Routines
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E909: Convert a screen address to an attribute address
Used by the routines at CD5C, D567, D895, D951 and E663.
Input
DE On entry, holds the screen address. On return, holds the attribute address
E909 CALL $E8D2 Round the screen address to the nearest whole cell.
This entry point is used by the routine at D1CE.
E90C LD A,D Divide the high byte by 8 to give an offset of 08, 09 or 0A.
E90D RRCA
E90E RRCA
E90F RRCA
E910 AND $03 Keep only the bottom 3 bits, to give an offset of 0, 1 or 2.
E912 OR $58 Add the base address of the attribute buffer, to give 58 59 or 5A.
E914 LD D,A Store this as the new high byte. The low byte is unchanged.
E915 RET Return.
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