DMA

RP2A03 has two forms of DMA:

• OAM DMA - used for filling PPU OAM with data from CPU memory.
• DMC DMA - used by the APU DMC channel to load the next byte of the sample. Takes priority over OAM DMA.

These operate by pulling the RDY pin of the 6502 CPU core low (which causes it to repeat read cycles indefinitely), and then disconnecting the 6502 from the address bus.