PSSST: Routine at 75D0

75D0: Erase Sprite

Used by the routines at 74A5 and 751C.

Input
B	Loop counter
C	Actor Y position, or zero?
DE	Address into a sprite/buffer
HL	Address in the DISPLAY_FILE

MaskSprite

75D0

LD A,C

Jump to MaskSprite_4 if the sprites vertical position is zero.

75D1

AND A

75D2

JR Z,MaskSprite_4

75D4

DEC C

Else decrement.

75D5

PUSH BC

Stash BC and HL on the stack.

75D6

PUSH HL

Loop to create a mask of the sprite and it write to the screen.

MaskSprite_0

75D7

LD A,(DE)

A=sprite byte.

75D8

CPL

Create mask and write to screen.

75D9

AND (HL)

75DA

LD (HL),A

75DB

INC DE

Move onto the next byte.

75DC

INC L

Move onto the next column.

75DD

DJNZ MaskSprite_0

Decrease counter by one and loop back to MaskSprite_0 until counter is zero.

75DF

POP HL

Restore HL from the stack.

75E0

CALL ScreenPos1PixelAbove

Call ScreenPos1PixelAbove.

75E3

POP BC

Restore BC from the stack.

75E4

EXX

75E5

LD A,C

Jump to MaskSprite_3 if C is zero.

75E6

AND A

75E7

JR Z,MaskSprite_3

MaskSprite_1

75E9

DEC C

75EA

PUSH BC

Stash BC and HL on the stack.

75EB

PUSH HL

MaskSprite_2

75EC

LD A,(DE)

75ED

OR (HL)

75EE

LD (HL),A

75EF

INC DE

75F0

INC L

75F1

DJNZ MaskSprite_2

75F3

POP HL

Restore HL from the stack.

75F4

CALL ScreenPos1PixelAbove

Call ScreenPos1PixelAbove.

75F7

POP BC

Restore BC from the stack.

MaskSprite_3

75F8

EXX

75F9

JR MaskSprite

MaskSprite_4

75FB

EXX

75FC

LD A,C

75FD

AND A

75FE

JR NZ,MaskSprite_1

This entry point is used by the routine at 74A5.

MaskSprite_5

7600

EXX

This entry point is used by the routine at 74A5.

MaskSprite_6

7601

LD A,($5E10)

7604

LD C,A

7605

LD A,($5E11)

7608

OR C

7609

RET Z

760A

XOR A

760B

LD ($5E10),A

760E

EXX

760F

LD A,($5E11)

7612

LD C,A

7613

XOR A

This entry point is used by the routine at 74A5.

MaskSprite_7

7614

LD ($5E11),A

7617

EXX

7618

JR MaskSprite