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feat(cartridge): add 512-byte and 8 KiB serial EEPROM saves

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Select them with --save-type eeprom512 or eeprom8k. The part follows GBATEK's
protocol on Game Pak data bit 0: DMA3 sends one bit per halfword, '11' +
address + '0' requests a 64-bit block that reads back after four dummy bits,
and '10' + address + data + '0' writes one. A write reports busy for a nominal
108,368 cycles before the block is stored. 8 KiB parts decode the low 10
address bits. ROMs above 16 MiB map EEPROM only at 0x0dffff00..0x0dffffff.

Bits shift out only inside machine steps, so failed steps roll back. CPU
stores, byte/word accesses, CPU reads during a read-out, and malformed or
overlapping requests are diagnostics. Blocks are stored first-bit-as-MSB,
matching common .sav layouts, and work with save files and save states.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HhfHfHEuzv2AUTd6erW1gU
This commit is contained in:
0xrsydn 2026-10-14 12:06:17 +07:00
commit 652ea397f2
15 changed files with 828 additions and 24 deletions
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2
crates/desktop/tests/rom_cli.rs
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@ -383,7 +383,7 @@ fn explicit_flash_selection_runs_ram_byte_reader_and_leaves_files_unchanged() {
fn invalid_save_type_options_fail_before_file_access() {
for extra in [
vec!["--save-type"],
vec!["--save-type", "eeprom"],
vec!["--save-type", "fram"],
vec!["--save-type", ""],
vec!["--save-type", "flash128", "--save-type", "flash64"],
] {