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executable file 372 lines (285 sloc) 4.471 kb
lst off
org $c00
*-------------------------------------------------
dum 0
curpage ds 1
xsave ds 1
ysave ds 1
asave ds 1
temp ds 1
tmplo ds 1
tmphi ds 1
level ds 1
isGS? ds 1
dend
framebase = $1000
*------------------------------------------------- show
*
* put on the show!
*
show bit $C010
lda #0
sta isGS?
bit $C081
sec
jsr $fe1f ;GS?
bcs :notGS
inc isGS?
* Use special show frame routine for //GS that
* writes directly to bank $E0, since page two
* text is not properly shadowed to that bank.
ldx #$4C ;jmp
ldy #GSshowframe
lda #>GSshowframe
stx showframe
sty showframe+1
sta showframe+2
* Make our lookup tables up in ramcard area
:notGS bit $C083
bit $C083
jsr MAKEfade_tbls
jsr lgr
:again
ldx #0
:fadein stx level
lda #0
jsr showframe
ldx level
inx
cpx #15
bcc :fadein
* Here we go...
lda #0
:floop pha
ldx #15
jsr showframe
pla
clc
adc #1
cmp #23
bcc :floop
ldx #15
:fadeout stx level
lda #22
jsr showframe
ldx level
dex
bpl :fadeout
bit $C000
bpl *-3
bit $C010
jmp :again
*------------------------------------------------- lgr
*
* Clear and display lo-resolution screen
*
lgr sta $C000 ;turn off 55.54 select
sta $C00C ;40 columns
bit $C052 ;full screen
bit $C055 ;show page two
bit $C056 ;lores
bit $C050 ;graphics on
lda #4 ;use page one next
sta curpage
ldy #0
sty tmplo
sta tmphi
tya
ldx #8
:0 sta (tmplo),y
iny
bne :0
inc tmphi
dex
bne :0
rts
*------------------------------------------------- loget
*
* Enter with a:frame number
* x:fade level
*
showframe asl
asl
adc #>framebase
sta :src+2 ;hi byte
txa
ora #>fade_table
sta :fademod+2
lda curpage
sta :dst+2
eor #4!8
sta curpage
lda #4
sta temp
ldx #0
:loop
:src ldy $1100,x
:fademod lda fade_table+$F00,y
:dst sta $0400,x
inx
bne :loop
inc :src+2 ;hibyte
inc :dst+2 ; " "
dec temp
bne :loop
]waitvbl jsr waitvbl
bit $C055
lda curpage
cmp #4
beq *+5
bit $C054
rts
GSshowframe asl
asl
adc #>framebase
sta :src+2 ;hi byte
txa
ora #>fade_table
sta :fademod+2
lda curpage
sta :dst+2
eor #4!8
sta curpage
lda #4
sta temp
ldx #0
:loop
:src ldy $1100,x
:fademod lda fade_table+$F00,y
:dst stal $E00400,x
inx
bne :loop
inc :src+2 ;hibyte
inc :dst+2 ; " "
dec temp
bne :loop
beq ]waitvbl
*------------------------------------------------- waitvbl
*
* Wait for a few vbl's to go by!
*
waitvbl ldx #6
:0 bit $C019
bpl :0
:1 bit $C019
bmi :1
dex
bne :0
rts
*------------------------------------------------- MAKEfade_tbls
*
* Make 16 lookup tables each containing 256 bytes
* for the 16 levels of fade-in.
*
MAKEfade_tbls dum 0
:curtmp ds 2 ;ptr into current tmp_scale table
:curfade ds 2 ;ptr into current page of fade table
:temp ds 1
:ysave ds 1
dend
jsr MAKEtmp_scale
ldy #tmp_scale
lda #>tmp_scale
sty :curtmp
sta :curtmp+1
ldy #fade_table
lda #>fade_table
sty :curfade
sta :curfade+1
* byte loop
ldy #0
:bloop tya
and #$0F
jsr :convert
sta :temp
tya
lsr
lsr
lsr
lsr
jsr :convert
asl
asl
asl
asl
ora :temp
sta (:curfade),y
iny
bne :bloop
* next fade table
inc :curfade+1
* next tmp table
clc
lda :curtmp
adc #16
sta :curtmp
bcc :bloop
rts
* given a=0-15, in lores unsequential grey scale,
* convert it back to sequential, lookup new value
* in tmp_scale table and then convert back to
* lores unsequential.
:convert sty :ysave
* Convert lores color back to sequential 00-0F
tax
lda :unlores,x
* Scale it
tay
lda (:curtmp),y
* Convert back to unsequential lores color
tax
lda isGS?
beq :notGS
lda :loresGS,x
bra :isGS
:notGS lda :lores2e,x
:isGS ldy :ysave
rts
:unlores hex 000301070405020a
hex 06080b0c090e0d0f
:loresGS hex 0002060104050803
hex 090c070a0b0e0d0f
:lores2e hex 00000000
hex 02020202
hex 06060606
hex 07070707
*------------------------------------------------- MAKEtmp_scale
*
* Make lookup table that contains values
* for 0-15 multiplied by 1/16... 16/16.
*
MAKEtmp_scale dum 0
:color ds 1
:scale ds 1
dend
lda #1 ;start with 1/16th
sta :scale
:sloop ldy #0
:cloop sty :color
lda #0
ldx :scale
:mloop clc
adc :color
dex
bne :mloop
lsr
lsr
lsr
lsr
:smc sta tmp_scale,y
iny
cpy #16
bne :cloop
inc :scale
lda :smc+1
clc
adc #16
sta :smc+1
bcc :sloop
rts
*-------------------------------------------------
dum $D000
fade_table ds $1000
tmp_scale ds $100
dend
*------------------------------------------------- EOF
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