Commodore 64 Manual de usuario descargar pdf (Pagina 39)

To unexpand a sprite in the horizontal direction, the corresponding bit

in the VIC-II control register at location 53277 ($DOID in HEX) must be

turned OFF (set to a 0). The following POKE "unexpands" a sprite in the

X direction:

POKE 53277,PEEK(53277)AND (255-2tSN)

where SN is the sprite number from 0 to 7.

To expand a sprite in the vertical direction, the corresponding bit in

the VIC-II control register at location 53271 ($DOI7 in HEX) must be

turned ON (set to a 1). The following POKE expands a sprite in the Y

direction:

POKE 53271, PEEK{53271)OR (2tSN)

where SN is the sprite number from 0 to 7.

To unexpand a sprite in the vertical direction, the corresponding bit in

the VIC-II control register at location 53271 ($DOI7 in HEX) must be

turned OFF (set to a 0). The following POKE "unexpands" a sprite in the

Y direction:

POKE 53271,PEEK(53271)AND (255-2tSN)

where SN is the sprite number from 0 to 7.

SPRITE

POSITIONING

Once you've made a sprite you want to be able to move it around the

screen. To do this, your Commodore 64 uses three positioning registers:

1) SPRITE X POSITION REGISTER

2) SPRITE Y POSITION REGISTER

3) MOST SIGNIFICANT BIT X POSITION REGISTER

Each sprite has an X position register, a Y position register, and a bit

in the X most significant bit register. This lets you position your sprites

very accurately. You can place your sprite in 512 possible X positions

and 256 possible Y positions.

The X and Y position registers work together, in pairs, as a team. The

locatkms of the X and Y registers appear in the memory map as follows:

First is the X register for sprite 0, then the Y register for sprite O. Next

PROGRAMMINGGRAPHICS 137

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Commodore 64 Manual de usuario Pagina 39