mirror of
https://github.com/deater/dos33fsprogs.git
synced 2024-11-10 14:05:59 +00:00
48 lines
899 B
ArmAsm
48 lines
899 B
ArmAsm
|
;================================
|
||
|
|
; plot routine
|
||
|
|
;================================
|
||
|
|
; Xcoord in XPOS
|
||
|
|
; Ycoord in YPOS
|
||
|
|
; color in COLOR
|
||
|
|
plot:
|
||
|
|
lda YPOS ; 3
|
||
|
|
|
||
|
|
lsr ; shift bottom bit into carry ; 2
|
||
|
|
|
||
|
|
bcc plot_even ; 2nt/3
|
||
|
|
plot_odd:
|
||
|
|
ldx #$f0 ; 2
|
||
|
|
bcs plot_c_done ; 2nt/3
|
||
|
|
plot_even:
|
||
|
|
ldx #$0f ; 2
|
||
|
|
plot_c_done:
|
||
|
|
stx MASK ; 3
|
||
|
|
|
||
|
|
asl ; shift back (now even) ; 2
|
||
|
|
tay ; 2
|
||
|
|
|
||
|
|
lda gr_offsets,Y ; lookup low-res memory address ; 4
|
||
|
|
clc ; 2
|
||
|
|
adc XPOS ; 3
|
||
|
|
sta GBASL ; 3
|
||
|
|
|
||
|
|
lda gr_offsets+1,Y ; 4
|
||
|
|
adc DRAW_PAGE ; add in draw page offset ; 3
|
||
|
|
sta GBASH ; 3
|
||
|
|
|
||
|
|
ldy #0 ; 2
|
||
|
|
|
||
|
|
plot_write:
|
||
|
|
lda MASK ; 3
|
||
|
|
eor #$ff ; 2
|
||
|
|
|
||
|
|
and (GBASL),Y ; 5+
|
||
|
|
sta COLOR_MASK ; 3
|
||
|
|
|
||
|
|
lda COLOR ; 3
|
||
|
|
and MASK ; 3
|
||
|
|
ora COLOR_MASK ; 3
|
||
|
|
sta (GBASL),Y ; 6
|
||
|
|
|
||
|
|
rts ; 6
|