<75/86> VDP2 User's Manual / 15.2 How to use RAM

★ HARDWARE Manual ★ VDP2 User's Manual ★ Chapter 15 How to use VDP2

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VDP2 User's Manual / Chapter 15 How to use VDP2

■ 15.2 How to use RAM

When using VDP2, define and set data in VRAM, color RAM, and registers.

● VRAM

The data defined in VRAM differs depending on the scroll screen used, screen format, screen size, and image processing function used. Define each data in VRAM according to the register settings, and set the defined addresses in the address register. Table 15.1 shows the main registers associated with the data defined in VRAM.

Table 15.1 Registers associated with the data defined in VRAM

data What to define Related registers Data to set Pattern name table Start address of character pattern Pattern name control register (Body / Reference) ・ Pattern name data size ・ Character number auxiliary mode ・ Pattern name auxiliary data Plain size register (Body / Reference) -Plain size when displaying in cell format Normal scroll screen map register (Body / Reference) -Start address of the pattern name table to be placed on each plane Rotation scroll screen map register (Body / Reference) -Start address of the pattern name table to be placed on each plane Map offset register (Body / Reference) -A 3-bit map offset value attached to the upper level of the map register Character pattern Cell dot data Character control register (Body / Reference) ・ Number of character colors and character size Bitmap pattern Bitmap pattern data Character control register (Body / Reference) -Number of character colors (number of bitmap colors) -Bitmap size-Bitmap enabled Map offset register (Body / Reference) -Boundary address of bitmap pattern Line scroll table Horizontal and vertical screen scroll values, Horizontal coordinate increment Line scroll table address register (Body / Reference) -Start address of line scroll table Line & Vertical Cell Scroll Control Register (Body / Reference) -Scroll function control data Vertical cell scroll table Vertical screen scroll value Vertical cell scroll table address register (Body / Reference) -Start address of vertical cell scroll table Line & Vertical Cell Scroll Control Register (Body / Reference) -Scroll function control data Rotation parameter table Rotation parameters, Related registers in the coefficient table RAM control register (Body / Reference) -Purpose of using VRAM on the rotary scroll screen Rotation parameter table address register (Body / Reference) -Starting address of parameter table Rotation parameter mode register (Body / Reference) -Specify rotation parameter mode Coefficient table Coefficient table data (magnification / reduction coefficients kx, ky, Start point coordinates after rotation conversion Xp) RAM control register (Body / Reference) -Purpose of using VRAM on the rotary scroll screen Coefficient table control register (Body / Reference) ・ Coefficient data mode ・ Data size of coefficient data ・ Coefficient table enabled Coefficient table address offset register (Body / Reference) -Start address offset value of coefficient table Line color screen table Color RAM address Line color screen table address register (Body / Reference) -Color mode of line color screen-Start address of line color screen table Back screen table RGB color data Back screen table address register (Body / Reference) -Back screen color mode-Back screen table start address Line window table Horizontal start point coordinates, Horizontal end point coordinates Line window table address register (Body / Reference) -Line window enable-Start address of line window table

● Definition of color RAM

data	What to define	Related registers	Data to set
Pattern name table	Start address of character pattern	Pattern name control register (Body / Reference)	・ Pattern name data size ・ Character number auxiliary mode ・ Pattern name auxiliary data
Plain size register (Body / Reference)	-Plain size when displaying in cell format
Normal scroll screen map register (Body / Reference)	-Start address of the pattern name table to be placed on each plane
Rotation scroll screen map register (Body / Reference)	-Start address of the pattern name table to be placed on each plane
Map offset register (Body / Reference)	-A 3-bit map offset value attached to the upper level of the map register
Character pattern	Cell dot data	Character control register (Body / Reference)	・ Number of character colors and character size
Bitmap pattern	Bitmap pattern data	Character control register (Body / Reference)	-Number of character colors (number of bitmap colors) -Bitmap size-Bitmap enabled
Map offset register (Body / Reference)	-Boundary address of bitmap pattern
Line scroll table	Horizontal and vertical screen scroll values, Horizontal coordinate increment	Line scroll table address register (Body / Reference)	-Start address of line scroll table
Line & Vertical Cell Scroll Control Register (Body / Reference)	-Scroll function control data
Vertical cell scroll table	Vertical screen scroll value	Vertical cell scroll table address register (Body / Reference)	-Start address of vertical cell scroll table
Line & Vertical Cell Scroll Control Register (Body / Reference)	-Scroll function control data
Rotation parameter table	Rotation parameters, Related registers in the coefficient table	RAM control register (Body / Reference)	-Purpose of using VRAM on the rotary scroll screen
Rotation parameter table address register (Body / Reference)	-Starting address of parameter table
Rotation parameter mode register (Body / Reference)	-Specify rotation parameter mode
Coefficient table	Coefficient table data (magnification / reduction coefficients kx, ky, Start point coordinates after rotation conversion Xp)	RAM control register (Body / Reference)	-Purpose of using VRAM on the rotary scroll screen
Coefficient table control register (Body / Reference)	・ Coefficient data mode ・ Data size of coefficient data ・ Coefficient table enabled
Coefficient table address offset register (Body / Reference)	-Start address offset value of coefficient table
Line color screen table	Color RAM address	Line color screen table address register (Body / Reference)	-Color mode of line color screen-Start address of line color screen table
Back screen table	RGB color data	Back screen table address register (Body / Reference)	-Back screen color mode-Back screen table start address
Line window table	Horizontal start point coordinates, Horizontal end point coordinates	Line window table address register (Body / Reference)	-Line window enable-Start address of line window table

Defines color data for palette-style sprites and scroll screens. The color data stored in the color RAM is in RGB format and has three modes. The mode selection is specified by the color RAM mode (CRMD1, CRMD0, bits 13, 12) of the RAM control register (18000EH).

The most significant bit of the color data stored in the color RAM is the enable bit when the special color calculation mode is mode 3. When the special color calculation mode is mode 3, the color format is palette format, and the color calculation enable bit is 1, color calculation is performed in dot units for dots using color data with the most significant bit of 1. increase.

● Reference to color RAM

Color RAM is referenced from character patterns, bitmap patterns, and line color screen table data. The color RAM address is represented by 11 bits. If the number of character colors or bitmap colors is 16, the upper 7-bit palette number is added to make it 11 bits, and if it is 256 colors, the upper 3 bit palette number is added to make it 11 bits. increase. The palette number of the character pattern is in the pattern name data and the auxiliary data of the pattern name control register, and the palette number of the bitmap pattern is in the bitmap palette number register.

● Register

Registers are, in principle, write-only 16-bit registers that specify VDP2 functionality. In some cases, one function spans several registers, and in other cases, several functions are grouped in one register.
Set the register corresponding to the function to be used as necessary.

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★ HARDWARE Manual ★ VDP2 User's Manual ★ Chapter 15 How to use VDP2