Routines
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E63A: Draw Intro UDG
Used by the routine at Animate_Introduction.
Draws a two-column, two-row UDG from *HL to the screen at *DE. The introduction uses this for the moon and bat frames.
Input
HL Graphic data
DE Screen address
Draw the upper character row.
Draw_IntroUDG E63A LD B,$08 Set the pixel-row counter to 08.
E63C PUSH DE Stash the screen address on the stack.
Draw_IntroUDG_Upper E63D LD A,(HL) Write the left-hand pixel byte to the screen.
E63E LD (DE),A
E63F INC HL Advance the graphic pointer and move to the next column.
E640 INC E
E641 LD A,(HL) Write the right-hand pixel byte to the screen.
E642 LD (DE),A
E643 DEC E Move back to the left-hand column.
E644 INC D Move down one pixel row.
E645 INC HL Advance the graphic pointer.
E646 DJNZ Draw_IntroUDG_Upper Decrease the pixel-row counter by one and jump to Draw_IntroUDG_Upper until all eight rows are drawn.
Move down one character row.
E648 POP DE Restore the original screen address from the stack.
E649 LD A,$20 Add 20 to the screen address.
E64B ADD A,E
E64C LD E,A
E64D LD B,$08 Set the pixel-row counter to 08.
Draw the lower character row.
Draw_IntroUDG_Lower E64F LD A,(HL) Write the left-hand pixel byte to the screen.
E650 LD (DE),A
E651 INC HL Advance the graphic pointer and move to the next column.
E652 INC E
E653 LD A,(HL) Write the right-hand pixel byte to the screen.
E654 LD (DE),A
E655 INC HL Advance the graphic pointer.
E656 DEC E Move back to the left-hand column.
E657 INC D Move down one pixel row.
E658 DJNZ Draw_IntroUDG_Lower Decrease the pixel-row counter by one and jump to Draw_IntroUDG_Lower until all eight rows are drawn.
E65A RET Return.
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