dos33fsprogs/demos/mode7_demo/gr_copy.s
Vince Weaver b1238af49d re-arranged the entire directory structure
this will probably upset people
2021-01-05 15:29:31 -05:00

54 lines
1.4 KiB
ArmAsm

;=========================================================
; gr_copy_to_current
;=========================================================
; copy 0xc00 to DRAW_PAGE
; ORIGINAL: 2 + 8*38 + 4*80*23 + 4*120*26 + 13 = 20,159 = 20ms = 50Hz
;
; OPTIMIZED: 2+ 8*38 + 9*4 + 7*4 + 14*120*4 + 14*80*4 + 9*8 + 6 =
; 11,648 = 11ms = 90Hz
gr_copy_to_current:
ldx #0 ; set ypos to zero ; 2
gr_copy_loop:
lda gr_offsets,X ; lookup low byte for line addr ; 4+
sta gr_copy_line+1 ; out and in are the same ; 4
sta gr_copy_line+4 ; 4
lda gr_offsets+1,X ; lookup high byte for line addr ; 4+
clc ; 2
adc DRAW_PAGE ; 3
sta gr_copy_line+5 ; 4
lda gr_offsets+1,X ; lookup high byte for line addr ; 4+
adc #$8 ; for now, fixed 0xc ; 2
sta gr_copy_line+2 ; 4
ldy #0 ; set xpos counter to 0 ; 2
cpx #$8 ; don't want to copy bottom 4*40 ; 2
bcs gr_copy_above4 ; 2nt/3
gr_copy_below4:
ldy #119 ; for early ones, copy 120 bytes ; 2
bcc gr_copy_line ; ; 3
gr_copy_above4: ; for last four, just copy 80 bytes
ldy #79 ; 2
gr_copy_line:
lda $ffff,Y ; load a byte (self modified) ; 4+
sta $ffff,Y ; store a byte (self modified) ; 5
dey ; decrement pointer ; 2
bpl gr_copy_line ; ; 2nt/3
gr_copy_line_done:
inx ; increment ypos value ; 2
inx ; twice, as address is 2 bytes ; 2
cpx #16 ; there are 8*2 of them ; 2
bne gr_copy_loop ; if not, loop ; 3
rts ; 6