Routines
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6653: Find Sprite Frame
Used by the routines at SetEntitySize and DrawSprite.
Finds the address of the sprite which shows an entity. The type of the entity selects a table of frames and the frame number of the entity selects one of the sprites in that table.
Input
IX The entity
Output
DE The address of the sprite
FindSpriteFrame 6653 LD E,(IX+$00) Fetch the type of the entity.
6656 LD D,$00 Clear D.
6658 LD HL,$669E Point HL at SpriteTable.
665B ADD HL,DE Add the type twice, as the table has two bytes per entry.
665C ADD HL,DE
665D LD E,(HL) Fetch the low byte of the address of the frame table of the type.
665E INC HL Move onto the high byte.
665F LD D,(HL) Fetch the high byte of the address of the frame table.
6660 LD A,(IX+$01) Fetch the frame number of the entity.
6663 AND %00011111 Keep the frame number in the range 00-1F.
6665 ADD A,A Double it, as the table has two bytes per frame.
6666 LD L,A Set HL to the frame number multiplied by two.
6667 LD H,$00 Clear the high byte.
6669 ADD HL,DE Add the address of the frame table to find the address of the entry.
666A LD E,(HL) Fetch the low byte of the address of the sprite.
666B INC HL Move onto the high byte.
666C LD D,(HL) Fetch the high byte of the address of the sprite.
666D RET Return.
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