mirror of
https://github.com/deater/dos33fsprogs.git
synced 2024-06-09 07:29:32 +00:00
53 lines
1.0 KiB
ArmAsm
53 lines
1.0 KiB
ArmAsm
;================================
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; plot_setup
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;================================
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plot_setup:
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lsr ; shift bottom bit into carry ; 2
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tay
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bcc do_plot_even ; 2nt/3
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do_plot_odd:
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lda #$f0 ; 2
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bcs do_plot_c_done ; 2nt/3
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do_plot_even:
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lda #$0f ; 2
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do_plot_c_done:
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sta mask_smc2+1 ;
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eor #$FF ; 2
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sta mask_invert_smc1+1 ;
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lda gr_offsets_l,Y ; lookup low-res memory address ; 4
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sta gbasl_smc1+1
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sta gbasl_smc2+1
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lda gr_offsets_h,Y ; 4
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clc
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adc DRAW_PAGE ; add in draw page offset ; 3
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sta gbasl_smc1+2
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sta gbasl_smc2+2
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;================================
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; plot1
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;================================
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plot1:
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mask_invert_smc1:
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lda #$ff ; load mask ; 2
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gbasl_smc1:
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and $400,Y ; mask to preserve on-screen color ; 4+
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sta COLOR_MASK ; save temporarily ; 3
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color_smc:
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lda #$FF ; load color ; 2
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mask_smc2:
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and #$FF ; mask so only hi/lo we want ; 2
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ora COLOR_MASK ; combine with on-screen color ; 3
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gbasl_smc2:
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sta $400,Y ; save back out ; 5
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