206 lines
3.1 KiB
ArmAsm
206 lines
3.1 KiB
ArmAsm
;=====================================================================
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;= ROUTINES
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;=====================================================================
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clear_screens:
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;===================================
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; Clear top/bottom of page 0
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;===================================
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lda #$0
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sta DRAW_PAGE
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jsr clear_top
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jsr clear_bottom
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;===================================
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; Clear top/bottom of page 1
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;===================================
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lda #$4
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sta DRAW_PAGE
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jsr clear_top
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jsr clear_bottom
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rts
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;================================
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; hlin_setup
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;================================
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; put address in GBASL/GBASH
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; Ycoord in A, Xcoord in Y
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hlin_setup:
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sty TEMPY ; 3
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tay ; y=A ; 2
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lda gr_offsets,Y ; lookup low-res memory address ; 4
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clc ; 2
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adc TEMPY ; 3
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sta GBASL ; 3
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iny ; 2
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lda gr_offsets,Y ; 4
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adc DRAW_PAGE ; add in draw page offset ; 3
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sta GBASH ; 3
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rts ; 6
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;===========
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; 35
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;================================
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; hlin_double:
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;================================
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; HLIN Y, V2 AT A
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; Y, X, A trashed
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; start at Y, draw up to and including X
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hlin_double:
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;int hlin_double(int page, int x1, int x2, int at) {
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jsr hlin_setup ; 41
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sec ; 2
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lda V2 ; 3
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sbc TEMPY ; 3
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tax ; 2
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inx ; 2
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;===========
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; 53
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; fallthrough
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;=================================
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; hlin_double_continue: width
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;=================================
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; width in X
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hlin_double_continue:
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ldy #0 ; 2
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lda COLOR ; 3
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hlin_double_loop:
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sta (GBASL),Y ; 6
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inc GBASL ; 5
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dex ; 2
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bne hlin_double_loop ; 2nt/3
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rts ; 6
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;=============
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; 53+5+X*16+5
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;================================
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; hlin_single:
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;================================
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; HLIN Y, V2 AT A
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; Y, X, A trashed
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hlin_single:
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jsr hlin_setup
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sec
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lda V2
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sbc TEMPY
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tax
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; fallthrough
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;=================================
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; hlin_single_continue: width
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;=================================
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; width in X
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hlin_single_continue:
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hlin_single_top:
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lda COLOR
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and #$f0
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sta COLOR
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hlin_single_top_loop:
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ldy #0
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lda (GBASL),Y
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and #$0f
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ora COLOR
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sta (GBASL),Y
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inc GBASL
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dex
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bne hlin_single_top_loop
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rts
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hlin_single_bottom:
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lda COLOR
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and #$0f
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sta COLOR
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hlin_single_bottom_loop:
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ldy #0
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lda (GBASL),Y
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and #$f0
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sta (GBASL),Y
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inc GBASL
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dex
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bne hlin_single_bottom_loop
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rts
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;=============================
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; clear_top
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;=============================
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clear_top:
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lda #$00
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;=============================
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; clear_top_a
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;=============================
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clear_top_a:
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sta COLOR
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; VLIN Y, V2 AT A
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lda #40
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sta V2
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lda #0
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clear_top_loop:
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ldy #0
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pha
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jsr hlin_double
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pla
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clc
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adc #$2
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cmp #40
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bne clear_top_loop
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rts
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clear_bottom:
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lda #$a0 ; NORMAL space
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sta COLOR
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lda #40
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sta V2
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clear_bottom_loop:
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ldy #0
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pha
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jsr hlin_double
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pla
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clc
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adc #$2
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cmp #48
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bne clear_bottom_loop
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rts
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; move these to zero page for slight speed increase?
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gr_offsets:
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.word $400,$480,$500,$580,$600,$680,$700,$780
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.word $428,$4a8,$528,$5a8,$628,$6a8,$728,$7a8
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.word $450,$4d0,$550,$5d0,$650,$6d0,$750,$7d0
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