Emulando la Gameboy en Rust

What happens from when the emulator starts up?

On each step, the following actions happen:

1. OAM DMA Transfer - Checking if there’s a pending DMA transfer in register 0xFF46

The PPU (screen) has an Object Attribute Memory (OAM) located at 0xFE00-0xFE9F that stores sprite data. The recommended way to update the OAM is using DMA (Direct Memory Access). See pandocs

When you write to register 0xFF46, you’re telling the Game Boy to copy 160 bytes of sprite data into OAM. Here’s how it works:

The register stores a “page” (high byte) of a memory address:

• Writing 0xC1 to 0xFF46 means “copy from address 0xC100”
• The address is constructed by shifting the page value: (page as u16) << 8
• Example: 0xC1 << 8 = 0xC100

Quick mental model:

• Register value 0xXX → copies from 0xXX00 to 0xXX9F (160 bytes)
• Always copies TO: 0xFE00-0xFE9F (OAM)
• Always copies FROM: 0xXX00-0xXX9F (where XX is what you wrote to 0xFF46)

Why only the high byte? Since we always copy exactly 160 bytes and the destination is always OAM, we only need to specify where to copy FROM. The low byte is always 0x00 (start of the page), making it simple to just write one byte.

More info on OAM DMA Transfer

2. WIP