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