67 lines
1.1 KiB
NASM
67 lines
1.1 KiB
NASM
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;Cycle through color values
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.dseg
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colorval: .alloc 1
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xpos: .alloc 1
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ypos: .alloc 1
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temp: .alloc 1
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.def screen_base 0xC000
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.cseg
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;start at x=0 y=0 color = 0
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iloada 0
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copya
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store xpos
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store ypos
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store colorval
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loop_x:
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;shift y 7 spaces to make x, y address
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loada ypos
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iloadb 7
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lshift
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store temp
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loada temp
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loadb xpos
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add ;R now has ypos*128 + xpos
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store temp
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loada temp
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iloadb screen_base
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add ;R is now screen pixel address
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setp ;pixel address now in register P
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loada colorval
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storep ;puts colorval into addresss pointed to by P
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;increment color
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loada colorval
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iloadb 1
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add
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store colorval
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;increment x, check if 128
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loada xpos
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iloadb 1
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add
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store xpos
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loada xpos
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iloadb 128
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sub
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jumpnz loop_x ;X wasnt at 128
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;X went to 128, reset and increment Y
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iloada 0
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copya
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store xpos
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loada ypos
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iloadb 1
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add
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store ypos
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;check if ypos went to 128 and reset if it did
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loada ypos
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iloadb 128
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sub
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jumpnz loop_x
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;need to reset Y
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iloada 0
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copya
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store ypos
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jump loop_x
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