Routines
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B336: 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 A1D8 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 B336 LD A,B A=B.
B337 AND A Return if A is zero.
B338 RET Z
B339 LD C,B C=B.
B33A LD A,($A1D8) The rows to draw.
DrawRows_Row B33D EX AF,AF' Switch to the alternate accumulator and flags.
B33E LD B,C B=C.
B33F PUSH DE Stash DE on the stack.
B340 PUSH HL Stash HL on the stack.
DrawRows_Byte B341 LD A,(DE) Read DE.
B342 OR (HL) Set the bits of A that are set in the byte at HL.
B343 LD (HL),A Write A where HL points.
B344 INC L Advance L.
B345 INC DE Advance DE.
B346 DJNZ DrawRows_Byte Decrease B and jump to DrawRows_Byte until none remain.
B348 POP HL Bring HL back off the stack.
B349 CALL MoveUpARow Call MoveUpARow.
B34C POP DE Bring DE back off the stack.
B34D LD A,$08 A=08.
B34F ADD A,E A gains E.
B350 LD E,A E=A.
B351 EX AF,AF' Switch to the alternate accumulator and flags.
B352 DEC A Step A back.
B353 JR NZ,DrawRows_Row Jump to DrawRows_Row if the zero flag is clear.
B355 RET Return.
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