Routines
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9229: Screen Address One Pixel Below
Used by the routines at DrawBackground, 923A and Yin_Yang_Copy.
Input
HL Current position
Output
HL Address for new position
Calculates the new address for writing a sprite pixel, in a downward direction, taking into consideration the screen memory layout.
ScreenPos1PixelBelow 9229 INC H Increment H by one to move down one pixel on screen.
922A LD A,H Stash H in A temporarily.
922B AND %00000111 Keep only bits 0-2.
922D JR NZ,ScreenPos1PixelBelow_Return If a character line has not been crossed then jump to ScreenPos1PixelBelow_Return to return.
922F LD A,$20 L+=20.
9231 ADD A,L
9232 LD L,A
9233 JR C,ScreenPos1PixelBelow_Return If a new section of the screen has not been crossed, jump to ScreenPos1PixelBelow_Return to return.
9235 LD A,H H-=08.
9236 SUB $08
9238 LD H,A
ScreenPos1PixelBelow_Return 9239 RET Return.
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