popBeeperSamples drains up to len(out) samples from the ring buffer into out. Any unfilled slots continue from the last delivered sample and then deca

Stack operations

screenHash returns a digest of the rendered frame, so a test can detect that the display changed (e.g. after typing or running a program).

sectorLength returns the byte length of a sector with size code n (µPD765 "N" parameter). Real floppies cap sector sizes at 128 << 8 = 32 KB; attacker

selectROM sets the ROM page based on the current port values. +2A / +3 / Next models combine 7FFD bit 4 (low bit) with 1FFD bit 2 (high bit) for a ful

setBC returns a setup that primes BC so block-op repeat vs final paths can be selected. Points HL/DE at writable high RAM so the copy doesn't fault.

start: SDA high->low while SCL high.

toFAT83 coerces a host filename to a FAT 8.3 short name. Uppercase ASCII only; everything else becomes '_'. Length truncated to 8 base + 3 ext.

writePortInternal is the original WritePort body. It contains the early-return cascade for each port family. Kept as a separate function so the public

AddPostFetchHook is the post-fetch analogue of AddPreFetchHook.

AddRecent prepends path to RecentFiles. Existing entries are deduplicated and the list is capped at MaxRecentFiles.

Cartridge returns the cartridge currently in microdrive slot `which` (0-based), or nil if the slot is empty or out of range. Convenience accessor so c

CheckBreakpoint fires for the visual debugger's bp set. Matches the telnet evaluator: optional ROM-bank filter + optional guard condition. Returns tru

DownloadNextROMs fetches the distro zip from url using client (pass nil for http.DefaultClient), then: - installs machines/next/enNextZX.rom and enNx

ExecuteRZXFrame runs the CPU until it has executed exactly `instructions` opcode fetches relative to the count at entry, then fires an end-of-frame in

FormatLine produces a one-line description suitable for the list-watches / visual panel.

GetKeyStatus returns a human-readable status of special keys

GetMultiface returns the Multiface interface (if enabled)

GetROM returns the data for a specific ROM type

GetVariant returns the Multiface variant

HandleMemoryRead handles memory reads that might be intercepted by peripherals

HandleOpcodeRead handles opcode fetch that might trigger ROM paging

HasROM reports whether a valid IF1 ROM has been loaded. The IF1 can't usefully activate without one — without the shadow ROM, none of the BASIC extens

HookFunc returns a pre-fetch callback that, when registered via cpu.AddPreFetchHook, fires the esxDOS dispatcher exactly when PC reaches $0008 AND the

IsInterface1Enabled reports whether the Interface 1 is currently active.

Level returns the current 8-bit level for the given channel. Channels outside ChannelA..ChannelD return 0.

LineWidth returns the active framebuffer width in pixels for the current resolution (256, 320 or 640).

LoadROM reads an 8 KB Interface 1 ROM image from disk. The standard distribution is `if1-2.rom` (Edition 2 of the IF1 ROM), the same file FUSE expects

Lookup returns the entry at pc, lock-free. Safe to call from the CPU hot path.

New returns a fresh Palette with every entry at 0 (black).

New builds a SAM machine from the two 16 KB ROM halves. z80.New resets the CPU (PC=$0000, ROM0 paged in) and the SAM frame interrupt is armed.

NewBreakpointSet returns an empty shared breakpoint set.

NewJSONEmitter wraps w. The encoder is configured with no indentation (so each event is exactly one line). onError is invoked once on the first write

NewLayerPriority returns a fresh priority store with all-zeros (the SLU "Sprites over Layer 2 over ULA" reset mode).

NewMachine constructs a ZX80/ZX81 (model must be roms.ModelZX80 or roms.ModelZX81). romPath is the ROM search directory ("" = embedded only).

NewRegWatchSet returns an empty watch set.

OnWriteFn returns the currently-installed OnWrite callback for the given register, or nil if none. Used by callers that want to chain a new behaviour

PageIn maps the IF1 shadow ROM over the Spectrum ROM area. The mapping mirrors the same 8 KB chunk into both halves of the 0x0000-0x3FFF window, exact

---------------------------------------------------------------------- MGT / IMG (DISCiPLE / +D) -----------------------------------------------------

Path returns the absolute path to config.json. The parent directory is created if missing.

PushBeeperSamples enqueues a batch of mono beeper samples generated by the ULA at end of frame. The samples are consumed by the oto playback goroutine

Refresh re-pulls the set and redraws.

Refresh re-pulls the store and triggers a list redraw. Cheap enough to call from the debugger's periodic tick.

RunUntilText runs frames until ScreenText contains the given substring or maxFrames have elapsed. Returns the frame count at which the text appeared,

SetAY attaches an AY-3-8912 source whose output will be mixed into the beeper stream. Pass nil to detach.

SetBankTracer installs a per-switch callback fired whenever the ROM bank in slot 0 changes (via port 7FFD bit 4, port 1FFD bit 2, or NextReg \$8E) or

SetCard installs (or removes) the SD-card slot. The slot receives SPI traffic on ports 0xE7 (chip select) and 0xEB (data). Passing nil detaches any ex

SetChip installs an existing AY at the given index, replacing the freshly-constructed one. Useful when the engine is layered on top of a host that alr

SetEnabled sets the enabled state

SetNextAY installs the Spectrum Next's three-chip AY engine. When set, port 0xFFFD / 0xBFFD traffic dispatches to the currently-active chip per NextRe

SetNextCompositor installs the Spectrum Next render stack's scanline compositor. Once installed, Render overlays the composited output on top of the 2

SetPrioritySource installs the LayerPriority reader. Without one the compositor defaults to ModeSLU (Sprites over Layer 2 over ULA).

SetWriteProtect sets the write-protect flag.

SplitROM validates a raw SAM Coupé system-ROM image and splits it into ROM0 (the low 16 KB, paged at $0000 on reset) and ROM1 (the high 16 KB, paged a

StopRecording finalises any in-progress recording.

Wait runs frames continuously for the given wall-clock duration at the simulated 50Hz frame rate (i.e. d / 20ms frames). Used for tests that just need

bcd converts an integer 0..99 to its BCD representation.

Clip-window registers NR$18 (Layer2), $19 (sprite), $1A (ULA), $1B (tilemap) are NOT single bytes: each holds four sub-coordinates (x1,x2,y1,y2) cycle

cmdBPFirstEntry arms a single-fire breakpoint that halts the CPU on the FIRST M1 fetch whose PC lies inside [LO, HI]. Auto-cleared on fire — `continue

cmdBankPoke parses `bank-poke KIND BANK OFF BYTES...` where each BYTE is a single hex value (no 0x prefix needed but accepted).

crashConfigFromFlags merges the per-heuristic CLI flags with the --crash-detect default. Per-heuristic flags always win over the default value; --cras

createSnapshotFromEmulator creates a snapshot from the current emulator state

dataAt walks from start looking for a data address mark (FB or F8 with the A1 sync prefix or clock bit). Returns (dataStart, deleted, ok) — dataStart

drainOne reads one byte from the card (one SPI clock byte).

envelopeLevel returns the 4-bit (0..15) envelope output value. The AY-mode DAC and the legacy 16-entry mixing path use env_vol's top four bits (audio/

generatePulses converts a tape block into a sequence of pulse durations (in T-states). Standard Spectrum (TAP / TZX 0x10) encoding: - Pilot tone: 216

isMultifacePort checks if the port matches this Multiface variant's decode. MF128 also responds to MF1's port pattern for backwards compatibility.

loadSymbolMap reads `addr name` lines into symbolTable. Lines starting with `#` or `;` are comments; blanks are skipped. The address is hex with opti

--------------------------------------------------------------------------- Helper: create a 16K page filled with a single byte ----------------------

makeReader returns a readFunc that serves the given bytes starting at address 0; out-of-range reads return 0xFF.

These tests cover the ring-buffer semantics of timeTravelBuffer directly (no live emulator). Capture and restore are exercised in integration: a headl

nextRunFrames runs the Next exactly as the GUI run loop does (frame execution plus the per-frame peripheral tick). A loaded .nex program must be run t

parsePCTriggers reads "NAME@$XXXX" or "NAME@$XXXX-$YYYY" pairs from the comma-separated --snapshot-on-pc value.

readDataError finishes a failed READ DATA without entering execution phase. The CHRN result fields echo the requested values from cmdBuf.

remaining returns the number of bytes free in the track.

tapKey presses a SAM matrix key (row, bit), holds it for a few frames so the 50 Hz ROM keyboard scan registers it, then releases it with a gap.

tick advances the macro by one frame. It must be called once per executed frame, after the frame runs, so keys pressed here are seen by the next frame

Add inserts or replaces the breakpoint at pc (copy-on-write).

AnyMotorOn reports whether any drive is currently spinning. Used by the UI to flash a "drive active" indicator.

Backtrace walks `n` stack words starting at sp (toward higher addresses, matching the Z80's stack-grows-downward convention) and classifies each via t

BuildFAT16 walks dir and produces an in-memory FAT16 image containing every file and subdirectory under it. The returned []byte is exactly opts.SizeMB

Capacity is the number of 512-byte blocks. Used for the CSD response so the host knows the card size.

DataAt is the exported entry point for locating the data address mark following an IDAM. Returns the position of the first data byte.

DivMMCRom3Gate reports whether a rom3-variant divMMC automap entry point (NR$B9 bit CLEAR) is allowed to engage, per zxnext.vhd:3138: (sram_altrom_e