| Machine ID Register | $00 | Yes | No | Identifies TBBlue board type. Should always be 10 on Next. |
| Core Version Register | $01 | Yes | No | Identifies core (FPGA image) version. |
| Next Reset Register | $02 | Yes | Yes | Identifies type of last reset. Can be written to force reset. |
| Machine Type Register | $03 | Yes | Yes | Identifies timing and machine type. |
| Config Mapping Register | $04 | No | Yes | In config mode, allows RAM to be mapped to ROM area. |
| Peripheral 1 Register | $05 | Yes | Yes | Sets joystick mode, video frequency and Scandoubler. |
| Peripheral 2 Register | $06 | Yes | Yes | Enables CPU Speed key, DivMMC, Multiface, Mouse and AY audio. |
| CPU Speed Register | $07 | Yes | Yes | Sets CPU Speed, reads actual speed. |
| Peripheral 3 Register | $08 | Yes | Yes | ABC/ACB Stereo, Internal Speaker, SpecDrum, Timex Video Modes, Turbo Sound Next, RAM contention and [un]lock 128k paging. |
| Peripheral 4 Register | $09 | Yes | Yes | Sets scanlines, AY mono output, Sprite-id lockstep, reset DivMMC mapram and disable HDMI audio. |
| Peripheral 5 Register | $0A | Yes | Yes | Mouse buttons and DPI config |
| Core Version Register (sub minor) | $0E | Yes | No | Identifies core (FPGA image) version (sub minor number). |
| Anti-brick Register | $10 | Yes | Yes | Used within the Anti-brick system. |
| Video Timing Register | $11 | Yes | Yes | Sets video output timing variant. |
| Layer 2 RAM Page Register | $12 | Yes | Yes | Sets the bank number where Layer 2 video memory begins. |
| Layer 2 RAM Shadow Page Register | $13 | Yes | Yes | Sets the bank number where the Layer 2 shadow screen begins. |
| Global Transparency Register | $14 | Yes | Yes | Sets the "transparent" colour for Layer 2, ULA and LoRes pixel data. |
| Sprite and Layers System Register | $15 | Yes | Yes | Enables/disables Sprites and Lores Layer, and chooses priority of sprites and Layer 2. |
| Layer 2 X Offset Register | $16 | Yes | Yes | Sets the pixel offset used for drawing Layer 2 graphics on the screen. |
| Layer 2 Y Offset Register | $17 | Yes | Yes | Sets the Y offset used when drawing Layer 2 graphics on the screen. |
| Clip Window Layer 2 Register | $18 | Yes | Yes | Sets and reads clip-window for Layer 2. |
| Clip Window Sprites Register | $19 | Yes | Yes | Sets and reads clip-window for Sprites |
| Clip Window ULA/LoRes Register | $1A | Yes | Yes | Sets and reads clip-window for ULA/LoRes layer. |
| Clip Window Tilemap Register | $1B | Yes | Yes | Sets and reads clip-window for Tilemap. |
| Clip Window Control Register | $1C | Yes | Yes | Controls (resets) the clip-window registers indices. |
| Active Video Line MSB Register | $1E | Yes | No | Holds the MSB (only, as bit 0) of the raster line currently being drawn. |
| Active Video Line LSB Register | $1F | Yes | No | Holds the eight LSBs of the raster line currently being drawn. |
| Video Line Interrupt Control Register | $22 | Yes | Yes | Controls the timing of raster interrupts and the ULA frame interrupt. |
| Video Line Interrupt Value Register | $23 | Yes | Yes | Holds the eight LSBs of the line on which a raster interrupt should occur. |
| ULA X Offset Register | $26 | Yes | Yes | Pixel X offset (0..255) to use when drawing ULA Layer. |
| ULA Y Offset Register | $27 | Yes | Yes | Pixel Y offset (0..191) to use when drawing ULA Layer. |
| Keymap High Address Register | $28 | Yes | Yes | PS/2 Keymap address MSB, read (pending) first byte of palette colour |
| Keymap Low Address Register | $29 | No | Yes | PS/2 Keymap address LSB. |
| Keymap High Data Register | $2A | No | Yes | High data to PS/2 Keymap (MSB of data in bit 0) |
| Keymap Low Data Register | $2B | No | Yes | Low eight LSBs of PS/2 Keymap data. |
| DAC B (left) mirror Register | $2C | Yes | Yes | DAC B mirror, read current I2S left MSB |
| DAC A+D (mono) mirror Register | $2D | Yes | Yes | SpecDrum port 0xDF / DAC A+D mirror, read current I2S LSB |
| DAC C (right) mirror Register | $2E | Yes | Yes | DAC C mirror, read current I2S right MSB |
| Tilemap Offset X MSB Register | $2F | Yes | Yes | Sets the pixel offset (two high bits) used for drawing Tilemap graphics on the screen. |
| Tilemap Offset X LSB Register | $30 | Yes | Yes | Sets the pixel offset (eight low bits) used for drawing Tilemap graphics on the screen. |
| Tilemap Offset Y Register | $31 | Yes | Yes | Sets the pixel offset used for drawing Tilemap graphics on the screen. |
| LoRes X Offset Register | $32 | Yes | Yes | Pixel X offset (0..255) to use when drawing LoRes Layer. |
| LoRes Y Offset Register | $33 | Yes | Yes | Pixel Y offset (0..191) to use when drawing LoRes Layer. |
| Sprite port-mirror Index Register | $34 | Yes | Yes | Selects sprite index 0..127 to be affected by writes to other Sprite ports (and mirrors). |
| Sprite port-mirror Attribute 0 Register | $35 | No | Yes | Nextreg port-mirror to write directly into "byte 1" of Sprite Attribute Upload ($xx57 / 87). |
| Sprite port-mirror Attribute 1 Register | $36 | No | Yes | Nextreg port-mirror to write directly into "byte 2" of Sprite Attribute Upload ($xx57 / 87). |
| Sprite port-mirror Attribute 2 Register | $37 | No | Yes | Nextreg port-mirror to write directly into "byte 3" of Sprite Attribute Upload ($xx57 / 87). |
| Sprite port-mirror Attribute 3 Register | $38 | No | Yes | Nextreg port-mirror to write directly into "byte 4" of Sprite Attribute Upload ($xx57 / 87). |
| Sprite port-mirror Attribute 4 Register | $39 | No | Yes | Nextreg port-mirror to write directly into "byte 5" of Sprite Attribute Upload ($xx57 / 87). |
| Palette Index Register | $40 | Yes | Yes | Chooses an palette element (index) to manipulate with |
