User Tools

Site Tools


base:decrease_x_register_by_more_than_1

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revisionPrevious revision
Last revisionBoth sides next revision
base:decrease_x_register_by_more_than_1 [2017-03-04 22:14] – [Decreasing the X register by more than 1] monte_carlosbase:decrease_x_register_by_more_than_1 [2017-03-29 08:01] – [Fill sprite with vertical pattern (containing $ff, $7f, $3f)] shrydar
Line 43: Line 43:
 ====== Examples ====== ====== Examples ======
  
-===== Fill sprite with vertical pattern (containing $ff, $7f, $3f) =====+===== Fill sprite with vertical pattern (containing $ff, $bf, $7f, $3f) =====
  
 <code> <code>
Line 52: Line 52:
 lda #yy lda #yy
 sta spr+o1,x sta spr+o1,x
-lda #$ff or $7f or $3f+lda #$ff or $bf or $7f or $3f
 sta spr+o2,x sta spr+o2,x
 axs#3 axs#3
Line 60: Line 60:
  
 where o0,o1,o2 is an excluding choice of {0,1,2}. where o0,o1,o2 is an excluding choice of {0,1,2}.
-On one column of the sprite a must contain $ff, $7f or $3f, because if it is anded with the value of the x reg, x must be contained. As x runs from 60 to 0 (where 63 is $3f) this is only the case for these three values.+On one column of the sprite a must contain $ff, $bf, $7f or $3f, because if it is anded with the value of the x reg, x must be preserved. As x runs from 60 to 0 (where 63 is $3f) this is only the case for these four values.
  
 ===== Info on SBX/AXS on external sites ===== ===== Info on SBX/AXS on external sites =====
   * [[http://unusedino.de/ec64/technical/aay/c64/bsbx.htm|Ninjas reference]]   * [[http://unusedino.de/ec64/technical/aay/c64/bsbx.htm|Ninjas reference]]
   * [[http://www.oxyron.de/html/opcodes02.html|Grahams reference]]   * [[http://www.oxyron.de/html/opcodes02.html|Grahams reference]]
base/decrease_x_register_by_more_than_1.txt · Last modified: 2017-03-30 12:44 by ftc