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megaload: patch on fly to use current disk slot

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This commit is contained in:
Vince Weaver 2018-10-30 12:28:25 -04:00
parent 56598f4196
commit cab24e9717
1 changed files with 42 additions and 15 deletions
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57
megademo/megaload.s
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@ -3,6 +3,7 @@
; TODO:
; non-slot6? self modfiy code?
; Slot<<4 is in $2b by boot firmware? can we rely on that?
adrlo = $26 ; constant from boot prom
adrhi = $27 ; constant from boot prom
@ -154,6 +155,30 @@ md000x2_filename: ;.byte "MUSIC.D000X2 "
;unhook DOS and build nibble table
init:
; patch to use current drive
lda $2b ; has boot slot << 4 ?
ora #$80 ; add in $80
; c0e0
sta mlsmc06+1
; c0e8
clc
adc #8
sta mlsmc02+1
; c0e9
clc
adc #1
sta mlsmc01+1
; c0ec
clc
adc #3
sta mlsmc03+1
sta mlsmc04+1
sta mlsmc05+1
jsr $fe93 ; clear COUT
jsr $fe89 ; clear KEYIN
@ -192,7 +217,7 @@ L3: inx ; increment x x=4, a=0f
; turn on drive and read volume table of contents
opendir:
lda $c0e9 ; turn slot#6 drive on
mlsmc01:lda $c0e9 ; turn slot#6 drive on
ldx #0
stx adrlo ; zero out adrlo
stx secsize ; zero out secsize
@ -364,7 +389,7 @@ readdone:
sta adrhi
bcc readfirst
lda $c0e8
mlsmc02:lda $c0e8
; restore from stack bytes that were overwritten by extra read
@ -424,14 +449,14 @@ readdata:
bne re_read_addr
L12:
ldx $c0ec ; read until valid data (high bit set)
mlsmc03:ldx $c0ec ; read until valid data (high bit set)
bpl L12
eor nibtbl-$80, x
sta bit2tbl-$aa, y
iny
bne L12
L13:
ldx $c0ec ; read until valid data (high bit set)
mlsmc04:ldx $c0ec ; read until valid data (high bit set)
bpl L13
eor nibtbl-$80, x
sta (adrlo), y ; the real address
@ -496,7 +521,7 @@ L17:
tay ; we need Y=#$AA later
readnib:
lda $c0ec ; read until valid (high bit set)
mlsmc05:lda $c0ec ; read until valid (high bit set)
bpl readnib
seekret:
@ -553,7 +578,7 @@ L24:
rol
tax
lsr
lda $c0e0, x
mlsmc06:lda $c0e0, x
L25:
ldx #$12
L26:
@ -589,30 +614,32 @@ repeat_until_right_sector:
;
readdata:
mlsmc07:
ldy $c0ec ; read data until valid
bpl readdata
find_D5:
cpy #$d5 ; if not D5, repeat
bne readdata
find_AA:
mlsmc08:
ldy $c0ec ; read data until valid, should be AA
bpl find_AA
cpy #$aa ; we need Y=#$AA later
bne find_D5
find_AD:
lda $c0ec ; read data until high bit set (valid)
mlsmc09:lda $c0ec ; read data until high bit set (valid)
bpl find_AD
eor #$ad ; should match $ad
bne * ; lock if didn't find $ad (failure)
L12:
ldx $c0ec ; read data until high bit set (valid)
mlsmc0A:ldx $c0ec ; read data until high bit set (valid)
bpl L12
eor nibtbl-$80, x
sta bit2tbl-$aa, y
iny
bne L12
L13:
ldx $c0ec ; read data until high bit set (valid)
mlsmc0B:ldx $c0ec ; read data until high bit set (valid)
bpl L13
eor nibtbl-$80, x
sta (adrlo), y ; the real address
@ -643,20 +670,20 @@ L15:
;=================
; Find address field, put track in cutrk, sector in tmpsec
readadr:
lda $c0ec ; read data until we find a $D5
mlsmc0C:lda $c0ec ; read data until we find a $D5
bpl readadr
adr_d5:
cmp #$d5
bne readadr
adr_aa:
lda $c0ec ; read data until we find a $AA
mlsmc0D:lda $c0ec ; read data until we find a $AA
bpl adr_aa
cmp #$aa
bne adr_d5
adr_96:
lda $c0ec ; read data until we find a $96
mlsmc0E:lda $c0ec ; read data until we find a $96
bpl adr_96
cmp #$96
bne adr_d5
@ -669,12 +696,12 @@ adr_read_two_bytes:
sta curtrk ; store out current track
tax
L20:
lda $c0ec ; read until full value
mlsmc0F:lda $c0ec ; read until full value
bpl L20
rol
sta tmpsec
L21:
lda $c0ec ; read until full value
mlsmc10:lda $c0ec ; read until full value
bpl L21 ; sector value is (v1<<1)&v2????
and tmpsec
dey ; loop 3 times
@ -730,7 +757,7 @@ L118:
and #3
rol
tax
sta $c0e0, x
mlsmc11:sta $c0e0, x
L119:
ldx #$13
L120: