dos33fsprogs/demos/second/part04_chess_shapes/hgr_partial.s
Vince Weaver d4cedf0e7a second: chessboard falling
a hack but maybe good enough for now
2023-11-03 17:00:18 -04:00

47 lines
626 B
ArmAsm

; copy partial part of screen from $6000 to DRAW_PAGE
; HGR_X1,HGR_Y1 to HGR_X2,HGR_Y2 source
; destination = Y at HGR_DEST
hgr_partial:
lda HGR_DEST
sta dest_y_smc+1
ldx HGR_Y1 ; Y1
hgr_partial_outer_loop:
lda hposn_low,X
sta INL
lda hposn_high,X
ora #$40 ; convert to $6000
sta INH
txa
pha
dest_y_smc:
ldx #100 ; DEST_Y
lda hposn_low,X
sta OUTL
lda hposn_high,X
clc
adc DRAW_PAGE
sta OUTH
pla
tax
ldy HGR_X1 ; X1
hgr_partial_inner_loop:
lda (INL),Y
sta (OUTL),Y
iny
cpy HGR_X2 ; X2
bne hgr_partial_inner_loop
inc dest_y_smc+1
inx
cpx HGR_Y2 ; Y2
bne hgr_partial_outer_loop
rts