gba/book/src-bak/09-sram.md

Save RAM (SRAM)

• Address Span: 0xE00_0000 to 0xE00FFFF (64k)

The actual amount of SRAM available depends on your game pak, and the 64k figure is simply the maximum possible. A particular game pak might have less, and an emulator will likely let you have all 64k if you want.

As with other portions of the address space, SRAM has some number of wait cycles per use. As with ROM, you can change the wait cycle settings via the WAITCNT register if the defaults don't work well for your game pak. See the ROM section for full details of how the WAITCNT register works.

The game pak SRAM also has only an 8-bit bus, so have fun with that.

The GBA Direct Memory Access (DMA) unit cannot access SRAM.

Also, you should not write to SRAM with code executing from ROM. Instead, you should move the code to WRAM and execute the save code from there. We'll cover how to handle that eventually.