Routines
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DACD: Calculate Screen Block Address
Used by the routines at D609, D8CA, D939, D989, D9F0, DA56, DAE7, Print_HelperPreviewImage, DC74, Draw_Cursor, E81F, E83A and StaticAnimation.
Input
B X co-ordinate
C Y co-ordinate
Output
HL Screen buffer address pointer
Calculate_ScreenBlockAddress DACD LD A,B Load the X position into A.
DACE AND %11111000 Divide X by 08 to extract only the column number.
DAD0 ADD A,$40 Add 40 to get the high byte of screen address and store the result in H.
DAD2 LD H,A
DAD3 LD A,B Load the X position into A again.
DAD4 AND %00000111 Extract only the pixel offset within the character block.
DAD6 RRCA Multiply A by 20.
DAD7 RRCA
DAD8 RRCA
DAD9 ADD A,C Add the Y co-ordinate store the result in L.
DADA LD L,A
DADB RET Return.
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