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pt3_lib: merge in fix for when more than 42 patterns

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to look up pattern you take the number, and multiply by 3 because
there are 3 channels then by two as it's a 16-bit pointer.

43*3=129 and when you multiply by two it overflows 8-bit register

hit this bug with the pt3 found in the second reality demo

this fix isn't really optimal but seems to work
This commit is contained in:
Vince Weaver 2024-01-17 18:54:21 -05:00
parent d4219e75e3
commit cb0546ede7
1 changed files with 35 additions and 5 deletions
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40
music/pt3_lib/pt3_lib_core.s
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@ -1564,18 +1564,48 @@ not_done:
; set up the three pattern address pointers
asl ; mul pattern offset by two, as word sized ; 2
tay ; 2
; BUG BUG BUG
; pattern offset can be bigger than 128, and if we multiply
; by two to get word size it will overflow
; for example I have a .pt3 where pattern #48 ($30*3=$90) is used
; asl ; mul pattern offset by two, as word sized ; 2
; tay ; 2
; point PATTERN_H/PATTERN_L to the pattern address table
clc ; 2
lda PT3_LOC+PT3_PATTERN_LOC_L ; 4
sta PATTERN_L ; 3
; clc ; 2
; lda PT3_LOC+PT3_PATTERN_LOC_L ; 4
; sta PATTERN_L ; 3
; lda PT3_LOC+PT3_PATTERN_LOC_H ; 4
; adc #>PT3_LOC ; assume page boundary ; 2
; sta PATTERN_H ; 3
clc
sta PATTERN_L
adc PT3_LOC+PT3_PATTERN_LOC_L
php ; save carry as we might generate two
clc
adc PATTERN_L
sta PATTERN_L
lda PT3_LOC+PT3_PATTERN_LOC_H ; 4
adc #>PT3_LOC ; assume page boundary ; 2
plp ; restore carry
adc #0
sta PATTERN_H ; 3
; clc
; tya
; adc PATTERN_L
; adc PATTERN_L
; sta PATTERN_L
; lda #0
; adc PATTERN_H
; sta PATTERN_H
ldy #0
; First 16-bits points to the Channel A address
lda (PATTERN_L),Y ; 5+
sta note_a+NOTE_ADDR_L ; 4