NewMemory builds the SAM memory with 512 KB internal RAM and no external RAM (the default config) from the two 16 KB ROM halves.

NewMicrodriveBus creates a fresh bus with no cartridges inserted and all drives idle. Each slot starts with a freshly-allocated blank Cartridge so the

NextByte returns the next IN-port byte for the current frame. The ULA's RZX playback hook calls this for every CPU IN instruction. Returns ErrPlayback

RGB returns the (red, green, blue) channels for the entry at index, each expanded from its 3-bit packed form to a full 8-bit channel value via the sta

Reset clears all registers and internal state.

Add with carry

envLevel returns the current 0-15 envelope level for generator g.

fakeSystem produces an AudioSystem instance that's safe to use without an oto context — we exercise the queue logic only, not the playback path.

Inc/Dec operations with proper flag handling

Subtract with carry (borrow)

Disassemble disassembles count instructions starting from addr.

GetAltROM exposes one of the two alt-ROM 16K buffers as a slice for the debugger's bank-inspect path. Bank 0/1 only; out-of-range returns nil.

GetDisciple returns the Disciple interface (if enabled)

HandlePortRead is the peripheral-manager-compatible read handler. Decodes the port address against the three Kempston patterns and returns the corresp

HandlePortRead handles reads from Multiface I/O ports. On real hardware, IN to the Multiface port controls page-in/page-out based on A7: A7=1 pages in

HandleWrite is the memory.PeripheralWrite hook. Writes to the 0x2000-0x3FFF window land in the bank selected by port 0xE3 EXCEPT when MAPRAM is set an

LoadROM loads a single ROM file. It tries the embedded ROMs first, then falls back to the filesystem path.

New returns a dispatcher with the boot-path minimum handler set (M_GETHANDLE, M_DRVAPI) pre-registered. File API handlers (F_OPEN, F_READ, etc.) are N

--- parser --- ParseCondition tokenizes + parses an expression. Returns an error positioning the failure within the input.

ParseDSK parses a DSK image from a byte slice. Both the original CPCEMU "MV - CPCEMU Disk-File" format and the EXTENDED CPC DSK variant are supported.

SetSpeedSelect installs the NextReg 0x07 speed selector. Only the low 2 bits are honoured; other bits are ignored. A no-op once the speed has been loc

StepInstructionWithIRQ executes one Z80 instruction at the M1 sample point — mirrors the per-iteration body of ExecuteFrame so that debugger-driven si

TapKey presses a key, runs holdFrames frames, releases it, then runs gapFrames more frames. The default values (3 hold + 2 gap) give the Spectrum's ke

WriteData feeds the next byte of a write transfer (Beta port $7F write), or just latches the data register when no write is in flight (e.g. before a S

decompressZ80 decompresses Z80 RLE compressed data

newTestULA constructs a minimal ULA for the RZX hook tests, reusing the test-ROM helpers from ula_test.go so we don't need a separate memory construct

redirectConfig is the local in-package helper. Cross-package callers should use install/installtest.RedirectConfig. We can't just import installtest h

statusByte computes the active-low interrupt bits (1 = inactive) from the current frame-relative T-state: the frame INT is pending for samIntActiveCyc

Checksum verifies the three checksum fields of block N against the stored data using the same Z80-style ADC loop as the IF1 ROM (microdrive.c:185-250)

Disabled reports whether AY output is suppressed (NextReg 0x06 bits 1-0 == 11, "hold all AY in reset").

Eval evaluates the parsed condition against the current state. Errors are programmer bugs (e.g. unknown register name caught at parse time would mean

FindSector locates a sector by R on the track by walking the byte stream for matching IDAMs. Returns nil if not present. Used by tests for verificatio

IsMultifaceEnabled returns whether Multiface is enabled

LoadROMBytes installs an 8 KB ROM image from a byte slice. Used by the embedded-ROM fallback path in pkg/roms.

New returns a Bank with all channels at level 0 (silent).

New returns an RTC backed by the host system clock.

ReadStatus returns the Main Status Register byte. The CPU reads this from port 0x2FFD on the +3.

RemovePreFetchHook deregisters a pre-fetch hook by name. Safe to call for a name that was never registered.

Root returns the panel's top-level object.

Save writes config.json atomically (write-temp + rename) so a crash mid-write doesn't truncate the existing config.

Set updates the stored byte.

Start positions the cursor at the `which`-th input recording block (0-indexed, ignoring non-IRB blocks) and returns the snapshot block that immediatel

Status returns the NextReg 0xA9 status byte: TX-ready always set (we accept any byte), RX-ready set when rxBuf has pending bytes.

StoreFrame closes the in-progress frame, recording the supplied instruction count alongside the IN bytes captured since the previous StoreFrame. The b

WirePeripheralMasks installs OnWrite handlers for NR$81, $85, $89, $8A that apply the reserved-bit masks the FPGA enforces. Without these, the dispatc

decodePort returns the port class for an I/O address.

newBlankInert builds a machine and asserts the inert-peripherals invariant indirectly by never wiring a Spectrum peripherals manager — the machine own

newNextEmulator constructs the production Spectrum Next emulator from scratch (cold start). For runtime model switches use the classic newEmulator(mod

onM1Fetch implements the CPU-generated display: an M1 fetch from the upper 32K (A15 = 1) with bit 6 clear is turned into a NOP while its byte is drawn

record appends a row, evicting the oldest when full.

======================================================================== Symbol map tests. ===========================================================

writeByte sends 8 bits MSB-first and samples the slave's ACK on the 9th clock. Returns true when the slave ACKed (SDA pulled low).

Bank returns a slice aliasing the physical bytes of bank number `bank` in `kind`. Writes to the returned slice MUST be visible to the running emulator

Get returns the raw byte.

GetTapePlayer returns the currently loaded tape player (or nil).

Memory returns the underlying memory.Memory.

New returns an empty UART. Initial state: TX FIFO has space, RX FIFO is empty, AT+GMR returns DefaultVersion.

NewPlayback wraps a parsed File for playback. Start must be called before any other method does useful work.

NewULA constructs a fresh IF1 ULA wrapping the supplied microdrive bus. If bus is nil a fresh one is allocated.

PatternByte returns the byte at the given pattern-RAM offset. Useful for tests; out-of-range returns 0.

ReadSector returns a copy of the 256-byte sector at (cylinder, side, sector).

RenderScanline renders one raster line of the LoRes/Radastan layer into dst (one byte = one 8-bit palette index per output pixel). vc is the raster Y

RenderScanline writes one row (LineWidth bytes) of palette-indexed pixels from the active framebuffer to dst, applying the FPGA's scroll + wrap + per-

SDCardRoot returns the host directory whose contents are exposed to the emulator as a virtual FAT16 SD card. Resolution order: 1. $ZX_GO_NEXT_SD_DIR

Selected returns the active chip index (0..2).

Paging-register writes (called by the I/O port dispatch). LMPR, HMPR, LEPR and HEPR change the CPU map; VMPR only selects the displayed page.

SetRAMWriteHook installs a debug callback fired on every successful RAM write that lands via the Memory.Write path. bank is the 16K SRAM index, addr i

SetTapePlayer sets the tape player for tape loading. The tape clock is re-synced to the current CPU T-state so playback starts "now" rather than jumpi

SpeedSelect returns the currently-installed NextReg 0x07 speed selector (0..3). Useful for snapshot save and for the dispatcher to read back what was

Tick is called once per simulated frame. If the frame index is a multiple of `every`, a snapshot is emitted to stderr (via slog) and optionally a scre

ULA returns the underlying ULA. Most tests should use the ScreenImage / ScreenText helpers instead of touching this directly.

WriteFile serialises the cartridge to disk at the given path.

newNextMem builds a ModelNext memory.Memory using the sandboxed install dir so the test never touches the user's real config. Mirrors the helper patte

popC pops a 16-bit value through contended read cycles (lo at SP, hi at SP+1).

runOneFrameHeadless advances the CPU by one ULA frame. Normally that's a single ExecuteFrame call. ZX_GO_STEP_FRAME=1 instead drives the CPU through t

transferCmd builds a complete zxnDMA / Z80-DMA command stream for a memory->memory transfer: RESET, WR0 (direction + src + length), WR1 (port A mode),

Count returns the live down-counter (o_cpu_d, ctc_chan.vhd:168).

DataAt reads the raw byte at the given absolute offset within the cartridge (0 .. Length()*BlockLen - 1). Used by the IF1 controller when streaming by