Port Number: 000D
Function: Power control
This port enables power to various parts of the ASIC. Each region reads as 0 when unpowered.
USB controller power. Resets when unpowered. Returning to the OS without reinitializing causes it to freeze while USB is connected.
LCD controller power. Resets when unpowered. The LCD does not update until the controller is initialized properly.
Power for RAM range D20000-D3FFFF. When unpowered, its content is quickly randomized.
Power for VRAM range D40000-D7FFFF. When unpowered, its content is quickly randomized.
Writes have no effect. These bits read as 1 if the subsystems controlled by the corresponding bits in 0-3 are receiving power. There is a slight delay between changing bits 0-3 & these changing in response.