SPRITE CONTROL WORD 1: SPRxPOS
This word contains the vertical (VSTART) and horizontal (HSTART) starting position for the
sprite. This is where the topmost line of the sprite will be positioned.
Bits 15-8 contain the low 8 bits of VSTART
Bits 7-0 contain the high 8 bits of HSTART
SPRITE CONTROL WORD 2: SPRxCTL
This word contains the vertical stopping position of the sprite on the screen (i.e., the line
AFTER the last displayed row of the sprite). It also contains some data having to do with
sprite attachment, which is described later on.
SPRxCTL
Bits 15-8 The low eight bits of VSTOP
Bit 7 (Used in attachment)
Bits 6-3 Unused (make zero)
Bit 2 The VSTART high bit
Bit 1 The VSTOP high bit
Bit 0 The HSTART low bit
The value (VSTOP - VSTART) defines how many scan lines high the sprite will
be when it is displayed.
SPRITE COLOR DESCRIPTOR WORDS
It takes two color descriptor words to describe each horizontal line of a sprite; the high-
order word and the low-order word. To calculate how many color descriptor words you
need, multiply the height of the sprite in lines by 2. The bits in the high-order color
descriptor word contribute the left most digit of the binary color selector number for each
pixel; the low-order word contributes the rightmost digit.
- 104 Sprite Hardware -
To Next Page
Loading...
