AnachronautandClaude Opus 5
5d9b39514b
Order lists hold one-byte sequence indices and 0x80 holds a one-byte patch index. Two tables, PatchTable and SequenceTable, are the only places an address lives. THAT IS WHAT MAKES A TUNE LOADABLE WITHOUT WALKING IT. Nothing inside a sequence or an order list is an address, so putting one in memory means adding the load address to two arrays and nothing else. The alternative is a loader that parses every sequence looking for addresses to correct, which is a loader a malformed file can walk off a cliff. Doing it now, while the tune is still assembled in, means the file form and the assembled form are the same shape - so reading a tune from a file will change no engine code at all. The whole point of the rung. The patch each voice starts on moved from four calls in a row into VoiceStart, four declared bytes, and loadStartPatches reads them. A starting instrument is state and belongs where state goes: the user's ruling is that a voice with undefined state is an error, prompted by noticing that a program run a second time starts with the memory the first run left, because loading is what initialises and running is not. Order lists also halved in size, which was not the reason but is welcome. Hand-writing the two tables is exactly the tedium the compiler exists to remove - every sequence counted into its place, and moving one means renumbering. Better to feel that here than after a tool has baked the shape in. Verified by rendering: bar for bar the same piece. break.sh confirms the scaling, since an index is doubled to reach a two-byte entry and halving that step lands on the wrong sequence and fails four checks. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
159 lines
5.1 KiB
NASM
159 lines
5.1 KiB
NASM
; Four voices on one tick, staggered so that each can be heard on its own.
|
|
;
|
|
; M2 of the music player. What is being checked is that the voices share the tick and NOTHING
|
|
; ELSE: each keeps its own place in its own track and its own count of how long the note it is
|
|
; holding lasts, so one can rest while another plays.
|
|
;
|
|
; Twelve ticks of 125,000 cycles, which is a sixteenth note at 120 beats a minute:
|
|
;
|
|
; ticks 0-3 voice 0 plays middle C voice 1 rests
|
|
; ticks 4-7 voice 0 rests voice 1 plays the C above it
|
|
; ticks 8-11 voice 0 plays middle C voice 1 plays the C above it
|
|
;
|
|
; BOTH VOICES ARE ASKED FOR NOTE 60. The octave between them is in their patches, which is
|
|
; M3: a patch belongs to its channel, so four of them can be up at once. Under a device where
|
|
; it did not, the second patch loaded would own both voices and they would sound in unison.
|
|
;
|
|
; So the first two windows have one voice in them and can be measured for pitch, and the third
|
|
; has both and can be measured for level. Two voices sounding at once cannot be asked their
|
|
; pitch - a crossing counter given two notes answers with neither.
|
|
;
|
|
; THIS IS DELIBERATELY NOT Apps/Play.asm. It shares the design and not the code, and it is
|
|
; smaller: no track ever ends here, so there is no live flag and no count of what is still
|
|
; playing. What it has is the part worth pinning - a cursor and a countdown per voice, moved
|
|
; with LDD and STD.
|
|
;
|
|
; Written by Anachronaut
|
|
|
|
#Program
|
|
|
|
start:
|
|
; A patch each, in the format SoundPatch writes: a count and that many pairs. They differ in
|
|
; ONE parameter - the octave - and VoiceStart gives the low one to voice 0 and the high one
|
|
; to voice 1. If a patch belonged to the device rather than to its channel the second would
|
|
; overwrite the first and both voices would sound the same.
|
|
CALL loadStartPatches
|
|
|
|
INIA 0x60
|
|
OUTA 0x46
|
|
|
|
; 125,000 cycles a tick. The period before the control byte, because writing control with
|
|
; the run bit set is what loads it.
|
|
INIA 0x01
|
|
OUTA 0x52
|
|
INIA 0xE8
|
|
OUTA 0x53
|
|
INIA 0x48
|
|
OUTA 0x54
|
|
INIA 0x07
|
|
OUTA 0x51
|
|
SIF
|
|
|
|
; Sixteen ticks. B survives the calls below, because a CALL saves it.
|
|
INIB 0d16
|
|
tickLoop:
|
|
SETD.1 Voice0
|
|
RSTA
|
|
CALL stepVoice
|
|
SETD.1 Voice1
|
|
INIA 0d1
|
|
CALL stepVoice
|
|
DECB
|
|
BRB lastTick
|
|
WAIT
|
|
BRI tickLoop
|
|
|
|
lastTick:
|
|
; The last step started a note and nothing has waited for it yet. Without this the final
|
|
; tick is never rendered, and a window measuring it runs off the end of the samples.
|
|
WAIT
|
|
|
|
done:
|
|
CIF
|
|
RSTA
|
|
OUTA 0x51
|
|
HALT
|
|
|
|
tick:
|
|
RETI
|
|
|
|
#Data
|
|
|
|
; Middle C, then out of the way, then back - against the octave above doing the opposite.
|
|
; ---- The order lists, and what they are for ----
|
|
;
|
|
; Four bars of four ticks each, and the SAME TWO SEQUENCES do nearly all of it. Beat is used
|
|
; twice by voice 0 and twice by voice 1 - four placings of one phrase, written once, and on
|
|
; two different voices, because the voice is a property of where a sequence is placed and not
|
|
; of the sequence.
|
|
;
|
|
; ticks 0-3 4-7 8-11 12-15
|
|
; voice 0 Beat Quiet Beat Switch
|
|
; voice 1 Quiet Beat Beat (its order list ends here)
|
|
Order0:
|
|
0d0 0d1 0d0 0d2 0d3 0xFF
|
|
Order1:
|
|
0d1 0d0 0d0 0xFF ; And this one ENDS, so the last bar has voice 1 stopped rather
|
|
; than resting. A player that missed the terminator would read
|
|
; whatever follows as a sequence index and play it.
|
|
Order2:
|
|
0d3 0xFF
|
|
Order3:
|
|
0d3 0xFF
|
|
|
|
PatchTable:
|
|
PatchLow PatchHigh
|
|
|
|
SequenceTable:
|
|
Beat Quiet Switch Tail ; 0 to 3
|
|
|
|
VoiceStart:
|
|
0d0 0d1 0d0 0d0
|
|
|
|
Beat:
|
|
0d60 0d4 ; Note 60 on both voices. The octave between them is their patches.
|
|
0xFF
|
|
Quiet:
|
|
0d00 0d4
|
|
0xFF
|
|
Switch:
|
|
0x80 0d1 ; Voice 0 takes patch one, which is voice 1's, mid-piece.
|
|
0d60 0d4 ; The same note number it has played all along.
|
|
0xFF
|
|
Tail:
|
|
0d00 0xFF ; Long enough that nothing runs off the end of its order list.
|
|
0xFF
|
|
|
|
; Seven pairs each, and only the last of them differs: the octave, centred on 128. So the two
|
|
; voices below are asked for THE SAME NOTE NUMBER and answer an octave apart, which nothing
|
|
; but a patch of their own could do.
|
|
PatchLow:
|
|
0d8
|
|
0x00 0d2 ; Saw
|
|
0x01 0xFF ; at full gain
|
|
0x05 0d1 ; and switched on.
|
|
0x20 0d0 ; No attack
|
|
0x21 0d0 ; no decay
|
|
0x22 0xFF ; and held at full, so a note lasts exactly its ticks
|
|
0x23 0d5 ; and goes quickly when the gate drops, which the windows below
|
|
; depend on: a note still fading into the next voice's stretch is
|
|
; a second pitch in it, and a crossing counter given two answers
|
|
; with neither.
|
|
0x04 0d128 ; Octave, centred.
|
|
PatchHigh:
|
|
0d8
|
|
0x00 0d2
|
|
0x01 0xFF
|
|
0x05 0d1
|
|
0x20 0d0
|
|
0x21 0d0
|
|
0x22 0xFF
|
|
0x23 0d5
|
|
0x04 0d129 ; And this one an octave up.
|
|
|
|
#Include player.asm
|
|
|
|
#Vectors
|
|
Boot start
|
|
Device 0x50 tick
|