mem: first fast_plot implementation

This commit is contained in:
Vince Weaver 2020-05-13 14:53:51 -04:00
parent 98b40afda7
commit 5b75e5cd02

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; fast plot
; roughly $4D (77) cycles
; note: ROM plot routine takes $5D (93) cycles
; color in COLOR
; horiz=y, vert=A (A trashed, XY Saved)
fast_plot:
stx TEMPX ; 3
ror ; get low bit in carry ; 2
php ; store for later ; 3
asl ; 2
tax ; 2
lda gr_offsets,X ; 4+
sta plot_smc+1 ; 4
sta load_old_smc+1 ; 4
lda gr_offsets+1,X ; 4+
sta plot_smc+2 ; 4
sta load_old_smc+2 ; 4
;===
; 36
;4->3,4->3,4->0,4->0, 4->5, 5->6
load_old_smc:
lda $400,Y ; 4+
plp ; 4
bcs plot_bottom ; 2/3t
;=====
; 11
plot_top:
and #$f0 ; 2
sta TEMP ; 3
lda COLOR ; 3
and #$0f ; 2
ora TEMP ; 3
jmp plot_smc ; 3
;====
; 16
plot_bottom:
and #$0f ; 2
sta TEMP ; 3
lda COLOR ; 3
and #$f0 ; 2
ora TEMP ; 3
plot_smc:
sta $400,Y ; 5
ldx TEMPX ; 3
rts ; 6
;====
; 14
;.align $100
gr_offsets:
.word $400,$480,$500,$580,$600,$680,$700,$780
.word $428,$4a8,$528,$5a8,$628,$6a8,$728,$7a8
.word $450,$4d0,$550,$5d0,$650,$6d0,$750,$7d0
gr_offsets_end:
;.assert >gr_offsets = >gr_offsets_end, error, "gr_offsets crosses page"