165 lines
2.4 KiB
ArmAsm
165 lines
2.4 KiB
ArmAsm
|
|
CH = $24
|
|
CV = $25
|
|
BASL = $28
|
|
BASH = $29
|
|
SEEDL = $4E
|
|
FACL = $9D
|
|
FACH = $9E
|
|
|
|
DRAW_PAGE = $FF
|
|
|
|
PAGE0 = $C054
|
|
GETCHAR = $D72C
|
|
HGR = $F3E2
|
|
SETTXT = $FB39
|
|
TABV = $FB5B ; store A in CV and call MON_VTAB
|
|
STORADV = $FBF0 ; store A at (BASL),CH, advancing CH, trash Y
|
|
MON_VTAB = $FC22 ; VTAB to CV
|
|
VTABZ = $FC24 ; VTAB to value in A
|
|
HOME = $FC58
|
|
WAIT = $FCA8 ;; delay 1/2(26+27A+5A^2) us
|
|
|
|
COUT = $FDED
|
|
COUT1 = $FDF0
|
|
COUTZ = $FDF6 ; cout but ignore inverse flag
|
|
|
|
ypos = $2000
|
|
xpos = $2100
|
|
textl = $2200
|
|
texth = $2300
|
|
|
|
move:
|
|
jsr HGR
|
|
|
|
sta DRAW_PAGE
|
|
|
|
jsr SETTXT
|
|
|
|
|
|
next_frame:
|
|
ldx #0
|
|
next_text:
|
|
lda xpos,X
|
|
bne not_new
|
|
|
|
new_text:
|
|
jsr random8
|
|
and #$1f
|
|
adc #$4
|
|
sta xpos,X
|
|
|
|
jsr random8
|
|
and #$f
|
|
sta ypos,X
|
|
|
|
lda #<text
|
|
sta textl,X
|
|
lda #>text
|
|
sta texth,X
|
|
|
|
not_new:
|
|
lda xpos,X
|
|
sta CH
|
|
lda ypos,X
|
|
sta CV
|
|
|
|
jsr MON_VTAB
|
|
|
|
lda BASH
|
|
clc
|
|
adc DRAW_PAGE
|
|
sta BASH
|
|
|
|
|
|
ldy #0
|
|
lda textl,X
|
|
sta FACL
|
|
lda texth,X
|
|
sta FACH
|
|
|
|
txa
|
|
pha
|
|
|
|
print_loop:
|
|
jsr GETCHAR
|
|
|
|
php
|
|
|
|
ora #$80
|
|
jsr STORADV
|
|
|
|
plp
|
|
|
|
bpl print_loop
|
|
|
|
big_done:
|
|
|
|
pla
|
|
tax
|
|
|
|
dec xpos,X
|
|
|
|
inx
|
|
cpx #20
|
|
bne next_text
|
|
|
|
flip_pages:
|
|
ldx #0
|
|
|
|
lda DRAW_PAGE
|
|
beq done_page
|
|
inx
|
|
done_page:
|
|
ldy PAGE0,X ; set display page to PAGE1 or PAGE2
|
|
|
|
eor #$4 ; flip draw page between $400/$800
|
|
sta DRAW_PAGE
|
|
|
|
clc
|
|
adc #$4
|
|
sta BASH
|
|
lda #$0
|
|
sta BASL
|
|
|
|
clear_screen_outer:
|
|
ldy #$f8
|
|
clear_screen_inner:
|
|
lda #$A0 ; space char
|
|
sta (BASL),Y ; 100 101 110 111
|
|
dey
|
|
cpy #$FF
|
|
bne clear_screen_inner
|
|
inc BASH
|
|
lda BASH
|
|
and #$3
|
|
bne clear_screen_outer
|
|
|
|
lda #$50
|
|
jsr WAIT
|
|
|
|
jmp next_frame
|
|
|
|
|
|
;=============================
|
|
; random8
|
|
;=============================
|
|
; 8-bit 6502 Random Number Generator
|
|
; Linear feedback shift register PRNG by White Flame
|
|
; http://codebase64.org/doku.php?id=base:small_fast_8-bit_prng
|
|
|
|
random8:
|
|
lda SEEDL ; 2
|
|
beq doEor ; 2
|
|
asl ; 1
|
|
beq noEor ; if the input was $80, skip the EOR ; 2
|
|
bcc noEor ; 2
|
|
doEor: eor #$1d ; 2
|
|
noEor: sta SEEDL ; 2
|
|
rts
|
|
|
|
|
|
text:
|
|
.byte "HELL",'O'|$80
|
|
|