Save System

Flash sector layout, SaveBlock structures, and save/load mechanics.

pokeemerald saves to a 128 KB flash chip organized as 32 sectors of 4 KB each. The save system rotates between two save slots for corruption protection and stores trainer data, bag contents, Pokémon party, PC storage, Hall of Fame records, and more.

Flash layout

The 32 sectors are divided into fixed-purpose regions. Sector numbers are defined in include/save.h.

Sector(s)	Constant	Contents
0	SECTOR_ID_SAVEBLOCK2	SaveBlock2 — trainer info, options, Pokédex
1–4	SECTOR_ID_SAVEBLOCK1_START – SECTOR_ID_SAVEBLOCK1_END	SaveBlock1 — current map, bag, money, etc.
5–13	SECTOR_ID_PKMN_STORAGE_START – SECTOR_ID_PKMN_STORAGE_END	PC Pokémon storage (boxes 1–9)
14–27	(Save Slot 2 mirror of 0–13)	Alternating save slot for corruption recovery
28–29	SECTOR_ID_HOF_1 / SECTOR_ID_HOF_2	Hall of Fame records
30	SECTOR_ID_TRAINER_HILL	Trainer Hill data
31	SECTOR_ID_RECORDED_BATTLE	Recorded Battle data

SECTORS_COUNT = 32; NUM_SECTORS_PER_SLOT = 14.

Sector structure

Each 4 KB sector is split into a data region and a footer:

struct SaveSector
{
    u8  data[SECTOR_DATA_SIZE];          // 3968 bytes of save data
    u8  unused[SECTOR_FOOTER_SIZE - 12]; // unused footer padding
    u16 id;                              // sector identifier
    u16 checksum;                        // XOR checksum of data
    u32 signature;                       // must equal SECTOR_SIGNATURE
    u32 counter;                         // incremented on each write
}; // total: SECTOR_SIZE (0x1000 = 4096 bytes)

Key constants from include/save.h:

Constant	Value	Meaning
SECTOR_DATA_SIZE	3968	Usable data bytes per sector
SECTOR_FOOTER_SIZE	128	Footer size in bytes
SECTOR_SIGNATURE	0x8012025	Magic number that marks a valid sector
NUM_SAVE_SLOTS	2	Number of alternating save slots

The game uses approximately 96% of available flash capacity. SaveBlock1 has roughly 84 bytes of headroom and SaveBlock2 has roughly 120 bytes before you must reorganize the sector layout.

Dual-slot rotation

NUM_SAVE_SLOTS = 2. Sectors 0–13 are Save Slot 1 and sectors 14–27 are Save Slot 2. On every normal save the game writes to the slot with the lower counter value. If a write is interrupted the other slot still holds a valid copy, preventing total save loss.

// Save Slot 1: sectors  0-13
// Save Slot 2: sectors 14-27
#define NUM_SECTORS_PER_SLOT 14

Save types

enum
{
    SAVE_NORMAL,                    // standard in-game save
    SAVE_LINK,                      // Link / Battle Frontier save
    SAVE_EREADER,                   // deprecated in Emerald
    SAVE_HALL_OF_FAME,              // writes HOF sectors only
    SAVE_OVERWRITE_DIFFERENT_FILE,  // overwrites without slot check
    SAVE_HALL_OF_FAME_ERASE_BEFORE  // unused
};

Save status codes

Constant	Value	Meaning
SAVE_STATUS_EMPTY	0	No save data found
SAVE_STATUS_OK	1	Save loaded successfully
SAVE_STATUS_CORRUPT	2	Checksum or signature mismatch
SAVE_STATUS_NO_FLASH	4	Flash chip not detected
SAVE_STATUS_ERROR	0xFF	Unrecoverable error

The current status is stored in gSaveFileStatus (extern u16 gSaveFileStatus).

Key functions

Function	Signature	Description
TrySavingData	u8 TrySavingData(u8 saveType)	Attempts a full save; returns SAVE_STATUS_*
LoadGameSave	u8 LoadGameSave(u8 saveType)	Reads save data from flash into RAM
HandleSavingData	u8 HandleSavingData(u8 saveType)	Lower-level save dispatcher
WriteSaveBlock2	bool8 WriteSaveBlock2(void)	Writes only the SaveBlock2 sector
WriteSaveBlock1Sector	bool8 WriteSaveBlock1Sector(void)	Writes one sector of SaveBlock1 incrementally
ClearSaveData	void ClearSaveData(void)	Erases all save sectors
TryReadSpecialSaveSector	u32 TryReadSpecialSaveSector(u8 sector, u8 *dst)	Reads HOF / Trainer Hill / Recorded Battle sectors
TryWriteSpecialSaveSector	u32 TryWriteSpecialSaveSector(u8 sector, u8 *src)	Writes to a special sector

Link save

For link-cable trades and the Battle Frontier, SaveBlock1 is written incrementally across multiple frames using a task:

bool8 LinkFullSave_Init(void);
bool8 LinkFullSave_WriteSector(void);
bool8 LinkFullSave_ReplaceLastSector(void);
bool8 LinkFullSave_SetLastSectorSignature(void);
void  Task_LinkFullSave(u8 taskId);

Do not expand SaveBlock1 or SaveBlock2 beyond their headroom without updating gRamSaveSectorLocations and auditing every sector’s size field. Exceeding SECTOR_DATA_SIZE (3968 bytes) per sector silently truncates data.