Chapter 1 Functions of VDP2

VDP2 has scrolling and priority features. The scroll function defines a scroll screen and moves the screen up / down / left / right or rotates. The priority function is a function that determines the display priority of multiple scroll screens, sprites, and external screens, and performs image processing such as color calculation and color offset.

■ 1.1 System configuration

VDP2 has 4M or 8Mbit VRAM connected and 32Kbit color RAM built-in. Image data is defined in VRAM and color RAM from the CPU via the SCU. The information that controls the image display is also set in each register in the same way.
The data defined in VRAM is read according to the register settings and becomes the image data of each scroll screen. The display priority of the image data of each scroll screen, the sprite image data sent from VDP1, and the external image data sent from the outside is determined according to the register settings, and becomes the display image data. When the display image data is in palette format, the color data defined in the color RAM is read according to the value and used as the display color data. When the display image data is in RGB format, the display image data is used as the display color data as it is. The display color data obtained in this way is output to the display device.
Figure 1.1 shows the VDP2 system configuration.

Figure 1.1 System configuration