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base:decrease_x_register_by_more_than_1

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base:decrease_x_register_by_more_than_1 [2017-03-29 08:01]
shrydar [Fill sprite with vertical pattern (containing $ff, $7f, $3f)]
base:decrease_x_register_by_more_than_1 [2017-03-30 12:44] (current)
ftc
Line 12: Line 12:
 </code> </code>
  
-This procedure takes 8 cycles (and 5 bytes in mem). If the value of the carry flag is always known at this point in the code, it can be removed and the snippet would then take 6 cycles (and 4 bytes in mem). However, there is another way to do it. You can use the illegal opcode SBX (sometimes called AXS). It operates like this:+This procedure takes 8 cycles (and 5 bytes in mem). If the value of the carry flag is always known at this point in the code, the SEC instruction can be removed and the snippet would then take 6 cycles (and 4 bytes). However, there is another way to do it. You can use the illegal opcode SBX (sometimes called AXS). It operates like this:
  
   - AND X with A and put result in X   - AND X with A and put result in X
base/decrease_x_register_by_more_than_1.txt ยท Last modified: 2017-03-30 12:44 by ftc