mirror of
https://github.com/sehugg/8bitworkshop.git
synced 2024-11-25 18:33:11 +00:00
253 lines
5.6 KiB
Plaintext
253 lines
5.6 KiB
Plaintext
|
|
processor 6502
|
|
include "vcs.h"
|
|
include "macro.h"
|
|
include "xmacro.h"
|
|
|
|
org $f000
|
|
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
;
|
|
; This program demonstrates a VCS music player based on tracks
|
|
; and patterns. A pattern is a list of variable-length notes,
|
|
; each of which is defined by a pitch and duration.
|
|
; There are two tracks, one for each audio channel.
|
|
; Each track consists of a list of patterns, each entry being
|
|
; a byte offset into the Patterns array.
|
|
;
|
|
; The patterns in the tracks are played in-order until one ends,
|
|
; and then both tracks are restarted. It's up to the composer
|
|
; to make sure the durations in each track line up properly.
|
|
;
|
|
; Patterns consist of NOTE or TONE commands. TONE sets the
|
|
; tone of the channel (the AUDCx register) and NOTE plays a note
|
|
; with a duration taken from a lookup table.
|
|
; TONE 0 ends a pattern.
|
|
;
|
|
; Both channels share the same logical array for tracks and patterns,
|
|
; so both tracks can take up to 255 bytes total, and all patterns
|
|
; can use up to 255 bytes total.
|
|
; The music player uses 8 bytes of RAM (not counting stack).
|
|
;
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
|
|
Trk0idx equ $e0 ; offset into tracks for channel 0
|
|
Trk1idx equ $e1 ; offset into tracks for channel 1
|
|
Pat0idx equ $e2 ; offset into patterns for channel 0
|
|
Pat1idx equ $e3 ; offset into patterns for channel 1
|
|
Chan0dur equ $e4 ; current note duration channel 0
|
|
Chan1dur equ $e5 ; current note duration channel 1
|
|
Chan0note equ $e6 ; current note pitch channel 0
|
|
Chan1note equ $e7 ; current note pitch channel 1
|
|
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
; Usage: NOTE pitch duration
|
|
; Plays a note in a pattern.
|
|
; pitch = 0-31
|
|
; duration = 1-7, uses DurFrames lookup table
|
|
MAC NOTE
|
|
.pitch SET {1}
|
|
.durat SET {2}
|
|
.byte (.pitch+(.durat<<5))
|
|
ENDM
|
|
|
|
; Usage: TONE tone
|
|
; Changes the tone in a pattern.
|
|
; tone = 1-15
|
|
MAC TONE
|
|
.tone SET {1}
|
|
.byte .tone
|
|
ENDM
|
|
|
|
; Usage: PATTERN address
|
|
; Plays a pattern in a track.
|
|
MAC PATTERN
|
|
.addr SET {1}
|
|
.byte (.addr-Patterns)
|
|
ENDM
|
|
|
|
; Usage: ENDTRACK
|
|
; Marks the end of a track.
|
|
MAC ENDTRACK
|
|
.byte 0
|
|
ENDM
|
|
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
|
|
Start
|
|
CLEAN_START
|
|
jsr ResetTrack
|
|
|
|
NextFrame
|
|
VERTICAL_SYNC
|
|
TIMER_SETUP 37
|
|
ldx #0
|
|
jsr MusicFrame
|
|
ldx #1
|
|
jsr MusicFrame
|
|
TIMER_WAIT
|
|
TIMER_SETUP 192
|
|
TIMER_WAIT
|
|
TIMER_SETUP 29
|
|
TIMER_WAIT
|
|
jmp NextFrame
|
|
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
|
|
ResetTrack
|
|
lda #0
|
|
sta Trk0idx
|
|
sta Pat0idx
|
|
sta Pat1idx
|
|
sta Chan0dur
|
|
sta Chan1dur
|
|
lda #Track1-Track0
|
|
sta Trk1idx
|
|
NextPattern
|
|
ldy Trk0idx,x
|
|
lda Track0,y
|
|
beq ResetTrack
|
|
sta Pat0idx,x
|
|
inc Trk0idx,x
|
|
MusicFrame
|
|
dec Chan0dur,x ; decrement note duration
|
|
bpl PlayNote ; only load if duration < 0
|
|
TryAgain
|
|
ldy Pat0idx,x ; load index into pattern table
|
|
lda Patterns,y ; load pattern code
|
|
beq NextPattern ; end of pattern?
|
|
inc Pat0idx,x ; increment pattern index for next time
|
|
pha ; save A for later
|
|
clc ; clear carry for ROL
|
|
rol
|
|
rol
|
|
rol
|
|
rol ; rotate A left by 4 (same as ROR by 5)
|
|
and #7 ; only take top 3 bits
|
|
beq NoteTone ; duration zero? tone instruction
|
|
tay ; Y = duration
|
|
lda DurFrames,y ; look up in duration table
|
|
sta Chan0dur,x ; save note duration
|
|
pla ; pop saved value into A
|
|
and #$1f ; extract first 5 bits
|
|
sta Chan0note,x ; store as note value
|
|
PlayNote
|
|
lda Chan0note,x ; get note pitch for channel
|
|
sta AUDF0,x ; store frequency register
|
|
lda Chan0dur,x ; get note duration remaining
|
|
clc
|
|
ror ; divide by 2
|
|
cmp #16
|
|
bcc NoHighVol
|
|
lda #15 ; make sure no greater than 15 (max)
|
|
NoHighVol
|
|
sta AUDV0,x ; store volume register
|
|
rts
|
|
; This routine is called for duration 0 (TONE) codes
|
|
NoteTone
|
|
pla
|
|
and #$f
|
|
beq NextPattern
|
|
sta AUDC0,x
|
|
jmp TryAgain
|
|
|
|
|
|
Patterns
|
|
TONE 0 ; byte 0 of patterns array is unused
|
|
|
|
Pattern00
|
|
TONE 3
|
|
NOTE 16,4
|
|
NOTE 2,4
|
|
NOTE 16,4
|
|
NOTE 30,4
|
|
NOTE 16,4
|
|
NOTE 4,4
|
|
NOTE 30,4
|
|
NOTE 16,4
|
|
TONE 0
|
|
|
|
Pattern10
|
|
TONE 6
|
|
NOTE 6,4
|
|
TONE 12
|
|
NOTE 16,4
|
|
NOTE 18,4
|
|
NOTE 19,4
|
|
NOTE 22,4
|
|
NOTE 23,4
|
|
NOTE 26,4
|
|
NOTE 23,4
|
|
NOTE 26,4
|
|
NOTE 23,4
|
|
NOTE 26,4
|
|
NOTE 23,4
|
|
NOTE 22,6
|
|
TONE 0
|
|
Pattern11
|
|
TONE 6
|
|
NOTE 6,6
|
|
NOTE 6,4
|
|
TONE 12
|
|
NOTE 16,4
|
|
NOTE 18,4
|
|
NOTE 19,4
|
|
NOTE 22,4
|
|
NOTE 23,4
|
|
NOTE 26,4
|
|
NOTE 23,4
|
|
NOTE 26,4
|
|
NOTE 26,4
|
|
NOTE 22,7
|
|
TONE 11
|
|
NOTE 0,7
|
|
NOTE 0,2
|
|
TONE 0
|
|
Pattern12
|
|
TONE 11
|
|
NOTE 0,5
|
|
TONE 12
|
|
NOTE 18,5
|
|
NOTE 18,3
|
|
NOTE 18,5
|
|
NOTE 16,6
|
|
NOTE 19,5
|
|
NOTE 22,3
|
|
TONE 6
|
|
NOTE 4,5
|
|
NOTE 4,4
|
|
TONE 12
|
|
NOTE 11,5
|
|
NOTE 11,3
|
|
NOTE 11,5
|
|
NOTE 10,6
|
|
NOTE 10,4
|
|
NOTE 17,3
|
|
NOTE 17,5
|
|
NOTE 16,5
|
|
TONE 0
|
|
|
|
Track0
|
|
PATTERN Pattern00
|
|
PATTERN Pattern00
|
|
PATTERN Pattern00
|
|
PATTERN Pattern00
|
|
PATTERN Pattern00
|
|
PATTERN Pattern00
|
|
PATTERN Pattern12
|
|
ENDTRACK
|
|
Track1
|
|
PATTERN Pattern10
|
|
PATTERN Pattern11
|
|
PATTERN Pattern10
|
|
PATTERN Pattern12
|
|
ENDTRACK
|
|
|
|
DurFrames
|
|
.byte 0,4,8,12,16,24,32,48
|
|
|
|
; Epilogue
|
|
org $fffc
|
|
.word Start
|
|
.word Start
|