mirror of
https://github.com/deater/dos33fsprogs.git
synced 2024-12-29 00:31:52 +00:00
158 lines
3.0 KiB
ArmAsm
158 lines
3.0 KiB
ArmAsm
; Autumn, based on the code in Hellmood's Autumn
|
|
; by deater (Vince Weaver) <vince@deater.net>
|
|
|
|
; Zero Page Addresses
|
|
|
|
XCOORDL = $F6
|
|
XCOORDH = $F7
|
|
YCOORDL = $F8
|
|
YCOORDH = $F9 ; shapetable ROT
|
|
EBP1 = $FA
|
|
EBP2 = $FB
|
|
EBP3 = $FC
|
|
EBP4 = $FD
|
|
COLORL = $FE
|
|
COLORH = $FF
|
|
|
|
; Soft Switches
|
|
KEYPRESS= $C000
|
|
KEYRESET= $C010
|
|
|
|
; ROM routines
|
|
; Some of these are in the Applesoft ROMs so need at least an Apple II+
|
|
; or later to run
|
|
|
|
TEXT = $FB36 ; Set text mode
|
|
HGR2 = $F3D8 ; Set full-screen hi-res mode using page 2 ($4000)
|
|
; 280x192 6-colors
|
|
HPLOT0 = $F457 ; Plot point, (Y,X) = Horizontal, (A=Vertical)
|
|
HCOLOR = $F6EC ; Set color in X, must be 0..7
|
|
|
|
|
|
autumn:
|
|
|
|
;===================
|
|
; init screen ; Instruction Length
|
|
jsr HGR2 ; 3
|
|
|
|
autumn_forever:
|
|
|
|
; save old Xcoord value to X/Y for later
|
|
; push/pop is 1 byte each but have to get
|
|
; value into accumulator first
|
|
ldx XCOORDL ; 2
|
|
ldy XCOORDH ; 2
|
|
|
|
; 16-bit subtraction x=x-y
|
|
; need to set carry before subtraction on 6502
|
|
txa ; 1
|
|
sec ; 1
|
|
sbc YCOORDL ; 2
|
|
sta XCOORDL ; 2
|
|
tya ; 1
|
|
sbc YCOORDH ; 2
|
|
|
|
; 16-bit arithmatic shift right of X
|
|
; 6502 has no asr instruction
|
|
; cmp #$80 sets carry if high bit set
|
|
cmp #$80 ; 2 ; XCOORDH still in A from before
|
|
ror ; 1
|
|
sta XCOORDH ; 2
|
|
ror XCOORDL ; 2
|
|
|
|
; 16-bit add, ycoord=ycoord+oldx
|
|
clc ; 1
|
|
txa ; 1
|
|
adc YCOORDL ; 2
|
|
sta YCOORDL ; 2
|
|
tya ; 1
|
|
adc YCOORDH ; 2
|
|
|
|
; 16-bit arithmatic shift right of y-coord
|
|
cmp #$80 ; 2 ; YCOORDH still in A from before
|
|
ror ; 1
|
|
sta YCOORDH ; 2
|
|
ror YCOORDL ; 2
|
|
|
|
; 32 bit rotate of low bit shifted out of Y-coordinate
|
|
ror EBP1 ; 2
|
|
ror EBP2 ; 2
|
|
ror EBP3 ; 2
|
|
ror EBP4 ; 2
|
|
|
|
; branch if carry set
|
|
bcs label_11f ; 2
|
|
|
|
; 16-bit increment of color
|
|
inc COLORL ; 2
|
|
bne no_oflo ; 2
|
|
inc COLORH ; 2
|
|
no_oflo:
|
|
|
|
; 16-bit add of X-coord by 0x80
|
|
; this keeps the drawing roughly to the 280x192 screen
|
|
; carry should still be clear (inc doesn't set it)
|
|
lda XCOORDL ; 2
|
|
adc #$80 ; 2
|
|
sta XCOORDL ; 2
|
|
bcc no_oflo2 ; 2
|
|
inc XCOORDH ; 2
|
|
no_oflo2:
|
|
|
|
; 16-bit negate of Y-coord
|
|
sec ; 1
|
|
lda #0 ; 2
|
|
sbc YCOORDL ; 2
|
|
sta YCOORDL ; 2
|
|
lda #0 ; 2
|
|
sbc YCOORDH ; 2
|
|
sta YCOORDH ; 2
|
|
|
|
label_11f:
|
|
|
|
; skipping the color manipulation done here by original
|
|
|
|
; mix colors a bit?
|
|
|
|
; 16-bit shift of color
|
|
; 2nd is a rotate as asl doesn't shift in cary
|
|
|
|
lda COLORL ; 2
|
|
asl ; 1 ; shl %ax
|
|
rol COLORH ; 2
|
|
eor COLORH ; 2
|
|
sta COLORL ; 2
|
|
|
|
; get color mapping
|
|
; using a color lookup table looks best but too many bytes
|
|
; you can approximate something close to the lookup with
|
|
; two extra instructions
|
|
|
|
and #$7 ; 2
|
|
ora #$2 ; 2
|
|
tax ; 1
|
|
|
|
; if ycoord negative, loop
|
|
lda YCOORDH ; 2
|
|
bmi autumn_forever ; 2
|
|
|
|
; if top bits of xcoord, loop
|
|
lda XCOORDH ; 2
|
|
and #$f0 ; 2
|
|
bne autumn_forever ; 2
|
|
|
|
put_pixel:
|
|
|
|
; actually set the color
|
|
jsr HCOLOR ; 3
|
|
|
|
; set up paramaters for HPLOT call
|
|
ldx XCOORDL ; 2
|
|
ldy XCOORDH ; 2
|
|
lda YCOORDL ; 2
|
|
jsr HPLOT0 ; 3
|
|
|
|
jmp autumn_forever ; 3 ; if we get under 128 bytes
|
|
|
|
|