scaleToWindowSize maps a percentage (100/125/150/200/300) to the fyne window size. The returned height is padded by the menu-bar height so the emulato

selectRow returns the IN high byte that selects exactly one matrix row.

setLineInterrupt programs the line-interrupt target (OUT 0xF9). Lines 0-191 fire the maskable INT a second time at (line+68)·384; >=192 disables it. T

tapeLoadingActive reports whether a tape is mid-load (playing with blocks still to load) — the window in which fast-tape turbo applies.

installTapeTrap installs a fast-load trap on the CPU that intercepts the 48K ROM LD-BYTES routine at 0x0556 and synthesises the load directly from the

timerExpired: tx_timer(PRESCALER_BITS-1 downto 1) == 0, i.e. timer in {0,1} (uart_tx.vhd:131).

updatePaging resolves the four section read/write pointers from the registers.

Spec-derived tests for NextReg write handlers. Each test pins a code path that exists in the canonical FPGA VHDL at `_tools/reference/tbblue-fpga/cor

xorChecksum returns the standard tape block checksum: the XOR of every byte (flag through last data byte).

AddFileToFAT32 inserts data as a file named fileName under the directory dirPath (e.g. "imported", or "games/imported") into an existing in-memory FAT

AutosaveDue reports whether enough frames have elapsed since the last automatic snapshot to warrant a new one. Drivers call this after each StoreFrame

DistroURL returns the configured distro download URL.

Duration returns the T-state cost of the most recent transfer (per-byte cycle cost × bytes moved). The emulator charges this to the CPU clock so a con

EnableInterface1 turns on the Sinclair Interface 1 — the same path the GUI takes when the user clicks "Enable Interface 1". Pulls the embedded if1-2.r

EnableInterface1 attaches an Interface 1 with the supplied ROM image bytes. Allowed only on the 48K Spectrum.

EnableKempstonMouse attaches a Kempston mouse to the peripheral bus. The mouse is idle until Move / SetButton calls arrive from the host event loop. I

FindAtOrBefore returns the latest entry whose insn ≤ target, or nil if none. Used by tt-rewind to pick the snapshot to restore.

FormatLine produces a one-line description suitable for the breakpoints list in either the telnet `list-breakpoints` output or the visual breakpoints

GetROMManager returns the ROM manager

GetTracer returns the currently-installed TraceFunc (or nil). Used by chained-tracer patterns so a new caller can wrap the existing tracer rather than

GetVariantName returns a human-readable name for the variant

HasPriority reports whether the Layer 2 priority bit (NR$44 bit 7, the high priority bit) is set — i.e. this pixel is promoted above the lower layers

Is80Col reports whether NR$6B bit 6 (80-column mode) is set. In that mode the tilemap is 80 tiles × 8px = 640 pixels wide, so the caller must render i

IsInhibited reports whether the DISCiPLE is inhibited.

KempstonMouseButton presses or releases a Kempston mouse button. btn is the button index (0 = right, 1 = left).

LineHeight returns the active framebuffer height (192 for 256×192, else 256).

List satisfies BreakpointsStore (alias of Snapshot).

Load reads config.json. If the file does not exist (fresh install) it returns a zero Config and no error. A corrupt file returns an error so the calle

LoadImage wraps a raw .TRD dump, inferring 80/40-track and single/double-sided geometry from its length. The 327680-byte size is ambiguous (40-track D

LoadMicrodrive parses a .mdr cartridge file from disk and inserts it into the IF1's drive `which` (0-based). Mirrors the shape of LoadPlus3Disk so the

MicrodriveWriteProtected reports whether the cartridge in drive `which` is currently write-protected. Returns false if the slot is empty or the IF1 is

MixedLevel returns the mean of the four channel levels as an 8-bit unsigned value. The mixer in pkg/ula uses this to fold DAC output into the global a

New returns a hard-reset channel (equivalent to holding i_reset).

NewPageMapWidget builds a fresh diagram bound to mem. Pass a non-nil NextProvider to enable the 8-slot view; passing nil leaves the diagram in 4-slot

OnTop reports whether NR$6B bit 0 (tm_on_top) is set. When on, the FPGA renders the tilemap as ALWAYS opaque over every layer below — even nibble-0 pi

Open opens a file under the mount root. esxDOS flags: bit 0 = read, bit 1 = write, bit 2 = create (if missing), bit 4 = truncate.

PageOut unmaps the shadow ROM, restoring access to the main Spectrum ROM. Called when the IF1 ROM finishes its current command and returns control to

Read fills buf and returns the number of bytes read; for files, this advances the file cursor.

ReadEmbeddedROM reads a ROM file from the embedded filesystem. Returns the data and nil error on success, or nil and an error if not found.

ReadFile reads a .mdr file from disk and parses it.

ReadSector returns a copy of the sector at (cyl, head, sector), or false if the address is out of range.

Refresh recomputes the selected analysis from the live ring.

Reset clears all four DAC levels to 0 and the event-timing state.

RestorePagingState restores a previously saved paging configuration. If state is nil or was never saved, this is a no-op.

Rollback removes everything after the LAST snapshot block in the recording, returning that snapshot. The recording is left ready to resume from that p

RunFrame executes approximately one 50 Hz frame, stepping the CPU and driving the ZX8x interrupts from a T-state line clock. The maskable INT (once pe

SaveTZX writes the currently loaded blocks back to a TZX file. Each block is emitted using the same TZX block-ID it parsed as on load: standard-speed

Seek sets the file cursor relative to whence (0 = start, 1 = current, 2 = end).

SeekToBlock positions the tape at the given block index. Playback is stopped (the caller can call Play afterwards). Out-of-range indices are clamped t

SelectRegister latches the register that will be read or written via the data port. Only the low 4 bits are significant.

SetBetaActive forces the Beta ROM paging state (used by save-state restore). It is a no-op unless the Beta ROM has been enabled.

SetClip installs the sprite clip window (NextReg $19 coords X1,X2,Y1,Y2). X is in 2-pixel units (matching the FPGA), Y in 1-pixel units.

SetDFFD applies a write to port $DFFD, the Spectrum Next high RAM-bank extension. Bits 3:0 are the most-significant bits of the $C000-slot RAM bank se

SetNextDMA installs the Spectrum Next zxnDMA controller. Port 0x6B writes are forwarded as command bytes. Passing nil unhooks.

SetNextDivMMC installs the divMMC pager's port-write hook so OUT (0xE3) reaches it. The pager itself is also wired via the CPU M1 pre-fetch hook (for

SetNextSpritePort installs the sprite engine's $303B select/status port handler. Passing nil unhooks.

SetPeripherals sets the peripheral manager for I/O port delegation

SetROMBank changes which of the four 16K ROM banks is visible at 0x0000-0x3FFF. Called from the NextReg 0x8E handler. Writes through to port7FFD bit 4

SetRender swaps the frame source and repaints.

SetSDHC toggles the OCR's CCS bit so this card advertises SDHC/SDXC capacity (block-addressed CMD17 args) instead of the default SDSC (byte-addressed)

SetScrollX installs the 9-bit Layer 2 X scroll (NR$71 bit0 || NR$16). Only the low 9 bits are kept. Feeds the FPGA address generator (layer2.vhd:152).

SetSide selects the head (0/1) — driven from the SAM port address bit 2.

SetSpecDrum / SetCovox enable or disable each device.

SetTransparency installs the palette index that should be treated as "see-through" for the Layer 2 layer.

SimulateNMI manually triggers an NMI (for testing or programmatic use)

TStatesPerLineFor returns the documented T-states-per-scanline for a machine model: 224 for the 48K (312 lines * 224 = 69888 T-states/frame), 228 for

Tick advances the channel by exactly one i_CLK rising edge with i_iowr = 0.

Wide reports whether this history's entries carry BC/DE/HL/IX/IY.

WireContentionDisable installs the NextReg 0x08 OnWrite handler. NextReg 0x08 is officially "Peripheral 3" and exposes multiple behaviour bits (port-F

WireLayer2 installs the NextReg 0x12 / 0x13 / 0x69 OnWrite handlers. 0x12 / 0x13 select the active / shadow framebuffer banks; 0x69 bit 7 enables Laye

WireLayerPriority installs the NextReg 0x15 OnWrite/OnRead handlers. The compositor reads p.Get() to drive the 5-source ordering rules from the NextRe

Other subsystems (CPU speed at NextReg 0x07, palette at 0x40–0x44, etc.) have their own Wire* functions below; this one is scoped to just the MMU regi

WireSprites installs the NextReg sprite-select (0x34), attribute-byte (0x35-0x39), and auto-incrementing attribute (0x75-0x79) handlers. NR$35-$39 wr

Write9 stores both bytes of a 9-bit palette value (NextReg 0x44 behaviour: two consecutive writes — first the high 8 bits, then the second byte carryi

WriteBlock writes 512 bytes into the image at the given LBA. Returns an error if the source is read-only.

Helper functions for register pairs

applyForcedCPUSpeed enforces the user's "CPU Speed" override (cpuSpeedForce) on the live CPU. Called once per executed frame: - Auto (0), no CPU, or a

banks returns a freshly-constructed accessor for the current emulator. Kept allocation-light because every debugger command builds one — these are tin

bitSet sets bit i in the bitmap.

bpset returns the shared breakpoint store, lazily allocating one if unset. Production always pre-sets d.bps in newRemoteDebugger (before any goroutine

ccfRun runs CCF starting from given A and F.

classifyBranch sets c.BranchSource / c.BranchFrom based on the just-executed instruction's opcode if the PC took an unexpected path. The classifier is

clutColour resolves a 4-bit CLUT index → its master-palette colour.

cmdClearTp removes one tracepoint (by PC) or all if no arg.

cmdTp adds a tracepoint at PC. The CPU does NOT halt at PC; instead, an slog.Info("tp-hit") record is emitted with full register state every time PC f

configureClassicIntTiming sets the maskable frame interrupt to the hardware-faithful narrow pulse for 128K-family models, replacing the legacy "held f

crc16CCITT computes the SD data-block CRC: CRC-16/CCITT with polynomial 0x1021 and initial value 0x0000 (the "XMODEM" variant the SD Physical Layer sp

currentTrack returns the track at the current US / HD / PCN, or nil if the selected drive has no disk in it.

DAA (Decimal Adjust Accumulator) implementation