Routines
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45878: Draw Rows
Used by the routine at DrawShot.
Draws rows of a buffer onto the screen by ORing them in, going up the screen from the row that HL is at. The number of rows is the value in 41432 and a row is B bytes of the buffer, which has eight bytes to a row.
Input
B Number of bytes in a row
DE Address of the buffer
HL Screen address
DrawRows 45878 LD A,B A=B.
45879 AND A Return if A is zero.
45880 RET Z
45881 LD C,B C=B.
45882 LD A,(41432) The rows to draw.
DrawRows_Row 45885 EX AF,AF' Switch to the alternate accumulator and flags.
45886 LD B,C B=C.
45887 PUSH DE Stash DE on the stack.
45888 PUSH HL Stash HL on the stack.
DrawRows_Byte 45889 LD A,(DE) Read DE.
45890 OR (HL) Set the bits of A that are set in the byte at HL.
45891 LD (HL),A Write A where HL points.
45892 INC L Advance L.
45893 INC DE Advance DE.
45894 DJNZ DrawRows_Byte Decrease B and jump to DrawRows_Byte until none remain.
45896 POP HL Bring HL back off the stack.
45897 CALL MoveUpARow Call MoveUpARow.
45900 POP DE Bring DE back off the stack.
45901 LD A,8 A=8.
45903 ADD A,E A gains E.
45904 LD E,A E=A.
45905 EX AF,AF' Switch to the alternate accumulator and flags.
45906 DEC A Step A back.
45907 JR NZ,DrawRows_Row Jump to DrawRows_Row if the zero flag is clear.
45909 RET Return.
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