fillPixelsTo writes the current stylus state into all pixels from p.pixel+1 through min(x, LineWidth-1), advances the fill cursor p.pixel, and flushes

findRepoRoot walks up from the current working directory looking for the nearest go.mod. Returns the absolute path of the containing directory and ok=

findSector searches the given track for an IDAM with the requested record ID, starting from startPos and walking at most one full revolution. It handl

finishTypeI sets the Type-I completion status (not busy, head loaded, Track-0 bit reflecting the head position) and raises INTRQ.

fireRAMReadHook invokes the RAM-read hook if installed. bank is the caller's reporting namespace: the 16K bank for pool reads, or the RAMPAGE page num

firstM1Divergence walks two aligned trace-row slices (oldest-first, e.g. from two emulators stepped in lockstep) and returns the first position where

formatHexDump renders data as a classic hexdump: one row per 16 bytes, each row = "$ADDR hh hh … hh |ascii|". Non-printable bytes show as '.' in the

formatPaletteDump renders the first `count` entries of a palette as a 9-bit-hex grid (16 per row, each row labelled with its starting index) followed

formatProvPhys renders one physical-pool last-writer record.

formatSpriteList renders the sprite bank: a header (enable + selected slot) then one line per VISIBLE sprite. get(i) returns the attribute for slot i;

fpgaPixel ports the Layer 2 pixel path (video/layer2.vhd:202-203): selects the 4bpp nibble in hi-res (res 10) — high nibble when sc1=false, low when t

Register access helpers for CB instructions

hexDump renders bytes as a 16-column address-prefixed hexdump. Format mirrors `xxd` so the output is easy to eyeball.

idAtCRC is the same as idAt but also returns whether the on-track CRC matches the computed CRC over the ID field. The walker is split into two entry p

installTraceHooks wires the trace emitter into every subsystem enabled by f.traceChannels. Returns the emitter so the caller can flush at shutdown, pl

isCallLike reports whether the given opcode pushes a return address — the operation a `step-over` should skip past. Covers: CALL nn :

isZX8x reports whether a model is a Sinclair ZX80 or ZX81.

l2Transparent reports whether a Layer 2 pixel at palette index idx is transparent. Real hardware compares the PALETTE-MAPPED 8-bit colour (the 8 MSB o

loadFPGATimingGolden parses testdata/ula_timing_golden.txt (captured from the real FPGA video timing generator video/zxula_timing.vhd under GHDL). Ret

loadInstalledDivMMCROM reads the divMMC ROM from the install path (same lookup the Spectrum Next emulator wiring uses). Returns nil if the file isn't

loadRealIF1ROM returns the embedded if1-2.rom bytes from pkg/roms. Used by the real-ROM integration tests below to validate the page-in/page-out trigg

loadSZXSpecRegs loads Spectrum-specific registers from SZX block

makeTestSnapshot builds a populated snapshot.Snapshot for the bridge round-trip tests. Every CPU register and memory bank carries a distinguishable pa

markRAMWritten records a guest write to pool byte (bank16k, off). Caller gates on m.TrackUninit.

newFloatingBusULA returns a 48K ULA with screen RAM pre-populated with a known pattern so floating-bus reads can be checked against expected values.

newSpecTestCPU creates a minimal CPU just for the line-int tests. We only need the FrameIntDisabled + LineIntOffsetTstates fields.

Port $FE write/read behaviour — beeper (bit 4), MIC (bit 3), border (bits 2:0) on write; EAR (bit 6) + reserved bits (5,7 read as 1) on read. Plus the

nexloadFromMenu drives the real NextZXOS NEXLOAD on sdPath. It expects the machine at the main menu with the cursor on "Browser" (as left by bootNextT

nextStep runs one CPU instruction through the IRQ-aware single-step path. The NextZXOS cold boot is driven by the per-instruction divMMC/esxDOS hooks

nullTerminated copies a fixed-width byte slice into a Go string, stopping at the first NUL. Used for the creator program name and the snapshot format

ordered returns the buffered rows oldest-first.

pageOut clears the automap-held latch and any not-yet-effective delayed_on page-in. A page-out (automap disable, $1FFx off-area, RETN) clears automap_

parseAddr accepts $XXXX, 0xXXXX, or decimal address strings. Returns the 16-bit value; errors on overflow or syntax.

parseCrashRegions decodes "NAME@LO-HI,NAME@LO-HI". Hex defaults for the address part — `$` and `0x` prefixes also accepted. Unparseable entries land i

parseDumpMemSpec parses the --dump-mem argument: `[bankN:|romN:]ADDR:LEN[,...]`, both ADDR and LEN hex (optional `$` / `0x` prefix). The optional `ban

parseFirstEntryRange accepts "$LO-$HI" or "$LO".

parseOffsetRange accepts "LO-HI" (both hex) or single-value "X" (which sets LO=HI=X).

parsePCRange decodes the START-END syntax accepted by --trace-pc-range. Both endpoints accept hex with $ or 0x prefix, or decimal. The end is inclusiv

parsePoolWriteSpec decodes "BANK:LO-HI[,BANK:LO-HI…]" (bank decimal, offsets hex with optional $/0x). HI optional (defaults to LO).

parseRAMWriteTraceSpec parses ZX_GO_RAM_WRITE_TRACE. Formats: "BB:LLLL-HHHH" (hex bank + offset range within the 16K bank) or "*:LLLL-HHHH" (all banks

poolScan searches every bank of the given kind for the byte pattern, returning up to max hits. Banks are probed until the accessor reports out-of-rang

preambleSlot returns the index into d.pream for the current head position. Slots 0..MaxBlocks-1 cover block headers; slots MaxBlocks..2*MaxBlocks-1 co

prefillSilence seeds the ring buffer with queuePrefill silent samples so the consumer's first few pulls are satisfied without draining the queue. See

pruneAutosaves implements FUSE's tiered autosave decay policy (rzx.c:557). Each automatic snapshot has a "frames before now" distance; if that distanc

queue appends bytes to the response queue.

quickLoadState restores the machine from the quick-save slot.

quickSavePath returns the quick-save slot file (an SZX snapshot) under the platform config dir, or "" if that dir can't be located.

quickSaveState writes the running machine to the quick-save slot.

quickSaveSupported reports whether the current machine supports SZX quick-save/load: the classic Spectrums (48K…+3) and Pentagon. The ZX80/ZX81 have n

quote and itoa are tiny helpers to avoid pulling fmt into a hot path that runs on every RunUntilText timeout. Worth nothing efficiency-wise, but consi

readPath reads a null- or 0xFF-terminated ASCII path string from the emulated memory bus starting at addr. The esxDOS convention accepts either termin

recomputeOutputs evaluates the three combinational outputs from the current register state and the live inputs (multiface.vhd:186,190-191,195).

refreshNext populates the 8-cell view for Next mode. Reads the 8K MMU shadow plus the divMMC overlay state; reports the 8K-bank index in each slot and

resolve converts an esxDOS path to a host filesystem path, rejecting any traversal that would escape root.

rowText returns the formatted line for row id, or empty if id is out of range. Reads from the snapshot refreshKeys() cached rather than re-querying th

runBPAction executes the semicolon-separated command list attached to a breakpoint via `bp ADDR ... do "..."`. Each command is parsed and dispatched t

ED-prefix IM mirror encodings. Per Sean Young's "Undocumented Z80 Documented" §A.1: IM 0: ED $46, $4E, $66, $6E IM 1: ED $56, $76 IM 2: ED $5E, $7E

IN r,(C) behavioural coverage. Per Sean Young's "Undocumented Z80 Documented" §3.6 and the Z80 ED-prefix decoder: ED $40 .. $78 cover IN B/C/D/E/H/L/

ED-prefix NEG mirror encodings. Per Sean Young's "Undocumented Z80 Documented" §A.1, ED $44, $4C, $54, $5C, $64, $6C, $74, $7C are all NEG mirror enc

saveNexShot writes a PNG when NEX_RENDER_OUT_DIR is set, for eyeballing.

saveSNA saves a snapshot in .SNA format

saveSZXRamPage saves a RAM page as SZX block

setupModel configures memory layout and loads ROMs for the specified model

The Layer 2 golden vectors are captured from the actual Spectrum Next FPGA Layer 2 renderer (video/layer2.vhd simulated under GHDL — see _tools/layer2

stepHead moves the physical R/W head one track in the given direction, clamping at track 0, and updates the Track Register only when the command's upd

These tests pin two behaviours where the Spectrum Next Z80N (T80N FPGA core) deviates from documented NMOS, discovered by the core-golden differential

synthDistroZip builds an in-memory zip shaped like the official sn-complete distro: a leading root folder, machines/next/*.rom, and a couple of SD-tre

tickEnvelope advances the envelope by one envelope clock, a faithful port of the FPGA env shape process (audio/ym2149.vhd:369-465). It mirrors the har

tileDefByte reproduces the tile-pixel formula the testbench writes into the tile definitions: pixel(x,y) nibble = 1 + ((x + 4*y) mod 15) (always opaqu

trdosTestROM returns a 16K blob with a recognisable per-byte pattern so a read can be attributed to the TR-DOS ROM rather than the system ROM.

usBits encodes a 0..3 drive index into the US0/US1 bits used by ST0/ST3.

wd1772StepRateMs returns the head stepping-motor rate in milliseconds for the Type I rate field r1r0, per the WD1772 datasheet "Flag Summary": r1r0

wr1 / wr2 base-byte builders: address mode + memory/IO select, no timing byte.

writeBytes copies src into emulated memory starting at addr.

writeDummyMFROM writes an 8KB file filled with the given byte value.

writeTempTAP writes a one-block .tap (flag + data + XOR checksum, with the 2-byte little-endian length prefix) and returns its path.

AddAutosave inserts an automatic snapshot, opens a fresh input recording block at the supplied T-state offset, and runs the pruning policy. The suppli

AddCreator appends a creator block — typically called once at the start of recording so playback tools can identify the producer.