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dos33fsprogs/games/peasant/duet.s

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; ***************************************************************************
; * Copyright (C) 1979-2015 by Paul Lutus *
; * http://arachnoid.com/administration *
; * *
; * This program is free software; you can redistribute it and/or modify *
; * it under the terms of the GNU General Public License as published by *
; * the Free Software Foundation; either version 2 of the License, or *
; * (at your option) any later version. *
; * *
; * This program is distributed in the hope that it will be useful, *
; * but WITHOUT ANY WARRANTY; without even the implied warranty of *
; * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
; * GNU General Public License for more details. *
; * *
; * You should have received a copy of the GNU General Public License *
; * along with this program; if not, write to the *
; * Free Software Foundation, Inc., *
; * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. *
; ***************************************************************************
; 645d roughly trogdor music
; Electric Duet Player Routine circa 1980
; Formatting / comments added by Vince Weaver
; These are all "Free" zero page locations
;FREQ1 = $10
;FREQ2 = $11
;DURATION = $12
;INSTRUMENT1 = $13
;INSTRUMENT2 = $14
;MADDRL = $15
;MADDRH = $16
;LOC4E = $4E
;COUNT256 = $4F
play_ed:
lda #$01 ; 900: A9 01 ; 2 *!*
sta INSTRUMENT1 ; 902: 85 09 ; 3 set default
sta INSTRUMENT2 ; 904: 85 1D ; 3 instruments
pha ; 906: 48 ; 3 1 on stack
pha ; 907: 48 ; 3 1 on stack
pha ; 908: 48 ; 3 1 on stack
bne load_triplet ; 909: D0 15 ; 4 *!* start decoding
change_instrmnt:
iny ; 90B: C8 ; 2
lda (MADDRL),Y ; 90C: B1 1E ; 5 *!* load next byte
sta INSTRUMENT1 ; 90E: 85 09 ; 3 save instrument
iny ; 910: C8 ; 2
lda (MADDRL),Y ; 911: B1 1E ; 5 *!* load next byte
sta INSTRUMENT2 ; 913: 85 1D ; 3 save instrument
triplet_loop:
; flash different if trogdor music
ldy #2
lda (MADDRL),Y
cmp #24 ; D4
beq no_trogdor
bit PAGE2
jmp done_duet_trog
no_trogdor:
bit PAGE1
done_duet_trog:
lda MADDRL ; 915: A5 1E ; 3 *!* increment pointer
clc ; 917: 18 ; 2 by three
adc #$03 ; 918: 69 03 ; 2 *!*
sta MADDRL ; 91A: 85 1E ; 3
bcc load_triplet ; 91C: 90 02 ; 4 *!* if overflow
inc MADDRH ; 91E: E6 1F ; 5 update high byte
load_triplet:
ldy #$00 ; 920: A0 00 ; 2 *!* Set Y to zero
lda (MADDRL),Y ; 922: B1 1E ; 5 *!* Load first byte
cmp #$01 ; 924: C9 01 ; 2 Compare to 1
beq change_instrmnt ; 926: F0 E3 ; 4 *!* If one change inst
bcs play_note ; 928: B0 0D ; 4 *!* If >1, then duration
pla ; 92A: 68 ; 4 pop off stack
pla ; 92B: 68 ; 4 pop off stack
pla ; 92C: 68 ; 4 pop off stack
; fallthrough if first byte was zero
; Load byte from music stream
; Set X=EOR if note zero, set X=CMP if it is
load_freq:
ldx #$49 ; 92D: A2 49 ; 2 *!* X=0x49 (EOR opcode)
iny ; 92F: C8 ; 2 increment to next byte
lda (MADDRL),Y ; 930: B1 1E ; 5 *!* load next byte
bne exit_player ; 932: D0 02 ; 4 *!* if not zero
ldx #$C9 ; 934: A2 C9 ; 2 *!* X=0xC9 (CMP opcode)
exit_player:
; if byte0==0 and byte1==0 then end (I have no idea how)
rts ; 936: 60 ; 6 return
; We've got a duration/note/note triplet here
play_note:
sta DURATION ; 937: 85 08 ; 3 store out duration
jsr load_freq ; 939: 20 2D09 ; 6 get freq#1
stx selfmodify1 ; 93C: 8E 8309 ; 4 if 0 self-modify EOR/CMP
sta FREQ1 ; 93F: 85 06 ; 3
ldx INSTRUMENT1 ; 941: A6 09 ; 3 *!*
instr1_adjust:
lsr A ; 943: 4A ; 2 rshift freq by inst#
dex ; 944: CA ; 2
bne instr1_adjust ; 945: D0 FC ; 4 *!*
sta selfmodify2+1 ; 947: 8D 7C09 ; 4 self-modify a CPY
jsr load_freq ; 94A: 20 2D09 ; 6 get freq#2
stx selfmodify3 ; 94D: 8E BB09 ; 4 if 0 self-modify EOR/CMP
sta FREQ2 ; 950: 85 07 ; 3
ldx INSTRUMENT2 ; 952: A6 1D ; 3 *!*
instr2_adjust:
lsr A ; 954: 4A ; 2 rshift freq by inst#
dex ; 955: CA ; 2
bne instr2_adjust ; 956: D0 FC ; 4 *!*
sta selfmodify4+1 ; 958: 8D B409 ; 4 self modify a CPX
pla ; 95B: 68 ; 4
tay ; 95C: A8 ; 2
pla ; 95D: 68 ; 4
tax ; 95E: AA ; 2
pla ; 95F: 68 ; 4
bne label8 ; 960: D0 03 ; 4 *!*
label99:
bit $C030 ; 962: 2C 30C0 ; 4 SPEAKER
label8:
cmp #$00 ; 965: C9 00 ; 2
bmi label7 ; 967: 30 03 ; 4 *!*
nop ; 969: EA ; 2
bpl label9 ; 96A: 10 03 ; 4 *!*
label7:
bit $C030 ; 96C: 2C 30C0 ; 4 SPEAKER
label9:
sta LOC4E ; 96F: 85 4E ; 3
bit $C000 ; 971: 2C 00C0 ; 4 KEYBOARD DATA
bmi exit_keypress ; 974: 30 C0 ; 4 *!* if keypress, exit
dey ; 976: 88 ; 2
bne selfmodify2 ; 977: D0 02 ; 4 *!*
beq label11 ; 979: F0 06 ; 4 *!*
selfmodify2:
cpy #$00 ; 97B: C0 00 ; 2
beq selfmodify1 ; 97D: F0 04 ; 4 *!* !!!
bne label13 ; 97F: D0 04 ; 4 *!*
label11:
ldy FREQ1 ; 981: A4 06 ; 3 *!*
selfmodify1:
eor #$40 ; 983: 49 40 ; 2 *!* !!!
label13:
bit LOC4E ; 985: 24 4E ; 3
bvc label14 ; 987: 50 07 ; 4 *!*
bvs label15 ; 989: 70 00 ; 4 *!*
label15:
bpl label16 ; 98B: 10 09 ; 4 *!*
nop ; 98D: EA ; 2
bmi label17 ; 98E: 30 09 ; 4 *!*
label14:
nop ; 990: EA ; 2
bmi label16 ; 991: 30 03 ; 4 *!*
nop ; 993: EA ; 2
bpl label17 ; 994: 10 03 ; 4 *!*
label16:
cmp $C030 ; 996: CD 30C0 ; 4 SPEAKER
label17:
dec COUNT256 ; 999: C6 4F ; 5 div by 256 counter
bne label18 ; 99B: D0 11 ; 4 *!*
dec DURATION ; 99D: C6 08 ; 5
bne label18 ; 99F: D0 0D ; 4 *!*
bvc label19 ; 9A1: 50 03 ; 4 *!*
bit $C030 ; 9A3: 2C 30C0 ; 4 SPEAKER
label19:
pha ; 9A6: 48 ; 3
txa ; 9A7: 8A ; 2
pha ; 9A8: 48 ; 3
tya ; 9A9: 98 ; 2
pha ; 9AA: 48 ; 3
jmp triplet_loop ; 9AB: 4C 1509 ; 3
label18:
dex ; 9AE: CA ; 2
bne selfmodify4 ; 9AF: D0 02 ; 4 *!*
beq label21 ; 9B1: F0 06 ; 4 *!*
selfmodify4:
cpx #$00 ; 9B3: E0 00 ; 2
beq selfmodify3 ; 9B5: F0 04 ; 4 *!* !!!
bne label23 ; 9B7: D0 04 ; 4 *!*
label21:
ldx FREQ2 ; 9B9: A6 07 ; 3 *!*
selfmodify3:
eor #$80 ; 9BB: 49 80 ; 2 *!* !!!
label23:
bvs label99 ; 9BD: 70 A3 ; 4 *!*
nop ; 9BF: EA ; 2
bvc label8 ; 9C0: 50 A3 ; 4 *!*
exit_keypress:
inc duet_done
rts
duet_done:
.byte $00
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