GBDK 2020 Docs  4.2.0
API Documentation for GBDK 2020
Supported Consoles & Cross Compiling

Consoles Supported by GBDK

As of version 4.2.0 GBDK includes support for other consoles in addition to the Game Boy.

  • Game Boy and related clones
    • Nintendo Game Boy / Game Boy Color (GB/GBC)
    • Analogue Pocket (AP)
    • Mega Duck / Cougar Boy (DUCK)
  • Sega Consoles
    • Sega Master System (SMS)
    • Sega Game Gear (GG)
  • NES/Famicom (NES)
  • MSX DOS (MSXDOS) (partial support)

While the GBDK API has many convenience functions that work the same or similar across different consoles, it's important to keep their different capabilities in mind when writing code intended to run on more than one. Some (but not all) of the differences are screen sizes, color capabilities, memory layouts, processor type (z80 vs gbz80/sm83) and speed.

Cross Compiling for Different Consoles


When compiling and building through lcc use the -m<port>:<plat> flag to select the desired console via its port and platform combination. See below for available settings.


When building directly with the sdcc toolchain, the following must be specified manually (when using lcc it will populate these automatically based on -m<port>:<plat>).

When compiling with sdcc:

  • -m<port>, -D__PORT_<port> and -D__TARGET_<plat>

When assembling select the appropriate include path: -I<gbdk-path>lib/<plat>.

The assemblers used are:

When linking:

  • Select the appropriate include paths: -k <gbdk-path>lib/<port>, -k <gbdk-path>lib/<plat>
  • Include the appropriate library files -l <port>.lib, -l <plat>.lib
  • The crt will be under <gbdk-path>lib/<plat>/crt0.o

The linkers used are:

MSXDOS requires an additional build step with makecom after makebin to create the final binary:

  • makecom <image.bin> [<image.noi>] <>

Console Port and Platform Settings

Note: Starting with GBDK-2020 4.1.0 and SDCC 4.2, the Game Boy and related clones use sm83 for the port instead of gbz80

  • Nintendo Game Boy / Game Boy Color
    • lcc : -msm83:gb
    • port:sm83, plat:gb
  • Analogue Pocket
    • lcc : -msm83:ap
    • port:sm83, plat:ap
  • Mega Duck / Cougar Boy
    • lcc : -msm83:duck
    • port:sm83, plat:duck
  • Sega Master System
    • lcc : -mz80:sms
    • port:z80, plat:sms
  • Sega Game Gear
    • lcc : -mz80:gg
    • port:z80, plat:gg
  • NES
    • lcc : -mmos6502:nes
    • port:mos6502, plat:nes
    • lcc : -mz80:msxdos
    • port:z80, plat:msxdos

Cross-Platform Constants

There are several constant #defines that can be used to help select console specific code during compile time (with #ifdef, #ifndef) .

Console Identifiers

  • When <gb/gb.h> is included (either directly or through <gbdk/platform.h>)
    • When building for Game Boy:
      • NINTENDO will be #defined
      • GAMEBOY will be #defined
    • When building for Analogue Pocket
      • NINTENDO will be #defined
      • ANALOGUEPOCKET will be #defined
    • When building for Mega Duck / Cougar Boy
      • NINTENDO will be #defined
      • MEGADUCK will be #defined
  • When <sms/sms.h> is included (either directly or through <gbdk/platform.h>)
    • When building for Master System
      • SEGA will be #defined
      • MASTERSYSTEM will be #defined
    • When building for Game Gear
      • SEGA will be #defined
      • GAMEGEAR will be #defined
  • When <nes/nes.h> is included (either directly or through <gbdk/platform.h>)
    • NINTENDO_NES will be #defined
  • When <msx/msx.h> is included (either directly or through <gbdk/platform.h>)
    • MSXDOS will be #defined

Console Hardware Properties

Constants that describe properties of the console hardware are listed below. Their values will change to reflect the current console target that is being built.

Using <gbdk/...> headers

Some include files under <gbdk/..> are cross platform and others allow the build process to auto-select the correct include file for the current target port and platform (console).

For example, the following can be used

#include <gbdk/platform.h>
#include <gbdk/metasprites.h>

Instead of

#include <gb/gb.h>
#include <gb/metasprites.h>


#include <sms/sms.h>
#include <sms/metasprites.h>

Cross Platform Example Projects

GBDK includes an number of cross platform example projects. These projects show how to write code that can be compiled and run on multiple different consoles (for example Game Boy and Game Gear) with, in some cases, minimal differences.

They also show how to build for multiple target consoles with a single build command and Makefile. The Makefile.targets allows selecting different port and plat settings when calling the build stages.

Cross Platform Asset Example

The cross-platform Logo example project shows how assets can be managed for multiple different console targets together.

In the example utility_png2asset is used to generate assets in the native format for each console at compile-time from separate source PNG images. The Makefile is set to use the source PNG folder which matches the current console being compiled, and the source code uses set_bkg_native_data() to load the assets tiles in native format to the tile memory used for background tiles on that platform.

Hardware Summaries

The specs below reflect the typical configuration of hardware when used with GBDK and is not meant as a complete list of their capabilities.


  • Sprites:
    • 256 tiles (upper 128 are shared with background) (amount is doubled in CGB mode)
    • tile flipping/mirroring: yes
    • 40 total, max 10 per line
    • 2 x 4 color palette (color 0 transparent). 8 x 4 color palettes in CGB mode
  • Background: 256 tiles (typical setup: upper 128 are shared with sprites) (amount is doubled in CGB mode)
    • tile grid size: 8x8
    • tile attribute grid size: 8x8 (CGB mode only)
    • tile flipping/mirroring: no (yes in CGB mode)
    • 1 x 4 color palette. 8 x 4 color palettes in CGB mode
  • Window "layer": available
  • Screen: 160 x 144
  • Hardware Map: 256 x 256


  • Sprites:
    • 256 tiles (a bit less in the default setup)
    • tile flipping/mirroring: no
    • 64 total, max 8 per line
    • 1 x 16 color palette (color 0 transparent)
  • Background: 512 tiles (upper 256 are shared with sprites)
    • tile grid size: 8x8
    • tile attribute grid size: 8x8
    • tile flipping/mirroring: yes
    • 2 x 16 color palettes
  • Window "layer": not available
  • SMS
    • Screen: 256 x 192
    • Hardware Map: 256 x 224
  • GG
    • Screen: 160 x 144
    • Hardware Map: 256 x 224


  • Sprites:
    • 8x8 or 8x16
    • 256 tiles
    • tile flipping/mirroring: yes
    • 64 total, max 8 per line
    • 4 x 4 color palette (color 0 transparent)
  • Background: 256 tiles
    • tile grid size: 8x8
    • tile attribute grid size: 16x16 (bit packed into 32x32)
    • tile flipping/mirroring: no
    • 4 x 4 color palette (color 0 same for all sub-palettes)
  • Window "layer": not available
  • Screen: 256 x 240
  • Hardware Map: Depends on mirroring mode
    • 256 x 240 (single-screen mirroring)
    • 512 x 240 (vertical mirroring / horizontal scrolling)
    • 256 x 480 (horizontal mirroring / vertical scrolling)
    • 512 x 480 (4-screen layout. Requires additional RAM on cartridge)

Safe VRAM / Display Controller Access


  • VRAM / Display Controller (PPU)
    • VRAM and some other display data / registers should only be written to when the STATF_B_BUSY bit of STAT_REG is off. Most GBDK API calls manage this automatically.


  • Display Controller (VDP)
    • Writing to the VDP should not be interrupted while an operation is already in progress (since that will interfere with the internal data pointer causing data to be written to the wrong location).
    • Recommended approach: Avoid writing to the VDP (tiles, map, scrolling, colors, etc) during an interrupt routine (ISR).
    • Alternative (requires careful implementation): Make sure writes to the VDP during an ISR are only performed when the _shadow_OAM_OFF flag indicates it is safe to do so.


Using Game Boy Color (CGB) Features

Differences Versus the Regular Game Boy (DMG/GBP/SGB)

These are some of the main hardware differences between the Regular Game Boy and the Game Boy Color.

  • CPU: Optional 2x Speed mode
  • Serial Link: Additional Speeds 2KB/s, 32KB/s, 64KB/s
  • IR Port
  • Sprites:
    • 2 banks x 256 tile patterns (2x as many) (typically upper 128 of each bank shared with background)
    • 8 x 4 color palettes in CGB mode (BGR-555 per color, 32768 color choices)
  • Background:
    • 2 banks x 256 tile patterns (2x as many) (typically upper 128 of each bank shared with sprites)
    • Second map bank for tile attributes (color, flipping/mirroring, priority, bank)
    • 8 x 4 color palettes in CGB mode (BGR-555 per color, 32,768 color choices))
    • BG and Window master priority
  • WRAM: 8 x 4K WRAM banks in the 0xD000 - 0xDFFF region

CGB features in GBDK

These are some of the main GBDK API features for the CGB. Many of the items listed below link to additional information.

CGB Examples

Several examples in GBDK show how to use CGB features, including the following:

  • gb/colorbar, gb/dscan, cross-platform/large_map, cross-platform/logo, cross-platform/metasprites

Porting Between Supported Consoles

From Game Boy to Analogue Pocket

The Analogue Pocket operating in .pocket mode is (for practical purposes) functionally identical to the Game Boy / Color though it has a couple changes listed below. These are handled automatically in GBDK as long as the practices outlined below are followed.

Official differences:

  • Altered register flag and address definitions
  • Different logo data in the header at address 0x0104:
    • 0x01, 0x10, 0xCE, 0xEF, 0x00, 0x00, 0x44, 0xAA, 0x00, 0x74, 0x00, 0x18, 0x11, 0x95, 0x00, 0x34, 0x00, 0x1A, 0x00, 0xD5, 0x00, 0x22, 0x00, 0x69, 0x6F, 0xF6, 0xF7, 0x73, 0x09, 0x90, 0xE1, 0x10, 0x44, 0x40, 0x9A, 0x90, 0xD5, 0xD0, 0x44, 0x30, 0xA9, 0x21, 0x5D, 0x48, 0x22, 0xE0, 0xF8, 0x60

Observed differences:

  • MBC1 and MBC5 are supported, MBC3 won't save and RTC doesn't progress when game is not running, the HuC3 isn't supported at all (via JoseJX and sg).
  • The Serial Link port does not work
  • The IR port in CGB mode does not work as reliably as the Game Boy Color

In order for software to be easily ported to the Analogue Pocket, or to run on both, use the following practices.

Registers and Flags

Use API defined registers and register flags instead of hardwired ones.

Boot logo

As long as the target console is set during build time then the correct boot logo will be automatically selected.

From Game Boy to SMS/GG

RAM Banks

  • The SMS/GG ROM file size must be at least 64K to enable mapper support for RAM banks in emulators.
    • If the generated ROM is too small then -yo 4 for makebin (or -Wm-yo4 for LCC) can be used to set the size to 64K.

Tile Data and Tile Map loading

Tile and Map Data in 2bpp Game Boy Format

  • set_bkg_data() and set_sprite_data() will load 2bpp tile data in "Game Boy" format on both GB and SMS/GG.
  • On the SMS/GG set_2bpp_palette() sets 4 colors that will be used when loading 2bpp assets with set_bkg_data(). This allows GB assets to be easily colorized without changing the asset format. There is some performance penalty for using the conversion.
  • set_bkg_tiles() loads 1-byte-per-tile tilemaps both for the GB and SMS/GG.

Tile and Map Data in Native Format

Use the following api calls when assets are avaialble in the native format for each platform.


  • GB/AP: loads 2bpp tiles data
  • SMS/GG: loads 4bpp tile data


  • GB/AP: loads 1-byte-per-tile tilemaps
  • SMS/GG: loads 2-byte-per-tile tilemaps

There are also bit-depth specific API calls:

Emulated Game Boy Color map attributes on the SMS/Game Gear

On the Game Boy Color, VBK_REG is used to select between the regular background tile map and the background attribute tile map (for setting tile color palette and other properties).

This behavior is emulated for the SMS/GG when using set_bkg_tiles() and VBK_REG. It allows writing a 1-byte tile map separately from a 1-byte attributes map.

Tile map attributes on SMS/Game Gear use different control bits than the Game Boy Color, so a modified attribute map must be used.

From Game Boy to NES

The NES graphics architecture is similar to the GB's. However, there are a number of design choices in the NES hardware that make the NES a particularly cumbersome platform to develop for, and that will require special attention.

Most notably:

  • PPU memory can only be written in a serial fashion using a data port at 0x2007 (PPUDATA)
  • PPU memory can only be written to during vblank, or when manually disabling rendering via PPUMASK. Hblank writes to PPU memory are not possible
  • PPU memory write address is re-purposed for scrolling coordinates when rendering is enabled which means PPU memory updates / scrolling must cooperate
  • PPU internal palette memory is also mapped to external VRAM area making palette updates during rendering very expensive and error-prone
  • The base NES system has no support for any scanline interrupts. And cartridge mappers that add scanline interrupts do so using wildly varying solutions
  • There's no easy way to determine the current scanline or CPU-to-PPU alignment meaning timed code is often required on the NES
  • The PAL variant of the NES has very different CPU / PPU timings, as do the Dendy clone and other clone systems

To provide an easier experience, gbdk-nes attempts to hide most of these quirks so that in theory the programming experience for gbdk-nes should be as close as possible to that of the GB/GBC. However, to avoid surprises it is recommended to familiarize yourself with the NES-specific quirks and implementation choices mentioned here.

This entire section is written as a guide on porting GB projects to NES. If you are new to GBDK, you may wish to familiarize yourself with using GBDK for GB development first as the topics covered will make a lot more sense after gaining experience with GB development.

Buffered mode vs direct mode

On the GB, the vblank period serves as an optimal time to write data to PPU memory, and PPU memory can also be written efficiently with VRAM DMA.

On the NES, writing PPU memory during the vblank period is not optional. Whenever rendering is turned on the PPU is in a state where accessing PPU memory results in undefined behavior outside the short vblank period. The NES also has no VRAM DMA hardware to help with data writes. This makes the vblank period not only more precious, but important to never exceed to avoid glitched games.

To deal with this limitation, all functions in gbdk-nes that write to PPU memory can run in either Buffered or Direct mode.

The good news is that switching between buffered and direct mode in gbdk-nes is usually done behind-the-scenes and normally shouldn't affect your code too much, as long as you use the portable GBDK functions and macros to do this.

  • DISPLAY_ON / SHOW_BG / SHOW_SPR will all switch the system into buffered mode, allowing limited amounts of transfers during vblank, not the display of graphics
  • DISPLAY_OFF will switch the system into direct mode, allowing much larger/faster transfers while the screen is blanked

The following sections describe how the buffered / direct modes work in more detail. As buffered / direct mode is mostly hidden by the API calls, feel free to skip these sections if you wish.

Buffered mode implementation details

To take maximum advantage of the short vblank period, gbdk-nes implements the same system as nearly every other NES engine: An unrolled loop that pulls prepared data bytes from the stack.


The data structure to facilitate this is usually called a vram transfer buffer, often affectionately called a "popslide" buffer after Damian Yerrick's implementation. This buffer essentially forms a list of commands where each comand sets up a new PPU address and then writes a sequence of bytes with an auto-increment of either +1 or +32. Each such command is often called a "stripe" in the nesdev community.

It starts at 0x100 and takes around half of the hardware stack page. You can think of the transfer buffer as a software-implemented DMA that allows writing bytes at the optimal rate of 8 cycles / byte. (ignoring the PPU address setup cost)

The buffer allows writing up to 32 continuous bytes at a time. This allows updating a full screen row / column, or two 8x8 tiles worth of tile data in one command / "stripe".

By doing writes to this buffer during game logic, your game will effectively keep writing data transfer commands for the vblank NMI handler to process in the next vblank period, without having to wait until the vblank.

Given that transfer buffer only has space for around 100 data bytes, it is important to not overfill the buffer, as this will bring code execution to a screeching halt, until the NMI handler empties the old contents of the buffer to free up space to allow new commands to be written.

Buffered mode is typically used for scrolling updates or dynamically animated tiles, where only a small amount of bytes need updating per frame.

Direct mode implementation details

During direct mode, all graphics routines will write directly to the PPUADDR / PPUDATA ports and the transfer buffer limit is never a concern because the transfer buffer is effectively avoided.

Direct mode is typically used for initializing large amounts of tile data at boot and/or level loading time. Unless you plan to have an animated loading screen and decompress a lot of data, it makes more sense to just fade the screen to black and allow direct mode to write data as fast as possible.

Caveat: Make sure the transfer buffer is emptied before switching to direct mode

Because the switch to the direct mode is instant and doesn't wait for the next invocation of the vblank, it is possible to create situations where there is still remaining data in the transfer buffer that would only get written once the system is switched back to buffered mode.

To avoid this situation, make sure to always "drain" the buffer by doing a call to wait_vbl_done when you expect your code to finish.

Caveat: Only update the PPU palette during buffered mode

The oddity that PPU palette values are accessed through the same mechanism as other PPU memory bytes comes with the side effect that the vblank NMI handler will only write the palette values in buffered mode.

The reason for this design choice is two-fold:

  • Having the NMI handler keep doing the palette updates when in direct mode would result in a race condition when the NMI handler interrupts the direct mode code and messes with the PPUADDR state that the direct mode code expects to remain unchanged
  • Having the palette updates also switch to direct mode would run into another quirk of the system: Pointing PPUADDR at palette registers when display is turned off will make the display output that palette color instead of the common background color. The result would be glitchy artifacts on screen when updating the palette, leading to slightly-glitchy looking game whenever the palette is updated with the screen off

To work around this, you are advised to never fully turn the display off during a palette fade. If you don't follow this advice all your palette updates will get delayed until the screen is turned back on.

Shadow PPU registers

Like the SMS, the NES hardware is designed to only allow loading the full X/Y scroll on the very first scanline. i.e., under normal operation you are only allowed to change the Y-scroll once.

In contrast to the SMS, this limitation can be circumvented with a specific set of out-of-order writes to the PPUSCROLL/PPUADDR registers, taking advantage of the quirk that the PPUADDR and PPUSCROLL share register bits. But this write sequence is very timing-sensitive as the writes need to fall into (a smaller portion of) the hblank period in order to avoid race conditions when the CPU and PPU both try to update the same register during scanline rendering.

To simplify the programming interface, gbdk-nes functions like move_bkg / scroll_bkg only ever update shadow registers in RAM. The vblank NMI handler will later pick these values up and write them to the actual PPU registers registers.

Implementation of (fake) vbl / lcd handlers

GBDK provides an API for installing Interrupt Service Routines that execute on start of vblank (VBL handler), or on a specific scanline (LCD handler).

But the base NES system has no suitable scanline interrupts that can provide such functionality. So instead, gbdk-nes API allows fake handlers to be installed in the goal of keeping code compatible with other platforms.

  • An installed VBL handler will be called immediately when calling wait_vbl_done. This handler should only update PPU shadow registers
  • An installed LCD handler for a specific scanline will be called after the vblank NMI handler has finished execution, and will then manually run a delay loop to reach that scanline before calling your installed LCD handler.

Because the LCD "ISR" is actually implemented with a delay loop, it will burn a lot of CPU cycles in the frame - the further down the scanline is the larger the CPU cycle loss. In practice this makes this faked-LCD-ISR functionality only suited for status bars at the top screen, or simple parallax cutscenes where the CPU has little else to do.

The support for VBL and LCD handlers is currently under consideration and subject to change in newer versions of gbdk-nes.

Caveat: Make sure to call wait_vbl_done on every frame

On the GB, the call to wait_vbl_done is an optional call that serves two purposes:

  1. It provides a consistent frame timing for your game
  2. It allows future register writes to be synchronized to the screen

On gbdk-nes the second point is no longer true, because writes need to be made to the shadow registers before wait_vbl_done is called.

But the wait_vbl_done call serves two other very important purposes:

A. It calls the optional VBL handler, where shadow registers can be written (and will later be picked up by the actual vblank NMI handler) B. It calls flush_shadow_attributes so that updates to background attributes actually get written to PPU memory

For these reasons you should always include a call to wait_vbl_done if you expect to see any graphical updates on the screen.

Tile Data and Tile Map loading

Tile and Map Data in 2bpp Game Boy Format

Tile and Map Data in Native Format

Use the following api calls when assets are avaialble in the native format for each platform.


  • GB/AP: loads 2bpp tiles data
  • NES: loads 2bpp tiles data


  • GB/AP: loads 1-byte-per-tile tilemaps
  • NES: loads 1-byte-per-tile tilemaps

Bit-depth specific API calls:

Platform specific API calls:

Game Boy Color map attributes on the NES

On the Game Boy Color, VBK_REG is used to select between the regular background tile map and the background attribute tile map (for setting tile color palette and other properties).

This behavior of setting VBK_REG to specify tile indices/attributes is not supported on the NES platform. Instead the dedicated functions for attribute setting should be used. These will work on other platforms as well and are the preferred way to set attributes.

To maintain API compatibility with other platforms that have attributes on an 8x8 grid specified with a whole byte per attribute, the NES platform supports the dedicated calls for setting attributes on an 8x8 grid:

This allows code to for attribute setting to remain unchanged between platforms. The effect of using these calls is that some attribute setting will be redundant due to the coarser attribute grid. i.e., setting the attribute at coordinates (4, 4), (4,5), (5, 4) and (5, 5) will all set the same attribute.

There is one more platform specific difference to note: While the set_bkg_attribute_xy() function takes coordinates on a 8x8 grid, the set_bkg_attributes() and set_bkg_submap_attributes() functions take a pointer to data in NES packed attribute format, where each byte contains data for 4 16x16 attribute. i.e. a 32x32 region.

While this implementation detail of how the attribute map is encoded is usually hidden by the API functions it does mean that code which manually tries to read the attribute data is NOT portable between NES/other platforms, and is not recommended.

Tile map attributes on NES are on a 16x16 grid and use different control bits than the Game Boy Color.
  • NES 16x16 Tile Attributes are bit packed into 4 attributes per byte with each 16x16 area of a 32x32 pixel block using the bits as follows:

From Game Boy to Mega Duck / Cougar Boy

The Mega Duck is (for practical purposes) functionally identical to the Original Game Boy though it has a couple changes listed below.

Summary of Hardware changes:

  • Cartridge Boot Logo: not present on Mega Duck
  • Cartridge Header data: not present on Mega Duck
  • Program Entry Point: 0x0000 (on Game Boy: 0x0100 )
  • Display registers and flag definitions: Some changed
  • Audio registers and flag definitions: Some changed
  • MBC ROM bank switching register address: 0x0001 (many Game Boy MBCs use 0x2000 - 0x3FFF)

Best Practices

In order for software to be easily ported to the Mega Duck, or to run on both, use these practices. That will allow GBDK to automatically handle most of the differences (for the exceptions see Sound Register Value Changes).

Sound Register Value Changes

There are two hardware changes which will not be handled automatically when following the practices mentioned above.

These changes may be required when using existing Sound Effects and Music Drivers written for the Game Boy.

  1. Registers NR12_REG, NR22_REG, NR42_REG, and NR43_REG have their contents nybble swapped.
    • To maintain compatibility the value to write (or the value read) can be converted this way: ((uint8_t)(value << 4) | (uint8_t)(value >> 4))
  2. Register NR32_REG has the volume bit values changed.
    • Game Boy: Bits:6..5 : 00 = mute, 01 = 100%, 10 = 50%, 11 = 25%
    • Mega Duck: Bits:6..5 : 00 = mute, 01 = 25%, 10 = 50%, 11 = 100%
    • To maintain compatibility the value to write (or the value read) can be converted this way: (((~(uint8_t)value) + (uint8_t)0x20u) & (uint8_t)0x60u)

Graphics Register Bit Changes

These changes are handled automatically when their GBDK definitions are used.

LCDC_REG Flag Game Boy Mega Duck Purpose
LCDCF_B_ON .7 .7 (same) Bit for LCD On/Off Select
LCDCF_B_WIN9C00 .6 .3 Bit for Window Tile Map Region Select
LCDCF_B_WINON .5 .5 (same) Bit for Window Display On/Off Control
LCDCF_B_BG8000 .4 .4 (same) Bit for BG & Window Tile Data Region Select
LCDCF_B_BG9C00 .3 .2 Bit for BG Tile Map Region Select
LCDCF_B_OBJ16 .2 .1 Bit for Sprites Size Select
LCDCF_B_OBJON .1 .0 Bit for Sprites Display Visible/Hidden Select
LCDCF_B_BGON .0 .6 Bit for Background Display Visible Hidden Select

Detailed Register Address Changes

These changes are handled automatically when their GBDK definitions are used.

Register Game Boy Mega Duck
LCDC_REG 0xFF40 0xFF10
STAT_REG 0xFF41 0xFF11
SCY_REG 0xFF42 0xFF12
SCX_REG 0xFF43 0xFF13
LY_REG 0xFF44 0xFF18
LYC_REG 0xFF45 0xFF19
OBP0_REG 0xFF48 0xFF14
OBP1_REG 0xFF49 0xFF15
WY_REG 0xFF4A 0xFF16
WX_REG 0xFF4B 0xFF17
- - -
NR10_REG 0xFF10 0xFF20
NR11_REG 0xFF11 0xFF22
NR12_REG 0xFF12 0xFF21
NR13_REG 0xFF13 0xFF23
NR14_REG 0xFF14 0xFF24
- - -
NR21_REG 0xFF16 0xFF25
NR22_REG 0xFF17 0xFF27
NR23_REG 0xFF18 0xFF28
NR24_REG 0xFF19 0xFF29
- - -
NR30_REG 0xFF1A 0xFF2A
NR31_REG 0xFF1B 0xFF2B
NR32_REG 0xFF1C 0xFF2C
NR33_REG 0xFF1D 0xFF2E
NR34_REG 0xFF1E 0xFF2D
- - -
NR41_REG 0xFF20 0xFF40
NR42_REG 0xFF21 0xFF42
NR43_REG 0xFF22 0xFF41
NR44_REG 0xFF23 0xFF43
- - -
NR50_REG 0xFF24 0xFF44
NR51_REG 0xFF25 0xFF46
NR52_REG 0xFF26 0xFF45
- - -