mirror of
https://github.com/deater/dos33fsprogs.git
synced 2024-12-28 09:30:41 +00:00
258 lines
2.8 KiB
ArmAsm
258 lines
2.8 KiB
ArmAsm
DRAW_PAGE = $E6
|
|
ZL = $06
|
|
ZH = $07
|
|
SEEDLO = $4E
|
|
SEEDHI = $4F
|
|
|
|
NUM1 = $F0
|
|
NUM1L = $F1
|
|
NUM2 = $F2
|
|
NUM2L = $F3
|
|
RESULT = $F4
|
|
RESULT2 = $F5
|
|
RESULT3 = $F6
|
|
RESULT4 = $F7
|
|
XL = $F8
|
|
XH = $F9
|
|
YL = $FA
|
|
YH = $FB
|
|
MINUS = $FC
|
|
Z = $FD
|
|
|
|
HGR2 = $F3D8
|
|
HPLOT0 = $F457 ; plot (Y,X), (A)
|
|
HGLIN = $F53A ; plot to (A,X), (Y)
|
|
HCLEAR0 = $F3F2 ; clear current hgr page to blackh
|
|
HCOLOR = $F6F0 ; color in X (must be 0..7)
|
|
|
|
|
|
lda #$ff
|
|
sta XH
|
|
|
|
ldx #0
|
|
|
|
jmp check_bounds
|
|
populate_loop:
|
|
; Z = XXYY YYYY
|
|
; C=Z*.125
|
|
; A=A+(A-64)*C
|
|
; B=B+(B-64)*C
|
|
|
|
|
|
|
|
; X is in NUM1 for this
|
|
|
|
lda #0
|
|
sta MINUS
|
|
|
|
sec
|
|
lda XH
|
|
sbc #64
|
|
bpl no_minus
|
|
set_minus:
|
|
inc MINUS
|
|
|
|
sec
|
|
lda #0
|
|
sbc XL
|
|
sta NUM1
|
|
lda #0
|
|
sbc XH
|
|
sta NUM1+1
|
|
jmp do_mult
|
|
|
|
no_minus:
|
|
sta NUM1+1
|
|
lda XL
|
|
sta NUM1
|
|
|
|
do_mult:
|
|
lda #0
|
|
sta NUM2+1
|
|
lda Z
|
|
sta NUM2
|
|
|
|
txa
|
|
pha
|
|
|
|
jsr mult16
|
|
|
|
pla
|
|
tax
|
|
|
|
; result has result but due to our fixed point
|
|
; we want to shift the whole thing left by 2
|
|
; then grab RESULT+2 as high and RESULT+1 as low
|
|
|
|
rol RESULT+1
|
|
rol RESULT+2
|
|
ror RESULT+1
|
|
lda RESULT+2
|
|
|
|
lda RESULT+1 ; low
|
|
sta NUM1
|
|
lda RESULT+2 ; hight
|
|
sta NUM1+1
|
|
|
|
; add to X; subtract if minus
|
|
lda MINUS
|
|
beq not_minus
|
|
|
|
sec
|
|
lda #00
|
|
sbc NUM1
|
|
sta NUM1
|
|
lda #00
|
|
sbc NUM1+1
|
|
sta NUM1+1
|
|
|
|
not_minus:
|
|
clc
|
|
lda XL
|
|
adc NUM1
|
|
sta XL
|
|
lda XH
|
|
adc NUM1+1
|
|
sta XH
|
|
|
|
; Z=Z+.125
|
|
|
|
clc
|
|
lda Z
|
|
adc #$8
|
|
sta Z
|
|
|
|
|
|
; check to see if out of bounds
|
|
check_bounds:
|
|
lda XH
|
|
bmi redo_point
|
|
lda YH
|
|
bpl all_good
|
|
|
|
redo_point:
|
|
; store a break in the lines
|
|
lda #0
|
|
sta $1000,X
|
|
sta $1100,X
|
|
sta Z ; needed?
|
|
inx
|
|
|
|
jsr rand16
|
|
sta XH
|
|
jsr rand16
|
|
sta YH
|
|
|
|
all_good:
|
|
|
|
|
|
; write out
|
|
|
|
lda XH
|
|
sta $1000,X
|
|
lda YH
|
|
sta $1100,X
|
|
|
|
inx
|
|
beq done_pop
|
|
jmp populate_loop
|
|
done_pop:
|
|
;=========================
|
|
;=========================
|
|
;=========================
|
|
|
|
jsr HGR2
|
|
ldx #3
|
|
jsr HCOLOR
|
|
|
|
ldx #0
|
|
star_loop:
|
|
txa
|
|
and #$1
|
|
beq page2
|
|
page1: ; draw page1, show page2
|
|
bit $C055
|
|
lda #$20
|
|
bne adjust_page
|
|
page2:
|
|
bit $C054
|
|
lda #$40
|
|
adjust_page:
|
|
sta DRAW_PAGE
|
|
|
|
; clear background
|
|
jsr HCLEAR0
|
|
|
|
txa
|
|
pha
|
|
|
|
lda $1100,X ; ycoord
|
|
beq skip_draw
|
|
pha
|
|
ldy $1000,X ; xcoord
|
|
tya
|
|
tax
|
|
ldy #0
|
|
pla
|
|
|
|
jsr HPLOT0 ; plot (Y,X), (A)
|
|
|
|
skip_draw:
|
|
|
|
pla
|
|
tax
|
|
|
|
inx
|
|
jmp star_loop
|
|
|
|
|
|
; make sure seed isn't 0000
|
|
rand16:
|
|
; batari rand16
|
|
lda SEEDHI
|
|
lsr
|
|
rol SEEDLO
|
|
bcc noeor
|
|
eor #$B4
|
|
noeor:
|
|
sta SEEDHI
|
|
eor SEEDLO
|
|
|
|
; we only want 127 bits
|
|
and #$7f
|
|
|
|
rts
|
|
|
|
|
|
;=====================
|
|
;=====================
|
|
; 16x16 -> 32 multiply
|
|
;=====================
|
|
;=====================
|
|
; destroys NUM2
|
|
mult16:
|
|
lda #0 ; Initialize RESULT to 0
|
|
sta RESULT+2
|
|
ldx #16 ; There are 16 bits in NUM2
|
|
L1:
|
|
lsr NUM2+1 ; top part of 16 bit shift right
|
|
ror NUM2
|
|
bcc L2 ; 0 or 1?
|
|
tay ; If 1, add NUM1 (hi byte of RESULT is in A)
|
|
clc
|
|
lda NUM1
|
|
adc RESULT+2
|
|
sta RESULT+2
|
|
tya
|
|
adc NUM1+1
|
|
L2:
|
|
ror ; "Stairstep" shift
|
|
ror RESULT+2
|
|
ror RESULT+1
|
|
ror RESULT
|
|
dex
|
|
bne L1
|
|
sta RESULT+3
|
|
|
|
rts
|