with `--rtc` now reach a Flash unlock write:
```text
Steps: 957729; instructions: 955049; IRQ entries: 80; DMA units: 2600; HALT idle: 0
Nominal cycles: 3520685
PC=0x082e28a6
unsupported RTC calendar access: write 0x07 at 0x080000c4
Steps: 964375; instructions: 961679; IRQ entries: 80; DMA units: 2616; HALT idle: 0
Nominal cycles: 3546961
PC=0x082e1892
unmapped memory at 0x0e005555
```
The native run captures twelve startup frames. These do not establish a working title screen or gameplay.
@ -90,9 +92,10 @@ Workspace debug/release tests, strict Clippy, public ARM/Thumb/memory/BIOS check
Native ROM-window tests and graphics smoke modes pass on Darwin arm64.
The pinned Pong debug/release reports match.
The next requirement is RTC calendar transfers with an explicit clock-source model.
Implement validated date/time formats, read snapshots, writes/reset, and clock ownership without putting host time in the core.
Keep battery persistence and cartridge IRQ behavior explicit; do not equate GBA STOP with stopping a battery-powered RTC.
The next requirement is a cartridge Flash save device, beginning with command unlock and identification.
The failing state contains value `0xaa` and address `0x0e005555`, matching the documented unlock sequence.
Research device selection, IDs, banking, program/erase, busy behavior, and safe persistence before claiming save compatibility.
RTC persistence and cartridge IRQ behavior remain separate missing features.
Ordinary ROM writes remain read-only. Without `--rtc`, the earlier GPIO diagnostic is still expected.
This result does not establish gameplay, linked transfers, or cartridge/serial GPIO interrupt support.
@ -104,3 +107,5 @@ Do not treat digital-level tests as audible-game validation or suppress remainin
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.
[GBATEK backup Flash](https://problemkaputt.de/gbatek-gba-cart-backup-flash-rom.htm) identifies the `0xaa`/`0x5555` unlock and chip-identification sequence.
The bounded failure establishes an access requirement, not the device's capacity or full save compatibility.