MCP Mgba vs MCP Bizhawk

mgba_read8

PURPOSE: Read an unsigned 8-bit byte from emulated memory at the given system bus address. USAGE: Use for single-byte status flags, counters, and 8-bit fields. For 16- or 32-bit values use mgba_read16/read32 (one call instead of multi-byte assembly); for spans of more than ~4 bytes use mgba_read_range (one round-trip instead of N frame-latency hops). Reads work the same way whether emulation is paused or running, so pause is optional but recommended when you need a coherent snapshot across multiple reads. BEHAVIOR: No side effects — pure read. Returns an error if the address is outside the platform's mapped regions or the bridge method is missing on this mGBA build. RETURNS: Single line 'ADDR_HEX: VAL_DEC (0xVAL_HEX)', e.g. '0x2000000: 99 (0x63)'. GBA address space: 0x02000000 EWRAM (256 KiB, general-purpose) 0x03000000 IWRAM (32 KiB, fast stack/variables) 0x04000000 IO registers 0x05000000 Palette RAM (1 KiB) 0x06000000 VRAM (96 KiB) 0x07000000 OAM (1 KiB) 0x08000000 ROM (up to 32 MiB, read-only) Game Boy / GBC address space (when running a GB/GBC ROM): 0x0000 ROM bank 0 (16 KiB, read-only on bus; writes here trigger MBC commands but mgba_write* bypasses the bus) 0x4000 ROM banked (switchable) 0x8000 VRAM (8 KiB) 0xA000 Cartridge SRAM (8 KiB) — disabled by default on MBC1/3/5 carts 0xC000 WRAM (8 KiB; CGB has banked extension to 0xD000) 0xFE00 OAM (160 B) 0xFF00 I/O registers 0xFF80 HRAM (127 B)

mgba_read16

PURPOSE: Read an unsigned 16-bit little-endian value from emulated memory at the given system bus address. USAGE: Use for 16-bit fields (most game-state values: HP, score, coordinates on 16-bit-flavoured layouts). For single bytes use mgba_read8; for 32-bit values use mgba_read32; for non-aligned spans, big-endian fields, or arbitrary structures use mgba_read_range and decode the bytes yourself (this tool always interprets bytes as little-endian, which matches both GBA and GB/GBC native endianness). BEHAVIOR: No side effects — pure read. Reads two consecutive bytes (low byte at `address`, high byte at `address+1`) and combines them as little-endian. Returns an error if the address is unmapped, the read straddles a region boundary, or the bridge method is missing on this build. RETURNS: Single line 'ADDR_HEX: VAL_DEC (0xVAL_HEX)'.

mgba_read32

PURPOSE: Read an unsigned 32-bit little-endian value from emulated memory at the given system bus address. USAGE: Use for 32-bit fields (timestamps, large counters, pointers on GBA, RGBA colours). For 8/16-bit reads use mgba_read8/read16; for big-endian or unaligned multi-word reads use mgba_read_range and decode yourself. BEHAVIOR: No side effects — pure read. mGBA's native emu.read32 is intermittently flaky when called via pcall on certain builds, so the bridge transparently routes 32-bit reads through readRange(addr, 4) and reassembles them little-endian — you get a stable answer either way. Returns an error only if the address is unmapped or the underlying readRange itself fails. RETURNS: Single line 'ADDR_HEX: VAL_DEC (0xVAL_HEX)'.

mgba_read_range

PURPOSE: Read a contiguous range of bytes from emulated memory and return them as a hex-formatted dump. USAGE: Use whenever you need more than ~4 bytes — one round-trip vs N frame-latency hops compared to looping mgba_read8. Maximum 4096 bytes per call (bridge serialization limit); for larger reads, batch in 4 KiB chunks. The classic two-snapshot RAM-hunt workflow uses this: snapshot before a known change, snapshot after, diff for matching deltas. Also useful for inspecting unknown structures and for 'capture, modify, restore' write_range workflows. This is the same primitive that mgba_read32 routes through internally. BEHAVIOR: No side effects — pure read. Reads `length` consecutive bytes starting at `address`. Returns an error if length > 4096, length < 1, the start address is unmapped, or the read crosses an unmapped region. RETURNS: Header line 'ADDR_HEX [N bytes]:' followed by space-separated 2-digit uppercase hex bytes.

mgba_write8

PURPOSE: Write a single unsigned byte (0-255) to emulated memory at the given system bus address. USAGE: Use for single-byte cheats, debug pokes, and game-state mutations (give a player N lives, unlock a flag, set a counter). For 16/32-bit values prefer mgba_write16/write32 (single call instead of byte-at-a-time); for spans use mgba_write_range. To seed cart save RAM realistically (with proper MBC bank/enable behavior on Game Boy, or to install a known-good progression state on GBA), prefer mgba_save_state / mgba_load_state with a pre-prepared state file rather than poking SRAM bytes here. BEHAVIOR: DESTRUCTIVE: overwrites whatever was at `address` with no undo (snapshot via mgba_save_state first if you need rollback). The write is debug-direct memory access — bypasses MBC bank switches, cartridge mapper side-effects, RAM-enable gates, and bus protections — so it cannot be used to emulate cartridge hardware. Writes to ROM region addresses succeed at the memory level but produce no MBC effect on GB/GBC. Returns an error if the address is unmapped, value < 0 or > 255, or the bridge method is missing. Works whether emulation is paused or running. RETURNS: Single line 'Wrote VAL_DEC (0xVAL_HEX) → ADDR_HEX'. NOTE: writes use mGBA's debug-direct memory access, which bypasses the cartridge bus model. On Game Boy with an MBC cartridge, this means writes to ROM region (0x0000-0x7FFF) won't trigger MBC bank-switch / RAM-enable commands, and writes to SRAM (0xA000-0xBFFF) hit the underlying buffer regardless of MBC enable state. To seed cartridge SRAM cleanly, use mgba_save_state / mgba_load_state with a pre-prepared state file.

mgba_write16

PURPOSE: Write an unsigned 16-bit little-endian value to emulated memory at the given system bus address. USAGE: Use for 16-bit cheats and pokes (HP, score, coordinates). For single bytes use mgba_write8; for 32-bit use mgba_write32; for big-endian fields, byteswap and use mgba_write_range; for cart save RAM seeding with proper MBC semantics, use mgba_save_state / mgba_load_state. BEHAVIOR: DESTRUCTIVE: overwrites two bytes (low byte at `address`, high byte at `address+1`) with no undo. Debug-direct memory write — no MBC/mapper/DMA mediation, see mgba_write8 notes for the cartridge-bus bypass details. Returns an error if the address is unmapped, address+2 crosses an unmapped boundary, value < 0 or > 65535, or the bridge method is missing. RETURNS: Single line 'Wrote VAL_DEC (0xVAL_HEX) → ADDR_HEX'. NOTE: writes use mGBA's debug-direct memory access, which bypasses the cartridge bus model. On Game Boy with an MBC cartridge, this means writes to ROM region (0x0000-0x7FFF) won't trigger MBC bank-switch / RAM-enable commands, and writes to SRAM (0xA000-0xBFFF) hit the underlying buffer regardless of MBC enable state. To seed cartridge SRAM cleanly, use mgba_save_state / mgba_load_state with a pre-prepared state file.

mgba_write32

PURPOSE: Write an unsigned 32-bit little-endian value to emulated memory at the given system bus address. USAGE: Use for 32-bit cheats and pokes (timestamps, large counters, pointers on GBA). For 8/16-bit values use mgba_write8/write16; for big-endian layouts byteswap and use mgba_write_range. BEHAVIOR: DESTRUCTIVE: overwrites four bytes starting at `address` with no undo (snapshot via mgba_save_state first if you need rollback). Debug-direct memory write — bypasses MBC/mapper/DMA, see mgba_write8 notes. Returns an error if the address is unmapped, address+4 crosses an unmapped boundary, value < 0, or the bridge method is missing. RETURNS: Single line 'Wrote VAL_DEC (0xVAL_HEX) → ADDR_HEX'. NOTE: writes use mGBA's debug-direct memory access, which bypasses the cartridge bus model. On Game Boy with an MBC cartridge, this means writes to ROM region (0x0000-0x7FFF) won't trigger MBC bank-switch / RAM-enable commands, and writes to SRAM (0xA000-0xBFFF) hit the underlying buffer regardless of MBC enable state. To seed cartridge SRAM cleanly, use mgba_save_state / mgba_load_state with a pre-prepared state file.

mgba_write_range

PURPOSE: Write a contiguous byte sequence to emulated memory starting at the given system bus address. USAGE: Use whenever you're seeding more than ~4 bytes — one round-trip vs N frame-latency hops compared to looping mgba_write8. Maximum 4096 bytes per call (bridge serialization limit); for larger writes, batch in 4 KiB chunks. Useful for installing cheat tables, patching code blocks, restoring a captured byte window after experiments, and writing big-endian multi-byte values (byteswap them yourself first). For cart save RAM seeding with proper MBC semantics on Game Boy, use mgba_save_state / mgba_load_state instead — those go through the cartridge bus model. BEHAVIOR: DESTRUCTIVE: overwrites N bytes starting at `address` with no undo. Debug-direct memory write — bypasses MBC/mapper/DMA, see mgba_write8 notes for the cartridge-bus bypass details. Bytes are written sequentially address, address+1, ..., address+N-1. Returns an error if the address is unmapped, address+N crosses an unmapped boundary, the array contains a value outside 0-255, the array length is < 1 or > 4096, or the bridge method is missing. RETURNS: Single line 'Wrote N bytes → ADDR_HEX'. NOTE: writes use mGBA's debug-direct memory access, which bypasses the cartridge bus model. On Game Boy with an MBC cartridge, this means writes to ROM region (0x0000-0x7FFF) won't trigger MBC bank-switch / RAM-enable commands, and writes to SRAM (0xA000-0xBFFF) hit the underlying buffer regardless of MBC enable state. To seed cartridge SRAM cleanly, use mgba_save_state / mgba_load_state with a pre-prepared state file.

mgba_press_buttons

PURPOSE: Append a button-press to mGBA's input FIFO — hold the given buttons for `frames` frames, then release for `release_frames` frames before the next queued press starts. USAGE: Use to drive games with input. Each call APPENDS to the queue rather than overwriting, so consecutive calls produce distinct edge events that ROMs see as separate presses (rather than one continuous hold). To press the same button twice in a row reliably, send two presses — `release_frames` between them gives the ROM time to detect a key-up, which most input handlers require to register the second press. To advance emulation manually (without queueing inputs), use mgba_advance_frames. To inspect input-state side effects, pause first with mgba_pause and read RAM between presses. BEHAVIOR: Modifies the bridge's input queue; the press fires asynchronously on mGBA's frame callback. The call returns immediately with the new queue size — it does NOT block until the press completes. Returns an error if `buttons` contains a name not in the valid-key set, or if the bridge's input handling isn't installed on this build. RETURNS: Single line 'Queued press: KEYS (hold Nf, release Mf). Queue size: K'. Valid button names: A, B, Select, Start, Right, Left, Up, Down, R, L.

mgba_advance_frames

PURPOSE: Step emulation by exactly N frames synchronously and return the new frame count. USAGE: Use for frame-precise input automation (combine with mgba_press_buttons to time inputs against in-game animation), letting the system initialize after a hard reset (RAM is mostly zero in the first ~30 frames after mgba_reset), or settling state between memory reads. For long jumps (thousands of frames) prefer mgba_save_state / mgba_load_state of a pre-prepared state — advance_frames scales linearly. To resume real-time playback indefinitely instead of stepping, use mgba_unpause. Works whether emulation is currently paused or running and does NOT change the pause state. BEHAVIOR: Advances mGBA's frame clock by N frames inside the bridge's frame callback. Each step costs roughly one real frame (~16ms at 60Hz GBA / ~16.7ms at 60Hz GB) plus one bridge round-trip — so advancing 600 frames takes ~10 seconds wall-clock. This method is build-dependent on mGBA; check `capabilities.frameAdvance` in mgba_get_info first. Returns an error if the capability is missing on this build. RETURNS: Single line 'Advanced N frame(s). Current frame: NEW_COUNT'.