Routines
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F8B9: Merge Background Byte
Used by the routine at BuildShiftedShapeB.
Merges one byte of the chequered background into the buffer: the pattern byte of 55, shifted by the amount that the table in D gives. The entry point at MergeBackgroundByte_Merge merges A.
Input
D Page of the table of shifted bytes
HL' Address in the buffer
Output
HL' Address of the next byte in the buffer
MergeBackgroundByte F8B9 LD E,$55 E=55.
F8BB LD A,(DE) Read DE.
This entry point is used by the routines at BuildShiftedShapeA and BuildShiftedShapeB.
MergeBackgroundByte_Merge F8BC EXX Switch to the alternate registers.
This entry point is used by the routine at BuildShiftedShapeA.
MergeBackgroundByte_Store F8BD OR (HL) Set the bits of A that are set in the byte at HL.
F8BE LD (HL),A Write A where HL points.
F8BF INC HL Advance HL.
F8C0 EXX Switch to the alternate registers.
F8C1 RET Return.
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