gbz80.js

const gameboy_hardware_constants = {
  _HW: {
    description: 'Start of the hardware IO registers.',
    value: '$FF00->$FF80',
  },
  _VRAM: {
    description: 'VRAM Memory',
    value: '$8000->$9FFF',
  },
  _SCRN0: {
    description: 'Background 0 Memory',
    value: '$9800->$9BFF',
  },
  _SCRN1: {
    description: 'Background 1 Memory',
    value: '$9C00->$9FFF',
  },
  _SRAM: {
    description: 'Card SRAM',
    value: '$A000->$BFFF',
  },
  _RAM: {
    description: 'WRAM Memory',
    value: '$C000->$DFFF',
  },
  _OAMRAM: {
    description: 'OAM Memory',
    value: '$FE00->$FE9F',

    flags: {
      OAMF_PRI: {
        value: '%10000000',
        description:
          'Flag to set on OAM attribute byte to make the background colors 1-3 to have priority over the sprite.',
      },
      OAMF_YFLIP: {
        value: '%01000000',
        description: 'Flag to set on OAM attribute byte to make the sprite flip in the Y direction',
      },
      OAMF_XFLIP: {
        value: '%00100000',
        description: 'Flag to set on OAM attribute byte to make the sprite flip in the X direction',
      },
      OAMF_PAL0: {
        value: '%00000000',
        description: 'Flag to set on OAM attribute byte to make the sprite use OBP0 in DMG (non-color) mode.',
      },
      OAMF_PAL1: {
        value: '%00010000',
        description: 'Flag to set on OAM attribute byte to make the sprite use OBP1 in DMG (non-color) mode.',
      },
      OAMF_BANK0: {
        value: '%00000000',
        description: 'Flag to set on OAM attribute byte to use a sprite graphics from VRAM Bank 0 in GBC mode.',
      },
      OAMF_BANK1: {
        value: '%00001000',
        description: 'Flag to set on OAM attribute byte to use a sprite graphics from VRAM Bank 1 in GBC mode.',
      },
      OAMF_PALMASK: {
        value: '%00000111',
        description: 'Mask of the color sprite palette index in the OAM attribute byte. In GBC mode.',
      },

      OAMB_PRI: {
        value: '7',
        description:
          'Bit number to set on OAM attribute byte to make the background colors 1-3 to have priority over the sprite.',
      },
      OAMB_YFLIP: {
        value: '6',
        description: 'Bit number to set on OAM attribute byte to make the sprite flip in the Y direction.',
      },
      OAMB_XFLIP: {
        value: '5',
        description: 'Bit number to set on OAM attribute byte to make the sprite flip in the X direction.',
      },
      OAMB_PAL1: {
        value: '4',
        description: 'Bit number to set on OAM attribute byte to make the sprite use OBP1 in DMG (non-color) mode.',
      },
      OAMB_BANK1: {
        value: '3',
        description: 'Bit number to set on OAM attribute byte to use a sprite graphics from VRAM Bank 1 in GBC mode.',
      },
    },
  },
  _AUD3WAVERAM: {
    description: 'WAVE Channel Memory',
    value: '$FF30->$FF3F',
  },
  _HRAM: {
    description: 'HRAM Memory',
    value: '$FF80->$FFFE',
  },

  // MBC5 related, ignored.
  //"rRAMG": { description: "$0000 ; $0000->$1fff
  //"rROMB0": { description: "$2000 ; $2000->$2fff
  //"rROMB1": { description: "$3000 ; $3000->$3fff - If more than 256 ROM banks are present.
  //"rRAMB": { description: "$4000 ; $4000->$5fff - Bit 3 enables rumble (if present)

  // IO Registers
  rP1: {
    description: 'Register for reading joy pad info. (R/W)',
    value: '$FF00',
    flags: {
      P1F_5: {
        value: '%00100000',
        description: 'P15 out port, set to 0 to get buttons',
      },
      P1F_4: {
        value: '%00010000',
        description: 'P14 out port, set to 0 to get dpad',
      },
      P1F_3: { value: '%00001000', description: 'P13 in port' },
      P1F_2: { value: '%00000100', description: 'P12 in port' },
      P1F_1: { value: '%00000010', description: 'P11 in port' },
      P1F_0: { value: '%00000001', description: 'P10 in port' },

      P1F_GET_DPAD: {
        description: 'Value to load in rP1 to enable the reading of the DPad inputs.',
      },
      P1F_GET_BTN: {
        description: 'Value to load in rP1 to enable the reading of the A/B/Start/Select inputs.',
      },
      P1F_GET_NONE: {
        description: 'Value to load in rP1 to disable the reading of input buttons.',
      },
    },
  },

  rSB: {
    description: 'Serial Transfer Data (R/W)',
    value: '$FF01',
  },
  rSC: {
    description: 'Serial I/O Control (R/W)',
    value: '$FF02',
  },

  rDIV: {
    description:
      'Divider register (R/W)\nIncremented at 16384Hz or 32768Hz depending on the CPU speed.\nWrite any value to reset to zero.',
    value: '$FF04',
  },

  rTIMA: {
    description: 'Timer counter (R/W)',
    value: '$FF05',
  },

  rTMA: {
    description: 'Timer modulo (R/W)',
    value: '$FF06',
  },

  rTAC: {
    description: 'Timer control (R/W)',
    value: '$FF07',
    flags: {
      TACF_START: { value: '%00000100' },
      TACF_STOP: { value: '%00000000' },
      TACF_4KHZ: { value: '%00000000' },
      TACF_16KHZ: { value: '%00000011' },
      TACF_65KHZ: { value: '%00000010' },
      TACF_262KHZ: { value: '%00000001' },
    },
  },

  rIF: {
    description:
      "Interrupt Flag (R/W)\nContains the currently 'ready' interrupts, set by hardware, cleared when interrupt is executed.\nGenerally only written to zero to clear pending interrupts before enabling interrupts.",
    value: '$FF0F',
    flags: 'rIE',
  },

  rLCDC: {
    description: 'LCD Control (R/W)',
    value: '$FF40',
    flags: {
      LCDCF_OFF: { value: '%00000000', description: 'LCD Control Operation' },
      LCDCF_ON: { value: '%10000000', description: 'LCD Control Operation' },
      LCDCF_WIN9800: {
        value: '%00000000',
        description: 'Window Tile Map Display Select',
      },
      LCDCF_WIN9C00: {
        value: '%01000000',
        description: 'Window Tile Map Display Select',
      },
      LCDCF_WINOFF: { value: '%00000000', description: 'Window Display' },
      LCDCF_WINON: { value: '%00100000', description: 'Window Display' },
      LCDCF_BG8800: {
        value: '%00000000',
        description: 'BG & Window Tile Data Select',
      },
      LCDCF_BG8000: {
        value: '%00010000',
        description: 'BG & Window Tile Data Select',
      },
      LCDCF_BG9800: {
        value: '%00000000',
        description: 'BG Tile Map Display Select',
      },
      LCDCF_BG9C00: {
        value: '%00001000',
        description: 'BG Tile Map Display Select',
      },
      LCDCF_OBJ8: { value: '%00000000', description: 'OBJ Construction' },
      LCDCF_OBJ16: { value: '%00000100', description: 'OBJ Construction' },
      LCDCF_OBJOFF: { value: '%00000000', description: 'OBJ Display' },
      LCDCF_OBJON: { value: '%00000010', description: 'OBJ Display' },
      LCDCF_BGOFF: { value: '%00000000', description: 'BG Display' },
      LCDCF_BGON: { value: '%00000001', description: 'BG Display' },
    },
  },

  rSTAT: {
    description: 'LCDC Status (R/W)',
    value: '$FF41',
    flags: {
      STATF_LYC: {
        value: '%01000000',
        description: 'LYC=LY Coincidence interrupt enabled (writable)',
      },
      STATF_MODE10: {
        value: '%00100000',
        description: 'Mode 10 OAM STAT interrupt enabled (writable)',
      },
      STATF_MODE01: {
        value: '%00010000',
        description: 'Mode 01 V-Blank STAT interrupt enabled (writable)',
      },
      STATF_MODE00: {
        value: '%00001000',
        description: 'Mode 00 H-Blank STAT interrupt enabled (writable)',
      },
      STATF_LYCF: { value: '%00000100', description: 'Coincidence Flag' },
      STATF_HB: { value: '%00000000', description: 'H-Blank' },
      STATF_VB: { value: '%00000001', description: 'V-Blank' },
      STATF_OAM: {
        value: '%00000010',
        description: 'OAM-RAM is used by system',
      },
      STATF_LCD: {
        value: '%00000011',
        description: 'Both OAM and VRAM used by system',
      },
      STATF_BUSY: {
        value: '%00000010',
        description: 'When set, VRAM access is unsafe',
      },
    },
  },

  rSCY: {
    description: 'Scroll Y (R/W)',
    value: '$FF42',
  },
  rSCX: {
    description: 'Scroll X (R/W)',
    value: '$FF43',
  },

  rLY: {
    description: 'LCDC Y-Coordinate (R)<br>Values range from 0->153. 144->153 is the VBlank period.',
    value: '$FF44',
  },

  rLYC: {
    description: 'LY Compare (R/W)<br>When LY==LYC, STATF_LYCF will be set in STAT',
    value: '$FF45',
  },

  rDMA: {
    description: 'DMA Transfer and Start Address (W)',
    value: '$FF46',
  },

  rBGP: {
    description:
      'BG Palette Data (W)<br>Bit 7-6 - Intensity for %11<br>Bit 5-4 - Intensity for %10<br>Bit 3-2 - Intensity for %01<br>Bit 1-0 - Intensity for %00',
    value: '$FF47',
  },

  rOBP0: {
    description:
      'Object Palette 0 Data (W)<br>Bit 7-6 - Intensity for %11<br>Bit 5-4 - Intensity for %10<br>Bit 3-2 - Intensity for %01<br>Bit 1-0 - Ignored, %00 is transparent',
    value: '$FF48',
  },
  rOBP1: {
    description:
      'Object Palette 1 Data (W)<br>Bit 7-6 - Intensity for %11<br>Bit 5-4 - Intensity for %10<br>Bit 3-2 - Intensity for %01<br>Bit 1-0 - Ignored, %00 is transparent',
    value: '$FF49',
  },

  rWY: {
    description: 'Window Y Position (R/W)<br>0 <= WY <= 143',
    value: '$FF4A',
  },
  rWX: {
    description: 'Window X Position (R/W)<br>7 <EQU WX <EQU 166',
    value: '$FF4B',
  },

  rKEY1: {
    description:
      'Select CPU Speed (R/W) GBC Only!<br>Bit 7 contains current speed: 1 is double speed.<br>Write bit 0 to 1 and execute a STOP instruction to switch speed.',
    value: '$FF4D',
  },

  rVBK: {
    description: 'Select Video RAM Bank (R/W) GBC Only!',
    value: '$FF4F',
  },

  rHDMA1: {
    description: 'Horizontal Blanking, General Purpose DMA (W) GBC Only!',
    value: '$FF51',
  },
  rHDMA2: {
    description: 'Horizontal Blanking, General Purpose DMA (W) GBC Only!',
    value: '$FF52',
  },
  rHDMA3: {
    description: 'Horizontal Blanking, General Purpose DMA (W) GBC Only!',
    value: '$FF53',
  },
  rHDMA4: {
    description: 'Horizontal Blanking, General Purpose DMA (W) GBC Only!',
    value: '$FF54',
  },
  rHDMA5: {
    description: 'Horizontal Blanking, General Purpose DMA (R/W) GBC Only!',
    value: '$FF55',
  },

  rRP: {
    description: 'Infrared Communications Port (R/W) GBC Only!',
    value: '$FF56',
  },

  rBCPS: {
    description: 'Background Color Palette Specification (R/W) GBC Only!',
    value: '$FF68',
  },
  rBCPD: {
    description: 'Background Color Palette Data (R/W) GBC Only!',
    value: '$FF69',
  },

  rOCPS: {
    description: 'Object Color Palette Specification (R/W) GBC Only!',
    value: '$FF6A',
  },

  rOCPD: {
    description: 'Object Color Palette Data (R/W) GBC Only!',
    value: '$FF6B',
  },

  rSVBK: {
    description: 'Select Main RAM Bank (R/W) GBC Only!',
    value: '$FF70',
  },

  rIE: {
    description: 'Interrupt Enable (R/W)',
    value: '$FFFF',
    flags: {
      IEF_HILO: {
        value: '%00010000',
        description: 'Transition from High to Low of Pin number P10-P13',
      },
      IEF_SERIAL: {
        value: '%00001000',
        description: 'Serial I/O transfer end',
      },
      IEF_TIMER: { value: '%00000100', description: 'Timer Overflow' },
      IEF_LCDC: { value: '%00000010', description: 'LCDC (see STAT)' },
      IEF_VBLANK: { value: '%00000001', description: 'V-Blank' },
    },
  },

  //AUDVOL/NR50 ($FF24)
  rNR50: {
    description:
      'Channel control / ON-OFF / Volume (R/W)<br>Bit 7   - Vin->SO2 ON/OFF (Vin??)<br>Bit 6-4 - SO2 output level (volume) (# 0-7)<br>Bit 3   - Vin->SO1 ON/OFF (Vin??)<br>Bit 2-0 - SO1 output level (volume) (# 0-7)',
    value: '$FF24',
    alias: 'rAUDVOL',
    /* flags: {
            "AUDVOL_VIN_LEFT": { value: "%10000000", description: "SO2"},
            "AUDVOL_VIN_RIGHT": { value: "%00001000", description: "SO1"},
        } */
  },

  //AUDTERM/NR51 ($FF25)
  rNR51: {
    description:
      'Selection of Sound output terminal (R/W)<br>Bit 7   - Output sound 4 to SO2 terminal<br>Bit 6   - Output sound 3 to SO2 terminal<br>Bit 5   - Output sound 2 to SO2 terminal<br>Bit 4   - Output sound 1 to SO2 terminal<br>Bit 3   - Output sound 4 to SO1 terminal<br>Bit 2   - Output sound 3 to SO1 terminal<br>Bit 1   - Output sound 2 to SO1 terminal<br>Bit 0   - Output sound 0 to SO1 terminal',
    value: '$FF25',
    alias: 'rAUDTERM',
    flags: {
      //SO2
      AUDTERM_4_LEFT: { description: '%10000000' },
      AUDTERM_3_LEFT: { description: '%01000000' },
      AUDTERM_2_LEFT: { description: '%00100000' },
      AUDTERM_1_LEFT: { description: '%00010000' },
      //SO1
      AUDTERM_4_RIGHT: { description: '%00001000' },
      AUDTERM_3_RIGHT: { description: '%00000100' },
      AUDTERM_2_RIGHT: { description: '%00000010' },
      AUDTERM_1_RIGHT: { description: '%00000001' },
    },
  },

  //AUDENA/NR52 ($FF26)
  rNR52: {
    description:
      'Sound on/off (R/W)<br>Bit 7   - All sound on/off (sets all audio regs to 0!)<br>Bit 3   - Sound 4 ON flag (read only)<br>Bit 2   - Sound 3 ON flag (read only)<br>Bit 1   - Sound 2 ON flag (read only)<br>Bit 0   - Sound 1 ON flag (read only)',
    value: '$FF26',
    alias: 'rAUDENA',
    flags: {
      AUDENA_ON: { description: '%10000000' },
      AUDENA_OFF: { description: '%00000000  ; sets all audio regs to 0!' },
    },
  },

  ///SoundChannel #1 registers

  //AUD1SWEEP/NR10 ($FF10)
  rNR10: {
    description:
      'Sweep register (R/W)<br>Bit 6-4 - Sweep Time<br>Bit 3   - Sweep Increase/Decrease<br>&nbsp; 0: Addition<br>&nbsp; 1: Subtraction<br>Bit 2-0 - Number of sweep shift (# 0-7)<br>Sweep Time: (n*7.8ms)',
    value: '$FF10',
    alias: 'rAUD1SWEEP',
    flags: {
      AUD1SWEEP_UP: { description: '%00000000' },
      AUD1SWEEP_DOWN: { description: '%00001000' },
    },
  },

  //AUD1LEN/NR11 ($FF11)
  rNR11: {
    description:
      'Sound length/Wave pattern duty (R/W)<br>Bit 7-6 - Wave Pattern Duty (00:12.5% 01:25% 10:50% 11:75%)<br>Bit 5-0 - Sound length data (# 0-63)',
    value: '$FF11',
    alias: 'rAUD1LEN',
    flags: {
      AUDLEN_DUTY_12_5: { value: '%00000000', description: '12.5%' },
      AUDLEN_DUTY_25: { value: '%01000000', description: '25%' },
      AUDLEN_DUTY_50: { value: '%10000000', description: '50%' },
      AUDLEN_DUTY_75: { value: '%11000000', description: '75%' },
    },
  },

  //AUD1ENV/NR12 ($FF12)
  rNR12: {
    description: `Envelope (R/W)
Bit 7-4 - Initial value of envelope
Bit 3   - Envelope UP/DOWN
        0: Decrease
        1: Range of increase
Bit 2-0 - Number of envelope sweep (# 0-7)`,
    value: '$FF12',
    alias: 'rAUD1ENV',
    flags: {
      AUDENV_UP: { value: '%00001000' },
      AUDENV_DOWN: { value: '%00000000' },
    },
  },

  //AUD1LOW/NR13 ($FF13)
  rNR13: {
    description: 'Frequency lo (W)',
    value: '$FF13',
    alias: 'rAUD1LOW',
  },

  //AUD1HIGH/NR14 ($FF14)
  //Frequency hi (W)
  //
  //Bit 7   - Initial (when set, sound restarts)
  //Bit 6   - Counter/consecutive selection
  //Bit 2-0 - Frequency's higher 3 bits
  //
  rNR14: {
    description: 'Frequency hi (W)',
    value: '$FF14',
    alias: 'rAUD1HIGH',
    flags: {
      AUDHIGH_RESTART: { description: '%10000000' },
      AUDHIGH_LENGTH_ON: { description: '%01000000' },
      AUDHIGH_LENGTH_OFF: { description: '%00000000' },
    },
  },

  ///SoundChannel #2 registers

  rNR21: {
    description: 'Sound Length; Wave Pattern Duty (R/W)',
    value: '$FF16',
    alias: 'rAUD2LEN',
    flags: 'rAUD1LEN',
  },
  rNR22: {
    description: 'Envelope (R/W)',
    value: '$FF17',
    alias: 'rAUD2ENV',
    flags: 'rAUD1ENV',
  },
  rNR23: {
    description: 'Frequency lo (W)',
    value: '$FF18',
    alias: 'rAUD2LOW',
  },
  rNR24: {
    description: 'Frequency hi (W)',
    value: '$FF19',
    alias: 'rAUD2HIGH',
    flags: 'rAUD1HIGH',
  },

  ///SoundChannel #3 registers
  rNR30: {
    description: 'Sound on/off (R/W)',
    value: '$FF1A',
    alias: 'rAUD3ENA',
    //Bit 7   - Sound ON/OFF (1EQUON,0EQUOFF)
  },
  rNR31: {
    description: 'Sound length (R/W)',
    value: '$FF1B',
    alias: 'rAUD3LEN',
    //Bit 7-0 - Sound length
  },
  rNR32: {
    description: 'Select output level',
    value: '$FF1C',
    alias: 'rAUD3LEVEL',
    //Bit 6-5 - Select output level
    //          00: 0/1 (mute)
    //          01: 1/1
    //          10: 1/2
    //          11: 1/4
  },
  rNR33: {
    description: 'Frequency lo (W)',
    value: '$FF1D',
    alias: 'rAUD3LOW',
  },
  rNR34: {
    description: 'Frequency hi (W)',
    value: '$FF1E',
    alias: 'rAUD3HIGH',
    flags: 'rAUD1HIGH',
  },

  rNR41: {
    description: 'Sound length (R/W)',
    value: '$FF20',
    alias: 'rAUD4LEN',
    //Bit 5-0 - Sound length data (# 0-63)
  },

  rNR42: {
    description: 'Envelope (R/W)',
    value: '$FF21',
    alias: 'rAUD4ENV',
    flags: 'rAUD1ENV',
  },
  rNR43: {
    description: 'Polynomial counter (R/W)',
    value: '$FF22',
    alias: 'rAUD4POLY',
    //Bit 7-4 - Selection of the shift clock frequency of the (scf)
    //          polynomial counter (0000-1101)
    //          freqEQUdrf*1/2^scf (not sure)
    //Bit 3 -   Selection of the polynomial counter's step
    //          0: 15 steps
    //          1: 7 steps
    //Bit 2-0 - Selection of the dividing ratio of frequencies (drf)
    //          000: f/4   001: f/8   010: f/16  011: f/24
    //          100: f/32  101: f/40  110: f/48  111: f/56  (fEQU4.194304 Mhz)
  },

  rNR44: {
    description: '',
    value: '$FF23',
    alias: 'rAUD4GO',
    //Bit 7 -   Inital
    //Bit 6 -   Counter/consecutive selection
  },

  rPCM12: {
    description: 'Sound channel 1&2 PCM amplitude (R) GBC Only!',
    value: '$FF76',
    //Bit 7-4 - Copy of sound channel 2's PCM amplitude
    //Bit 3-0 - Copy of sound channel 1's PCM amplitude
  },
  rPCM34: {
    description: 'Sound channel 3&4 PCM amplitude (R) GBC Only!',
    value: '$FF77',
    //Bit 7-4 - Copy of sound channel 4's PCM amplitude
    //Bit 3-0 - Copy of sound channel 3's PCM amplitude
  },

  //Cart related
  CART_COMPATIBLE_DMG: {
    description: 'Store at $0143 to indicate DMG cartridge. ($00)',
  },
  CART_COMPATIBLE_DMG_GBC: {
    description: 'Store at $0143 to indicate DMG and GBC compatible cartridge. ($80)',
  },
  CART_COMPATIBLE_GBC: {
    description: 'Store at $0143 to indicate GBC compatible cartridge. ($C0)',
  },

  CART_ROM: { description: 'Store at $0147 to cart type. ($00)' },
  CART_ROM_MBC1: { description: 'Store at $0147 to cart type. ($01)' },
  CART_ROM_MBC1_RAM: { description: 'Store at $0147 to cart type. ($02)' },
  CART_ROM_MBC1_RAM_BAT: { description: 'Store at $0147 to cart type. ($03)' },
  CART_ROM_MBC2: { description: 'Store at $0147 to cart type. ($05)' },
  CART_ROM_MBC2_BAT: { description: 'Store at $0147 to cart type. ($06)' },
  CART_ROM_RAM: { description: 'Store at $0147 to cart type. ($08)' },
  CART_ROM_RAM_BAT: { description: 'Store at $0147 to cart type. ($09)' },
  CART_ROM_MBC3_BAT_RTC: { description: 'Store at $0147 to cart type. ($0F)' },
  CART_ROM_MBC3_RAM_BAT_RTC: {
    description: 'Store at $0147 to cart type. ($10)',
  },
  CART_ROM_MBC3: { description: 'Store at $0147 to cart type. ($11)' },
  CART_ROM_MBC3_RAM: { description: 'Store at $0147 to cart type. ($12)' },
  CART_ROM_MBC3_RAM_BAT: { description: 'Store at $0147 to cart type. ($13)' },
  CART_ROM_MBC5: { description: 'Store at $0147 to cart type. ($19)' },
  CART_ROM_MBC5_BAT: { description: 'Store at $0147 to cart type. ($1A)' },
  CART_ROM_MBC5_RAM_BAT: { description: 'Store at $0147 to cart type. ($1B)' },
  CART_ROM_MBC5_RUMBLE: { description: 'Store at $0147 to cart type. ($1C)' },
  CART_ROM_MBC5_RAM_RUMBLE: {
    description: 'Store at $0147 to cart type. ($1D)',
  },
  CART_ROM_MBC5_RAM_BAT_RUMBLE: {
    description: 'Store at $0147 to cart type. ($1E)',
  },
  CART_ROM_MBC7_RAM_BAT_GYRO: {
    description: 'Store at $0147 to cart type. ($22)',
  },
  CART_ROM_POCKET_CAMERA: { description: 'Store at $0147 to cart type. ($FC)' },

  CART_ROM_256K: {
    description: 'Store at $0148 to indicate the number of ROM banks: 2 banks',
  },
  CART_ROM_512K: {
    description: 'Store at $0148 to indicate the number of ROM banks: 4 banks',
  },
  CART_ROM_1M: {
    description: 'Store at $0148 to indicate the number of ROM banks: 8 banks',
  },
  CART_ROM_2M: {
    description: 'Store at $0148 to indicate the number of ROM banks: 16 banks',
  },
  CART_ROM_4M: {
    description: 'Store at $0148 to indicate the number of ROM banks: 32 banks',
  },
  CART_ROM_8M: {
    description: 'Store at $0148 to indicate the number of ROM banks: 64 banks',
  },
  CART_ROM_16M: {
    description: 'Store at $0148 to indicate the number of ROM banks: 128 banks',
  },
  CART_ROM_32M: {
    description: 'Store at $0148 to indicate the number of ROM banks: 256 banks',
  },
  CART_ROM_64M: {
    description: 'Store at $0148 to indicate the number of ROM banks: 512 banks',
  },

  CART_RAM_NONE: {
    description: 'Store at $0149 to indicate the amount of SRAM: No SRAM',
  },
  CART_RAM_16K: {
    description: 'Store at $0149 to indicate the amount of SRAM: 2 KiloByte, 1 bank',
  },
  CART_RAM_64K: {
    description: 'Store at $0149 to indicate the amount of SRAM: 8 KiloByte, 1 bank',
  },
  CART_RAM_256K: {
    description: 'Store at $0149 to indicate the amount of SRAM: 32 KiloByte, 4 banks',
  },
  CART_RAM_1M: {
    description: 'Store at $0149 to indicate the amount of SRAM: 128 KiloByte, 16 banks',
  },

  CART_RAM_ENABLE: {
    description: 'Write this value to $0000 to enable SRAM. ($0A)',
  },
  CART_RAM_DISABLE: {
    description: 'Write this value to $0000 to disable SRAM. ($00)',
  },

  //Keypad related
  PADF_DOWN: { description: '$80' },
  PADF_UP: { description: '$40' },
  PADF_LEFT: { description: '$20' },
  PADF_RIGHT: { description: '$10' },
  PADF_START: { description: '$08' },
  PADF_SELECT: { description: '$04' },
  PADF_B: { description: '$02' },
  PADF_A: { description: '$01' },

  PADB_DOWN: { description: '$7' },
  PADB_UP: { description: '$6' },
  PADB_LEFT: { description: '$5' },
  PADB_RIGHT: { description: '$4' },
  PADB_START: { description: '$3' },
  PADB_SELECT: { description: '$2' },
  PADB_B: { description: '$1' },
  PADB_A: { description: '$0' },

  //Screen related
  SCRN_X: {
    description: 'Width of screen in pixels',
    value: '160',
  },
  SCRN_Y: {
    description: 'Height of screen in pixels',
    value: '144',
  },
  SCRN_X_B: {
    description: 'Width of screen in bytes',
    value: '20',
  },
  SCRN_Y_B: {
    description: 'Height of screen in bytes',
    value: '18',
  },

  SCRN_VX: {
    description: 'Virtual width of screen in pixels',
    value: '256',
  },
  SCRN_VY: {
    description: 'Virtual height of screen in pixels',
    value: '256',
  },
  SCRN_VX_B: {
    description: 'Virtual width of screen in bytes',
    value: '32',
  },
  SCRN_VY_B: {
    description: 'Virtual height of screen in bytes',
    value: '32',
  },
};

for (var key in gameboy_hardware_constants) {
  if (typeof gameboy_hardware_constants[key].flags == 'string')
    gameboy_hardware_constants[key].flags = gameboy_hardware_constants[gameboy_hardware_constants[key].flags].flags;
  if (gameboy_hardware_constants[key].flags) {
    for (var flag in gameboy_hardware_constants[key].flags)
      gameboy_hardware_constants[flag] = gameboy_hardware_constants[key].flags[flag];
  }
  if (gameboy_hardware_constants[key].alias) {
    gameboy_hardware_constants[gameboy_hardware_constants[key].alias] = Object.assign(
      {},
      gameboy_hardware_constants[key],
    );
    gameboy_hardware_constants[gameboy_hardware_constants[key].alias].alias = key;
  }
}

export { gameboy_hardware_constants };