Apple-2-SW/dos33fsprogs
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duet: update comments

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This commit is contained in:
Vince Weaver 2018-05-31 13:27:45 -04:00
parent 25a8d7b497
commit 721e96a864
1 changed files with 38 additions and 25 deletions
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63
electric_duet/duet.s
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@ -23,8 +23,8 @@
.define EQU =
; These are all "Free" zero page locations
LOC6 EQU $06
LOC7 EQU $07
FREQ1 EQU $06
FREQ2 EQU $07
DURATION EQU $08
LOC9 EQU $09
LOC1D EQU $1D
@ -39,10 +39,11 @@ play_ed:
LDA #$01 ; 900: A9 01 ; 2 *!*
STA LOC9 ; 902: 85 09 ; 3
STA LOC1D ; 904: 85 1D ; 3
PHA ; 906: 48 ; 3
PHA ; 907: 48 ; 3
PHA ; 908: 48 ; 3
BNE label1 ; 909: D0 15 ; 4 *!*
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 *!*
label2:
INY ; 90B: C8 ; 2
LDA (MADDRL),Y ; 90C: B1 1E ; 5 *!*
@ -55,41 +56,53 @@ loop:
CLC ; 917: 18 ; 2
ADC #$03 ; 918: 69 03 ; 2 *!*
STA MADDRL ; 91A: 85 1E ; 3
BCC label1 ; 91C: 90 02 ; 4 *!*
BCC load_triplet ; 91C: 90 02 ; 4 *!*
INC MADDRH ; 91E: E6 1F ; 5
label1:
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 label2 ; 926: F0 E3 ; 4 *!* If one ?
BCS play_note ; 928: B0 0D ; 4 *!* If >1, then duration
PLA ; 92A: 68 ; 4 POP
PLA ; 92B: 68 ; 4 POP
PLA ; 92C: 68 ; 4 POP
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
sub1:
LDX #$49 ; 92D: A2 49 ; 2 *!* X=0x49 (EOR opcode)
INY ; 92F: C8 ; 2 increment to next byte
LDA (MADDRL),Y ; 930: B1 1E ; 5 *!* load next byte
BNE label4 ; 932: D0 02 ; 4 *!* if not zero
BNE exit_player ; 932: D0 02 ; 4 *!* if not zero
LDX #$C9 ; 934: A2 C9 ; 2 *!* X=0xC9 (CMP opcode)
label4:
exit_player:
; if byte0==0 and byte1==0 then done playing
RTS ; 936: 60 ; 6 return
; We've got a duration/note/note triplet here
play_note:
STA DURATION ; 937: 85 08 ; 3
JSR sub1 ; 939: 20 2D09 ; 6
STX STARTADDR+$83 ; 93C: 8E 8309 ; 4 self-modify EOR/CMP
STA LOC6 ; 93F: 85 06 ; 3
LDX LOC9 ; 941: A6 09 ; 3 *!*
STA DURATION ; 937: 85 08 ; 3 store out duration
JSR sub1 ; 939: 20 2D09 ; 6 get freq#1
STX STARTADDR+$83 ; 93C: 8E 8309 ; 4 if 0 self-modify EOR/CMP
STA FREQ1 ; 93F: 85 06 ; 3 ??
LDX LOC9 ; 941: A6 09 ; 3 *!* ??
label5:
LSR A ; 943: 4A ; 2
DEX ; 944: CA ; 2
BNE label5 ; 945: D0 FC ; 4 *!*
STA STARTADDR+$7C ; 947: 8D 7C09 ; 4 ; self-modify
JSR sub1 ; 94A: 20 2D09 ; 6
STX STARTADDR+$BB ; 94D: 8E BB09 ; 4 ; self-modify
STA LOC7 ; 950: 85 07 ; 3
JSR sub1 ; 94A: 20 2D09 ; 6 get freq#2
STX STARTADDR+$BB ; 94D: 8E BB09 ; 4 if 0 self-modify EOR/CMP
STA FREQ2 ; 950: 85 07 ; 3
LDX LOC1D ; 952: A6 1D ; 3 *!*
label6:
LSR A ; 954: 4A ; 2
@ -113,8 +126,8 @@ label7:
BIT $C030 ; 96C: 2C 30C0 ; 4 SPEAKER
label9:
STA LOC4E ; 96F: 85 4E ; 3
BIT $C000 ; 971: 2C 00C0 ; 4 KEYBOARD DATA
BMI label4 ; 974: 30 C0 ; 4 *!*
BIT $C000 ; 971: 2C 00C0 ; 4 KEYBOARD DATA
BMI exit_player ; 974: 30 C0 ; 4 *!* if keypress, exit
DEY ; 976: 88 ; 2
BNE label10 ; 977: D0 02 ; 4 *!*
BEQ label11 ; 979: F0 06 ; 4 *!*
@ -123,7 +136,7 @@ label10:
BEQ label12 ; 97D: F0 04 ; 4 *!* !!!
BNE label13 ; 97F: D0 04 ; 4 *!*
label11:
LDY LOC6 ; 981: A4 06 ; 3 *!*
LDY FREQ1 ; 981: A4 06 ; 3 *!*
label12:
EOR #$40 ; 983: 49 40 ; 2 *!* !!!
label13:
@ -164,7 +177,7 @@ label20:
BEQ label22 ; 9B5: F0 04 ; 4 *!* !!!
BNE label23 ; 9B7: D0 04 ; 4 *!*
label21:
LDX LOC7 ; 9B9: A6 07 ; 3 *!*
LDX FREQ2 ; 9B9: A6 07 ; 3 *!*
label22:
EOR #$80 ; 9BB: 49 80 ; 2 *!* !!!
label23: