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duet: more comments

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This commit is contained in:
Vince Weaver 2018-05-31 13:47:04 -04:00
parent 721e96a864
commit 741ab4c1a1
1 changed files with 47 additions and 39 deletions
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86
electric_duet/duet.s
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@ -20,50 +20,54 @@
; Electric Duet Player Routine circa 1980 ; Electric Duet Player Routine circa 1980
; Most comments added by Vince Weaver
.define EQU = .define EQU =
; These are all "Free" zero page locations ; These are all "Free" zero page locations
FREQ1 EQU $06 FREQ1 EQU $06
FREQ2 EQU $07 FREQ2 EQU $07
DURATION EQU $08 DURATION EQU $08
LOC9 EQU $09 INSTRUMENT1 EQU $09
LOC1D EQU $1D INSTRUMENT2 EQU $1D
MADDRL EQU $1E MADDRL EQU $1E
MADDRH EQU $1F MADDRH EQU $1F
LOC4E EQU $4E LOC4E EQU $4E
LOC4F EQU $4F COUNT256 EQU $4F
STARTADDR EQU $0900 STARTADDR EQU $0900
play_ed: play_ed:
LDA #$01 ; 900: A9 01 ; 2 *!* LDA #$01 ; 900: A9 01 ; 2 *!*
STA LOC9 ; 902: 85 09 ; 3 STA INSTRUMENT1 ; 902: 85 09 ; 3 set default
STA LOC1D ; 904: 85 1D ; 3 STA INSTRUMENT2 ; 904: 85 1D ; 3 instruments
PHA ; 906: 48 ; 3 1 on stack PHA ; 906: 48 ; 3 1 on stack
PHA ; 907: 48 ; 3 1 on stack PHA ; 907: 48 ; 3 1 on stack
PHA ; 908: 48 ; 3 1 on stack PHA ; 908: 48 ; 3 1 on stack
BNE load_triplet ; 909: D0 15 ; 4 *!* BNE load_triplet ; 909: D0 15 ; 4 *!* start decoding
label2: change_instrmnt:
INY ; 90B: C8 ; 2 INY ; 90B: C8 ; 2
LDA (MADDRL),Y ; 90C: B1 1E ; 5 *!* LDA (MADDRL),Y ; 90C: B1 1E ; 5 *!* load next byte
STA LOC9 ; 90E: 85 09 ; 3 STA INSTRUMENT1 ; 90E: 85 09 ; 3 save instrument
INY ; 910: C8 ; 2 INY ; 910: C8 ; 2
LDA (MADDRL),Y ; 911: B1 1E ; 5 *!* LDA (MADDRL),Y ; 911: B1 1E ; 5 *!* load next byte
STA LOC1D ; 913: 85 1D ; 3 STA INSTRUMENT2 ; 913: 85 1D ; 3 save instrument
loop:
LDA MADDRL ; 915: A5 1E ; 3 *!* triplet_loop:
CLC ; 917: 18 ; 2 LDA MADDRL ; 915: A5 1E ; 3 *!* increment pointer
CLC ; 917: 18 ; 2 by three
ADC #$03 ; 918: 69 03 ; 2 *!* ADC #$03 ; 918: 69 03 ; 2 *!*
STA MADDRL ; 91A: 85 1E ; 3 STA MADDRL ; 91A: 85 1E ; 3
BCC load_triplet ; 91C: 90 02 ; 4 *!*
INC MADDRH ; 91E: E6 1F ; 5 BCC load_triplet ; 91C: 90 02 ; 4 *!* if overflow
INC MADDRH ; 91E: E6 1F ; 5 update high byte
load_triplet: load_triplet:
LDY #$00 ; 920: A0 00 ; 2 *!* Set Y to zero LDY #$00 ; 920: A0 00 ; 2 *!* Set Y to zero
LDA (MADDRL),Y ; 922: B1 1E ; 5 *!* Load first byte LDA (MADDRL),Y ; 922: B1 1E ; 5 *!* Load first byte
CMP #$01 ; 924: C9 01 ; 2 Compare to 1 CMP #$01 ; 924: C9 01 ; 2 Compare to 1
BEQ label2 ; 926: F0 E3 ; 4 *!* If one ? BEQ change_instrmnt ; 926: F0 E3 ; 4 *!* If one change inst
BCS play_note ; 928: B0 0D ; 4 *!* If >1, then duration BCS play_note ; 928: B0 0D ; 4 *!* If >1, then duration
PLA ; 92A: 68 ; 4 pop off stack PLA ; 92A: 68 ; 4 pop off stack
PLA ; 92B: 68 ; 4 pop off stack PLA ; 92B: 68 ; 4 pop off stack
@ -74,7 +78,7 @@ load_triplet:
; Load byte from music stream ; Load byte from music stream
; Set X=EOR if note zero, set X=CMP if it is ; Set X=EOR if note zero, set X=CMP if it is
sub1: load_freq:
LDX #$49 ; 92D: A2 49 ; 2 *!* X=0x49 (EOR opcode) LDX #$49 ; 92D: A2 49 ; 2 *!* X=0x49 (EOR opcode)
INY ; 92F: C8 ; 2 increment to next byte INY ; 92F: C8 ; 2 increment to next byte
LDA (MADDRL),Y ; 930: B1 1E ; 5 *!* load next byte LDA (MADDRL),Y ; 930: B1 1E ; 5 *!* load next byte
@ -90,31 +94,34 @@ exit_player:
play_note: play_note:
STA DURATION ; 937: 85 08 ; 3 store out duration STA DURATION ; 937: 85 08 ; 3 store out duration
JSR sub1 ; 939: 20 2D09 ; 6 get freq#1 JSR load_freq ; 939: 20 2D09 ; 6 get freq#1
STX STARTADDR+$83 ; 93C: 8E 8309 ; 4 if 0 self-modify EOR/CMP STX STARTADDR+$83 ; 93C: 8E 8309 ; 4 if 0 self-modify EOR/CMP
STA FREQ1 ; 93F: 85 06 ; 3 ?? STA FREQ1 ; 93F: 85 06 ; 3
LDX LOC9 ; 941: A6 09 ; 3 *!* ?? LDX INSTRUMENT1 ; 941: A6 09 ; 3 *!*
label5:
LSR A ; 943: 4A ; 2
DEX ; 944: CA ; 2
BNE label5 ; 945: D0 FC ; 4 *!*
STA STARTADDR+$7C ; 947: 8D 7C09 ; 4 ; self-modify
JSR sub1 ; 94A: 20 2D09 ; 6 get freq#2 instr1_adjust:
LSR A ; 943: 4A ; 2 rshift freq by inst#
DEX ; 944: CA ; 2
BNE instr1_adjust ; 945: D0 FC ; 4 *!*
STA STARTADDR+$7C ; 947: 8D 7C09 ; 4 self-modify a CPY
JSR load_freq ; 94A: 20 2D09 ; 6 get freq#2
STX STARTADDR+$BB ; 94D: 8E BB09 ; 4 if 0 self-modify EOR/CMP STX STARTADDR+$BB ; 94D: 8E BB09 ; 4 if 0 self-modify EOR/CMP
STA FREQ2 ; 950: 85 07 ; 3 STA FREQ2 ; 950: 85 07 ; 3
LDX LOC1D ; 952: A6 1D ; 3 *!* LDX INSTRUMENT2 ; 952: A6 1D ; 3 *!*
label6: instr2_adjust:
LSR A ; 954: 4A ; 2 LSR A ; 954: 4A ; 2 rshift freq by inst#
DEX ; 955: CA ; 2 DEX ; 955: CA ; 2
BNE label6 ; 956: D0 FC ; 4 *!* BNE instr2_adjust ; 956: D0 FC ; 4 *!*
STA STARTADDR+$B4 ; 958: 8D B409 ; 4 ; self-modify STA STARTADDR+$B4 ; 958: 8D B409 ; 4 self modify a CPX
PLA ; 95B: 68 ; 4 PLA ; 95B: 68 ; 4
TAY ; 95C: A8 ; 2 TAY ; 95C: A8 ; 2
PLA ; 95D: 68 ; 4 PLA ; 95D: 68 ; 4
TAX ; 95E: AA ; 2 TAX ; 95E: AA ; 2
PLA ; 95F: 68 ; 4 PLA ; 95F: 68 ; 4
BNE label8 ; 960: D0 03 ; 4 *!* BNE label8 ; 960: D0 03 ; 4 *!*
label99: label99:
BIT $C030 ; 962: 2C 30C0 ; 4 SPEAKER BIT $C030 ; 962: 2C 30C0 ; 4 SPEAKER
label8: label8:
@ -155,8 +162,9 @@ label14:
label16: label16:
CMP $C030 ; 996: CD 30C0 ; 4 SPEAKER CMP $C030 ; 996: CD 30C0 ; 4 SPEAKER
label17: label17:
DEC LOC4F ; 999: C6 4F ; 5 DEC COUNT256 ; 999: C6 4F ; 5 div by 256 counter
BNE label18 ; 99B: D0 11 ; 4 *!* BNE label18 ; 99B: D0 11 ; 4 *!*
DEC DURATION ; 99D: C6 08 ; 5 DEC DURATION ; 99D: C6 08 ; 5
BNE label18 ; 99F: D0 0D ; 4 *!* BNE label18 ; 99F: D0 0D ; 4 *!*
BVC label19 ; 9A1: 50 03 ; 4 *!* BVC label19 ; 9A1: 50 03 ; 4 *!*
@ -167,7 +175,7 @@ label19:
PHA ; 9A8: 48 ; 3 PHA ; 9A8: 48 ; 3
TYA ; 9A9: 98 ; 2 TYA ; 9A9: 98 ; 2
PHA ; 9AA: 48 ; 3 PHA ; 9AA: 48 ; 3
JMP loop ; 9AB: 4C 1509 ; 3 JMP triplet_loop ; 9AB: 4C 1509 ; 3
label18: label18:
DEX ; 9AE: CA ; 2 DEX ; 9AE: CA ; 2
BNE label20 ; 9AF: D0 02 ; 4 *!* BNE label20 ; 9AF: D0 02 ; 4 *!*