dumpScreen writes the current frame to a PNG if SAM_RENDER_OUT_DIR is set.

Covers the IF1-enabled microdrive paths in PeripheralManager; the disabled-IF1 nil-guard branches are covered separately.

envApplied returns the envelope-controlled L/R amplitude; the right channel is inverted when the envelope's L/R-mirror bit (bit 0) is set.

fetch reads the next byte at PC and increments R (opcode fetch only).

flush writes any buffered tape lines to the underlying writer.

flushTo renders rendered-frame lines [renderCursor, target) and advances the cursor. Each line is drawn with the border/CLUT/screen state current at t

formatLayerState renders the decoded video-layer configuration from the relevant NextRegs, read via rd. Pure function (reader injected) for unit testi

getFormatName returns a human-readable name for the snapshot format

installFakeDistroForLoad writes a 16K distro ROM so memory.New can succeed in tests that need a constructed harness. MUST be preceded by installtest.

Interrupt + NMI T-state counts, IM 0/1/2 vector handling, and NMI semantics (vector $0066, PC push, IFF/IM effects): IM1=13T, IM2=19T, NMI=11T. intCPU

makeTestMemory creates a Memory bound to a test ROM directory so PageMapWidget.Refresh has real values to read.

mode decode (multiface.vhd:105-118)

newReadTape builds a recorder writing to w. Recording arms at the startHit-th execution of startPC; with startPC==0 && startHit<=0 it arms immediately

Covers the remoteDebugger bank-command parsers — cmdBankPeek / cmdBankPoke / cmdDisasmBank / cmdListBanks. These take raw arg slices and return protoc

Covers emuBanks.Bank / BankPeek / BankPoke for the memory-only kinds (ram, rom, altrom). The divmmc-ram path requires an *emulator and is tested separ

This file proves the faithful path for loading .nex games that depend on the NextZXOS runtime: instead of bank-injecting (which overwrites the OS's ow

oneLine collapses a multi-line debugger response into a single line for slog readability. The full response is still complete; this just replaces \r\n

physicalDrive returns the physical drive index (0 = A, 1 = B) for a µPD765 unit-select value. The +3 only wires US0, so of the two US bits only bit 0

process high-pass-filters samples in place. The first sample after a reset lazily seeds the filter from the current level, so a steady power-on/reset

ramPage returns the read/write pointers for internal RAM page p (masked to 5 bits); absent pages (e.g. 16-31 on a 256K machine) resolve to scratch.

readByte returns the byte at position i, substituting random data if the byte is marked weak. Used by the FDC's data transfer path; speed matters more

regName returns the canonical register name for the 3-bit register encoding used in Z80 instruction tables: 0=B 1=C 2=D 3=E 4=H 5=L 6=(HL) 7=A.

WZ/MEMPTR for DDCB / FDCB indexed instructions. Per Sean Young's "Undocumented Z80 Documented" §3.4, every DDCB / FDCB instruction sets MEMPTR = IX+d

SLL / SLI undocumented opcode tests. SLL ("Shift Left Logical" — sometimes called SLI for "Shift Left and Insert") is the CB-prefix opcode set $30-$3

saaWrite drives the SAA1099 through the SAM port interface: address latch on port 0x01FF, data on port 0x00FF.

The SAM ASIC exposes the raster position through two read-only "light pen" registers on port 0xF8: LPEN (port & 0x1FF == 0x0F8, horizontal) and HPEN (

screenAddrForRowCol returns the offset within a 16K screen RAM page where pixel-row `row` (0..191), column `col` (0..31, units of 8 pixels) is stored.

sdaLine is the wired-AND bus level both parties observe.

selectedBank returns the divMMC RAM bank index (0..NumBanks-1) that should be visible at 0x2000-0x3FFF, based on the low bits of port 0xE3.

sendCommandNoCSToggle emits a 6-byte command frame without touching CS. Used to model the FPGA bootrom's init pattern, which asserts CS once and keeps

WZ/MEMPTR on repeating block instructions. Per Sean Young's "Undocumented Z80 Documented" §4.2: every repeating block instruction (LDIR / LDDR / CPIR

sharedBreakpoints returns the emulator's single shared breakpoint store, creating it on first use. Both the telnet debugger and the visual debugger ca

startNexloadMacro reboots into a clean NextZXOS and begins driving the .nexload command to load the .nex at sdPath (an absolute SD-card path) via the

stop: SDA low->high while SCL high.

stopInput closes the active input block. Idempotent. Called automatically by AddSnap and Stop.

stopRZXPlayback tears down an active playback session. Idempotent. Safe to call from any goroutine — the atomic.Pointer clear plus the ULA hook clear

syncAllMMU resyncs all 8 MMU slots from the classic page maps. Called once at the end of each setupNN configuration and from Reset(); not called from

tapeAudioMuted reports whether beeper audio should be muted because a fast-tape load is in progress. Crucially this is decoupled from the per-tick tur

tick computes every combinational signal from the CURRENT (pre-edge) state — just as the VHDL processes read the registers' current values — then appl

writeBlock emits a generic block: the 1-byte ID, the 4-byte inclusive-of-header length, then the payload. blockLen MUST equal 1 (ID) + 4 (length) + le

writeRecording appends a mono sample buffer to the active WAV file.

writeScreenshotPNG renders the current frame and writes it as a PNG to w. Works for every machine type: emu.ula.Render() returns the composited frameb

writeSector is a helper for SCAN tests: writes a known byte pattern into sector R=1 cyl=0 of drive 0.

AY returns the AY-3-8912 sound chip instance, or nil for models that do not have one (e.g. the 48K).

ActiveBank returns the currently-installed active bank index.

BankPeek copies n bytes starting at `off` in `kind` bank `bank`. Returns ErrZeroLength if n <= 0, ErrOffsetOutOfRange if [off, off+n) exits the bank.

BankPoke writes `data` into `kind` bank `bank` starting at `off`. Returns ErrOffsetOutOfRange if the write would exit the bank.

BeamPosition returns the current raster beam position derived from the CPU T-state counter: the scanline (0-based, 9-bit) and the horizontal position

Bitmap renders all accumulated rows as a greyscale image. Each pixel is either 0xFF (dark, burned by the stylus) or 0x00 (white). Returns an empty ima

Blocks returns a snapshot of the tape's block list. The slice is freshly allocated and safe for the caller to keep.

Capacity returns the maximum number of entries the ring can hold. Used by the debugger command to print "of N capacity" in the help / list output.

ComposeWideLayer2Row overlays the hi-res Layer 2 row onto dst, an RGBA row Layer2Width pixels wide already holding the lower layers.

DFFDValue returns the current $DFFD high RAM-bank extension value (bits 3:0). Exposed mainly for tests; production callers should derive bank mappings

Date returns the build timestamp formatted for humans as "YYYY-MM-DD HH:MM:SS UTC" (date, time, and time zone). It uses the ldflags-injected BuildDate

Dirty reports whether any guest write has landed in the image since load (or the last WriteBackTo). Drives the opt-in write-back policy: an untouched

Emit implements Emitter.

Empty reports whether the set has no active watches. Hot-path helper so the pre-fetch hook can skip the State allocation when there's nothing to do.

Empty reports whether any channel is enabled. When false, the CLI can skip every hook-install step and the program runs at full speed.

Finished reports whether the playback has run off the end of the file. After Frame returns ErrPlaybackFinished, this method returns true and all other

Frame-interrupt timing model, transcribed from the FPGA core so the whole class of INT-timing behaviour conforms in one place (timing.md §1a/§1c). See

Geometry reports the disk's cylinders, heads, sectors-per-track and sector size.

GetPortTracer returns the currently-installed PortTracer (or nil). Used by chained-tracer patterns where a new caller wants to run alongside any pre-e

GetRAMReadHook returns the currently-installed RAM-read hook, or nil. Allows chaining without clobbering a prior hook.

HandleMemoryWrite handles memory writes that might be intercepted by peripherals

HandlePortRead handles I/O port reads from peripherals

HasActiveTilemap reports whether the compositor has a tilemap layer wired AND enabled. ULA uses this to decide whether to run the border-area pass for

HasPalette reports whether the 512-byte palette block is present. The palette accompanies a loading screen unless the no-palette bit is set.

InsertInterface2Cartridge loads a 16KB .rom cartridge image and inserts it into the Interface 2 cartridge slot, then resets the CPU so the cartridge c

InsertMicrodrive places the supplied cartridge into the IF1's drive `which` (0-based). Used by tests and any caller that has already parsed a *microdr

Instruction returns the decoded instruction at index i. Indexes past MaxInstructions return a NOOP.

IntEnabled returns the interrupt-enable bit (o_int_en, ctc_chan.vhd:276).

Interface2CartridgeName returns the display name of the currently inserted cartridge, or an empty string if none is inserted.

IsMemSwapped reports whether ROM and RAM positions are swapped.

KempstonMouseMove accumulates host mouse deltas into the Kempston X / Y counters. No-op if the mouse isn't enabled.

LoadNEX parses a .NEX file and loads its banks into Spectrum Next memory, then prepares the CPU to run from the .NEX entry point (SP, PC, border set f

New returns a DAC with both devices disabled and the output centred (silent).

NewHistoryWide is like NewHistory but flags the buffer as "producers will populate BC/DE/HL/IX/IY on every Push". Viewers gate the wide columns on thi

NewMemoryWithRAM builds the SAM memory with internalKB (256 or 512) of internal RAM and externalMB (0..4) of external RAM, at the power-on register st

NewScreen returns an all-paper Screen that decodes characters via cg.

NextBootFilter returns a SkipFile predicate that excludes large distro files the early boot path doesn't need. Tunes the 1 GB FAT16 image down to a fe

OpenDir opens a directory for enumeration via Handle.NextEntry.

ParseTRD parses an in-memory TR-DOS TRD image. TR-DOS disks are always formatted as 2 sides × 80 cylinders × 16 sectors × 256 bytes (655360 bytes tota

PressSymbolShift sets or releases the SYMBOL SHIFT bit directly. Companion to PressCAPSShift for E-mode keyword entry.

Priority returns the 2-bit NR$44 priority for the entry.

ReadFile is a thin wrapper around Read that loads the file from disk first. Mirrors the Load(path) shape of pkg/snapshot.Snapshot so RZX file handling

ReadNR44 returns the NextReg $44 read-back. Per zxnext.vhd:6047 (nr_palette_dat(10 downto 9) & "00000" & nr_palette_dat(0)): bits 7:6 are the 2-bit pr