Commodore 64 Manual do Utilizador descarregar pdf (Página 36)

If sprite pointer #0, at location 2040, contains the number 14, for

example, this means that sprite 0 will be displayed using the 64 bytes

beginning at location 14*64

= 896 which is in the cassette buffer. The

following formula makes this clear:

LOCATION

= (BANK * 16384) + (SPRITEPOINTERVALUE* 64)

Where BANK is the 16K segment of memory that the VIC-II chip is look-

ing at and is fr~m 0 to 3.

The above formula gives the start of the 64 bytes of the sprite

definition block.

When the VIC-II chip is looking at BANK0 or BANK 2, there is a ROM

IMAGE of the character set present in certain locations, as mentioned

before. Sprite definitions can NOT be placed there. If for some reason

you need more than 128 different sprite definitions, you should use one

of the banks without the ROM IMAGE, 1 or 3.

TURNING SPRITES ON

The VIC-II control register at location 53269 ($D015 in HEX) is known

as the SPRITE ENABLE register. Each of the sprites has a bit in this

looks like this:

$D015 7 6 5 4 3 2 1 0

To turn on sprite 1, for example, it is necessary to turn that bit to a I.

The following POKE does this:

POKE 53269,PEEK(53269)OR 2

A more general statement would be the following:

POKE 53269,PEEK(53269}OR (2tSN)

where SN is the sprite number, from 0 to 7.

NOTE: A sprite must be turned ON before it con be seen.

134 'PROGRAMMING GRAPHICS

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Commodore 64 Manual do Utilizador Página 36