KN7000 Sequencer

KN7000 Sequencer

The KN7000’s on-board sequencer records and plays back songs — both the player’s own performance and Standard MIDI Files — with a note/step editor, karaoke-style lyrics, and the ability to turn a recorded sequence into a Composer style or a Pad phrase. Like the rest of the UI it runs on the MILK toolkit, so it is decoded here from kn7000_program.rom through its event namespace and its MT_ engine API, both recovered from the firmware’s reflection tables. It sits between the storage layer (which loads/saves the .MID files) and the tone generators that play the notes.

Engine API

The sequencer engine is reached through a dedicated block of MT_* calls (the MILK MT_GetProcedure dispatch — table at program 0x355764). They split into transport/query and rendering groups:

Call	Purpose
MT_Seq_PlayRequest	start playback of the current song
MT_Seq_ChangeColor	recolour the display during playback
MT_GetCurSongName	current song title
MT_GetComporserName	current Composer (style) name
MT_GetLyricsSongName / MT_GetLyricsMusic / MT_GetLyricsLyrics	lyrics data for karaoke display
MT_GetDiskFileName / MT_GetDiskFileNo	the file being loaded/saved
MT_GetInternalData	the in-RAM song buffer

The note/step editor is served by a family of drawing primitives: MT_DrawNote (_0/_1 variants), MT_DrawHilightNote, MT_DrawCursor, MT_DrawMeas_NE / MT_DrawMeas_SR (measure rulers), MT_DrawSoundName / MT_DrawSoundCursor, and the step-edit set MT_StepDataDraw, MT_StepDrawCursor, MT_StepDrawStrData, MT_StepDrawMMMData — i.e. both a piano-roll (“note”) view and a numeric step-list view, ending each frame with MT_SeqDrawEnd.

Event namespace

The sequencer screen has its own EV_* event block (name table at program 0x35570C), separate from the global UI events:

• transport — EV_PlayStartIni, EV_PlayRequest, EV_GetEvent
• display — EV_SEQ_DRAW, EV_ALLCLEAR, EV_ALLDRAW, EV_RENEW, EV_REVERSE, EV_UPDATE_SCREEN, EV_SCROLLUP, EV_ChangeColor, EV_CURSONGNAME
• write / commit — EV_SONGWRITE, EV_COMPORSERWRITE, EV_LYRICSMUSICWRITE, EV_LYRICSLYRICSWRITE
• transpose — EV_SEQ_TRAS_RESET, EV_SEQ_TRAS_UPDATE, EV_SEQ_TRAS_OK_WIN
• file — EV_DISKFILENAME, EV_DISKFILENO

Record / play controls

The recorder and transport are driven by the screen handlers (all recovered by name): track selection SeqTrackSel, measure navigation SeqMeasUpDown, easy record SeqEasyRecOk, cycle (loop) record SeqCycRecTglFunc / SeqPlayCycleTgl / SeqCycClrSwFunc, the metronome toggle SeqRecMetTglFunc, and stop SeqRecStopExec. Lyrics display is handled by SeqLyricsShowHide / SeqLyricsSong and set up by the AP-task helper AppSEQ_InitSmfLyrics — confirming the sequencer engine runs in the AP task (see Tasks & Scheduler) while its screen runs in the main task.

Standard MIDI Files and conversions

Songs interchange as SMF (.MID) through the storage layer: SmfLoadAsFunc / SmfSaveAsFunc / SmfPlayAsFunc, naming/rename via SmfFileNaming / SmfFileRename, and song-slot mapping SmfSeqToSongNumFunc / SmfSeqFromSongNumFunc. A recorded sequence can also be converted in place into other engines’ data — SeqToCmpCopyGrid / Seq2CmpCpEditFunc copy it into a Composer style, and SeqToPadCopyGrid / Seq2PadCpEditFunc copy it into a Pad phrase — which is why the pad presets are themselves stored as MIDI event streams.

The tempo clock (how playback actually advances)

Everything the KN7000 plays in time — the sequencer, the rhythm accompaniment, the metronome, the built-in demos, MIDI clock out — is paced by one on-chip 16-bit hardware timer (mode register 0x34001082, 16-bit reload 0x34001092, counter 0x340010A2). The firmware programs its reload as 1,250,000 ÷ BPM on a 2 MHz timebase (IOCLK 16 MHz ÷ 8), and every underflow raises interrupt group 7, whose handler (0x48447084) is a 96-PPQN tick: it advances a mod-96 beat phase (0x50149664) and steps five clock-lane structures that make queued events due. Tempo changes simply rewrite the reload on the fly (clamped 40–300 BPM). A second timer (0x34001080/90) provides the separate 1 kHz system tick that runs the RTOS scheduler and UI — which is why a machine can have a fully live UI while sequenced playback is stopped.

The ten demo songs are self-contained in the program ROM: per song a zlib-compressed setup blob (track table and initial part programs), a sequence blob (256-byte-per-measure pages of delta-timed, running-status MIDI events) and a sounds blob, plus a text “ACT” script that paces the slideshow from the song position.

In MAME this timer was the last missing link for playback: with it modeled, the demo songs play end-to-end and the rhythm accompaniment starts and runs from START/STOP, at the displayed tempo.

Relationship to the KN5000

The sequencer concept, the MT_Seq_*/EV_* naming and the SMF interchange are shared with the KN5000 (Shared Codebase Map); the Sequencer and Accompaniment engine KN5000 pages are the conceptual companions. The concrete KN7000 specifics observed here are the addresses of the engine API and event tables and the Seq→Composer / Seq→Pad conversion paths.