2021-02-20 18:00:34 -05:00
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( screen )
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:dev/r fff8 ( std read port )
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:dev/w fff9 ( std write port )
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;centerx 2 ;centery 2 ;i 2
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|0100 @RESET
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( set read/write to dev/screen )
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#01 DUP =dev/r =dev/w
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( find screen center )
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#00 IOR2 #0002 DIV2 =centerx
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#02 IOR2 #0002 DIV2 =centery
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( draw hor line )
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#0000 =i
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@draw-hor
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#03 ~i ~centery ,draw-pixel JSR
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~i #0002 ADD2 =i ( increment )
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~i #00 IOR2 LTH2 ,draw-hor ROT JMP? POP2
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( draw ver line )
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#0000 =i
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@draw-ver
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#03 ~centerx ~i ,draw-pixel JSR
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~i #0002 ADD2 =i ( increment )
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~i #02 IOR2 LTH2 ,draw-ver ROT JMP? POP2
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( draw pixel in the middle )
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#01 ~centerx ~centery ,draw-pixel JSR
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BRK
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@draw-pixel
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IOW2 ( y short )
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IOW2 ( x short )
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IOW ( color byte )
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RTS
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|c000 @FRAME BRK
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|d000 @ERROR BRK
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|FFF0 [ f0ac f0bb f053 ] ( palette )
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2021-02-20 20:14:36 -05:00
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|FFFA .RESET .FRAME .ERROR ( vectors )
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