Chapter 9 Sprite data

9.1 Sprite data

The frame buffer data of the sprite received from VDP1 can be 8 bits or 16 bits per dot. For 16 bits per dot, some are written in palette format and others are written in RGB format. Set them on the VDP2 side in the same way as when setting them on the VDP1 side.

Sprite type

When VDP2 receives palette-type sprite data written by VDP1 into the frame buffer, there are 16 bit configurations, 8 for 16 bits per dot and 8 for 8 bits. Is called a sprite type. The data per dot consists of dot color data consisting of a dot color code and palette number, priority bits, color calculation ratio bits, and shadow bits, and the number of each bit varies depending on the sprite type. For each bit, the value of the missing high-order bit is considered to be 0.
In addition, when the sprite data is in RGB format, it consists of RGB data of 5 bits each and color format identification bit, and the priority bit, color calculation ratio bit, and shadow bit are regarded as 0.
Specify type 0 to 7 when sprite data is 16 bits per dot, and type 8 to F when 8 bits per dot. In addition, when type C to F is specified, there are bits that share the bits for priority and color calculation ratio and the bits of dot color data. Table 9.1 shows the shared bits.

Table 9.1 Shared bits

Sprite type	Shared bit
	SP1	SP0	SC1	SC0
Type C	-	PR0 and DC7	−	−
Type D	-	PR0 and DC7	−	CC0 and DC6
Type E	PR1 and DC7	PR0 and DC6	-	-
Type F	-	-	CC1 DC7	CC0 and DC6

SP: Priority bit, Color RAM address shared bit
SC: Color calculation ratio bit, color RAM address shared bit
PR: Priority bit
DC: Dot color data
CC: Color calculation ratio bit