dos33fsprogs/demosplash/gr_fast_clear.s
Vince Weaver 46b20a427c ds: fix long running mystery of gr_clear
cycle counting was wrong in gr_clear

update appleii_intro to compensate

move some stuff around
2019-11-15 12:31:28 -05:00

56 lines
1.0 KiB
ArmAsm

;=========================================================
; clear_all
;=========================================================
; clear 48 rows
; page in DRAW_PAGE
; 45+4+(45*120)+5 = 5454
gr_clear_all:
clc ; 2
lda DRAW_PAGE ; 3
adc #4 ; 2
sta __caf+2 ; 4
sta __caf+5 ; 4
adc #1 ; 2
sta __caf+8 ; 4
sta __caf+11 ; 4
adc #1 ; 2
sta __caf2+2 ; 4
sta __caf2+5 ; 4
adc #1 ; 2
sta __caf2+8 ; 4
sta __caf2+11 ; 4
;===========
; 45
ldy #119 ; 2
clear_all_color:
lda #$00 ; 2
;============
; 4
clear_all_fast_loop:
__caf:
sta $400,Y ; 5
sta $480,Y ; 5
sta $500,Y ; 5
sta $580,Y ; 5
__caf2:
sta $600,Y ; 5
sta $680,Y ; 5
sta $700,Y ; 5
sta $780,Y ; 5
dey ; 2
bpl clear_all_fast_loop ; 3
;============
; 45
; -1
rts ; 6
gr_clear_all_end:
.assert >gr_clear_all = >gr_clear_all_end, error, "gr_clear_all crosses page"