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Chapter 5 VGA ------- **************************************** * * ****** INTRODUCTION ******** * * **************************************** A. VIDEO MODE : 1. Text mode 2. Graphics mode B. DISPLAY MEMORY ORGANIZATION C. CHARACTER GENERATOR D. COLOR PALETTE AND COLOR REGISTER E. GRAPHICS READ AND WRITE MODES 1. Write modes : 0-3 2. Read modes : 0-1 F. VGA REGISTER 1. General or External registers 2. Sequencer registers 3. CRTC registers 4. Graphics registers 5. Attribute registers G. VGA BIOS DATA AREA H. VIDEO POST SEQUENCE I. VIDEO BIOS SERVICE ROUTINES ************************************ * * ******* TEXT MODES ******* * * ************************************ ┌────────────────────────────────────────────────────────────────────┐ │ Mode #chars Display page Resolution Buffer │ │ (X/Y) Char Box Format no. in Pixels │ ├────────────────────────────────────────────────────────────────────│ │ 0,1 40/25 8 x 8 16/256K 8 320 x 200 B8000 │ ├────────────────────────────────────────────────────────────────────│ │ 0*,1* 40/25 8 x 14 16/256K 8 320 x 350 B8000 │ ├────────────────────────────────────────────────────────────────────│ │ 0+,1+ 40/25 8 x 16 16/256K 8 320 x 400 B8000 │ ├────────────────────────────────────────────────────────────────────│ │ 2,3 80/25 8 x 8 16/256K 8 640 x 200 B8000 │ ├────────────────────────────────────────────────────────────────────│ │ 2*,3* 80/25 8 x 14 16/256K 8 640 x 350 B8000 │ ├────────────────────────────────────────────────────────────────────│ │ 2+,3+ 80/25 8 x 16 16/256K 8 640 x 400 B8000 │ ├────────────────────────────────────────────────────────────────────│ │ 7 80/25 9 x 14 bw 8 720 x 350 B0000 │ ├────────────────────────────────────────────────────────────────────│ │ 7+ 80/25 9 x 16 bw 8 720 x 400 B0000 │ └────────────────────────────────────────────────────────────────────┘ Note: 1. The asterisk (*) in the display mode indicates that VGA is in a text mode with 350 vertical lines. 2. The plus (+) in the display mode indicates that VGA is in a text mode with 400 vertical lines. 3. Display modes 0 through 6 emulate the Color Graphics Adapter(CGA). Mode 7 emulates the IBM Monochrome MDA or Hercules Monochrome graphics. 4. The code "bw" stands for black and white or synonymously monochrome. ************************************ * * ******* GRAPHICS MODES ******* * * ************************************ ┌────────────────────────────────────────────────────────────────────┐ │ Mode #chars Display page Resolution Buffer │ │ (Hex) (X/Y) Char Box Format no. in Pixels │ ├────────────────────────────────────────────────────────────────────│ │ 4,5 40/25 8 x 8 4/256K 1 320 x 200 B8000 │ ├────────────────────────────────────────────────────────────────────│ │ 6 80/25 8 x 8 2/256K 1 640 x 350 B8000 │ ├────────────────────────────────────────────────────────────────────│ │ D 40/25 8 x 8 16/256K 8 320 x 200 A0000 │ ├────────────────────────────────────────────────────────────────────│ │ E 80/25 8 x 8 16/256K 4 640 x 200 A0000 │ ├────────────────────────────────────────────────────────────────────│ │ F 80/25 8 x 14 bw 2 640 x 350 A0000 │ ├────────────────────────────────────────────────────────────────────│ │ 10 80/25 8 x 14 16/256K 2 640 x 350 A0000 │ ├────────────────────────────────────────────────────────────────────│ │ 11 80/30 8 x 16 2/256K 1 640 x 480 A0000 │ ├─────────────────────────────────────────────────────────────────── │ │ 12 80/30 8 x 16 16/256K 1 640 x 480 A0000 │ ├────────────────────────────────────────────────────────────────────┤ │ 13 40/25 8 x 8 256/256K 1 320 x 200 A0000 │ └────────────────────────────────────────────────────────────────────┘ ┌────────────────────────────────────────────────────────────────────────┐ │ MODE │ │ (Hex) # of Colors # Bits per Plane Bit Planes Affected Notes │ ├────────────────────────────────────────────────────────────────────────┤ │ 4,5 4 2 0,1 1 │ ├────────────────────────────────────────────────────────────────────────│ │ 6 2 1 0 2 │ ├────────────────────────────────────────────────────────────────────────│ │ D 16 1 0,1,2,3 3 │ ├────────────────────────────────────────────────────────────────────────│ │ E 16 1 0,1,2,3 3 │ ├────────────────────────────────────────────────────────────────────────│ │ F 4 1 0,2 4 │ ├────────────────────────────────────────────────────────────────────────│ │ 10 16 1 0,1,2,3 3 │ ├────────────────────────────────────────────────────────────────────────│ │ 11 2 1 0 2 │ ├────────────────────────────────────────────────────────────────────────│ │ 12 16 1 0,1,2,3 3 │ ├────────────────────────────────────────────────────────────────────────┤ │ 13 256 8 0,1,2 or 3 5 │ └────────────────────────────────────────────────────────────────────────┘ Notes: 1.In modes 4 and 5, alternate bytes of data, each containing four pixels, are stored in bit plane 0 and bit plane 1. Bit plane 0 contributes the low-order bit, and bit plane 1 contributes the high-order bit of the two-bit pixel. 2.In modes 6 and 11 hex, each pixel consists of one bit in bit plane 0. 3.In mode D,E,10,12 hex, each pixel corresponds to one bit in each of the four bit planes. Bit plane 0 contributes the low-order bit, followed by bit plane 1, and bit plane 2. Bit plane 3 contributes the high-order bit of the four bit pixel. 4.In mode F hex, bit plane 0 contributes the low-order bit and bit plane 2 contributes the high-order bit of the two bit pixel. 5.In mode 13 hex, all four bit planes are chained together and each pixel consists of eight bits. The plane in which a pixel resides depends on the position of the pixel on the display. Each plane holds one-quarter of the pixels. ************************************ * * ******* CHARACTER FONTS ******* * * ************************************ There are 5 character fonts set supported: 8 by 8 ,8 by 14, 8 by 16, 9 by 14, and 9 by 16. ASCII_8X8 db 00H,00H,00H,00H,00H,00H,00H,00H ;ASCII 0 db 07EH,081H,0A5H,081H,0BDH,099H,081H,7EH ;ASCII 1 db 07CH,0FEH,0D6H,0FEH,0C6H,0FEH,07CH,00H ;ASCII 2 db 06CH,0FEH,0FEH,0FEH,07CH,038H,010H,00H ;ASCII 3 db 010H,038H,07CH,0FEH,07CH,038H,010H,00H ;ASCII 4 db 010H,038H,054H,0FEH,054H,010H,07CH,00H ;ASCII 5 . . . ASCII_8X8_1 db 07CH,0C0H,0C6H,07CH,018H,0CH,078H,00H ;ASCII 128 db 06CH,00H,0CCH,0CCH,0CCH,0CCH,076H,00H ;ASCII 129 db 0CH,018H,03CH,066H,07EH,060H,03EH,00H ;ASCII 131 db 038H,044H,078H,0CH,07CH,0CCH,076H,00H ;ASCII 132 db 06CH,00H,078H,0CH,07CH,0CCH,076H,00H ;ASCII 133 db 030H,018H,078H,0CH,07CH,0CCH,076H,00H ;ASCII 134 db 038H,044H,078H,0CH,07CH,0CCH,076H,00H ;ASCII 135 . . . ASCII_8X14 db 00H,00H,00H,00H,00H,00H,00H,00H,00H db 00H,00H,00H,00H,00H ;ASCII 0 db 00H,00H,07EH,081H,0A5H,081H,081H,0BDH db 099H,081H,07EH,00H,00H,00H ;ASCII 1 db 0H,00H,07EH,0FFH,0DBH,0FFH,0FFH,0C3H db 0E7H,0FFH,07EH,00H,00H,00H ;ASCII 2 db 00H,00H,00H,06CH,0FEH,0FEH,0FEH,0FEH db 07CH,038H,010H,00H,00H,00H ;ASCII 3 db 00H,00H,00H,010H,038H,07CH,0FEH,07CH db 038H,010H,00H,00H,00H,00H ;ASCII 4 . . . ASCII_8X16 db 00H,00H,00H,00H,00H,00H,00H db 00H,00H,00H,00H,00H,00H,00H,00H,00H ;ASCII 0 db 00H,00H,07EH,081H,0A5H db 081H,081H,0BDH,099H,081H,081H db 07EH,00H,00H,00H,00H ;ASCII 1 db 00H,00H,07EH,0FFH,0FFH db 0DBH,0FFH,0FFH,0C3H,0E7H db 0FFH,07EH,00H,00H,00H,00H ;ASCII 2 db 00H,00H,00H,00H,06CH,0FEH db 0FEH,0FEH,0FEH,07CH,038H db 010H,00H,00H,00H,00H ;ASCII 3 . . . ; ; 12 additional character of 8X14 ; ASCII_9X14 db 1dh,0H,00H,00H,00H,024H,066H,0FFH db 066H,024H,00H,00H,00H,00H,00H ;code 1dh db 4dh,00H,00H,0C3H,0E7H,0FFH,0DBH db 0C3H,0C3H,0C3H,0C3H,0C3H,00H,00H,00H ;code 4dh db 54h,00H,00H,0FFH,0DBH,099H,018H,018H db 018H,018H,018H,03CH,00H,00H,00H ;code 54h db 56h,00H,00H,0C3H,0C3H,0C3H,0C3H . . . ASCII_9X16 db 1dh,00H,00H,00H,00H,00H,024H,066H db 0FFH,066H,024H,00H,00H,00H,00H,00H,00H ;code 1dh db 4dh,00H,00H,0C3H,0E7H,0FFH,0DBH,0C3H db 0C3H,0C3H,0C3H,0C3H,0C3H,00H,00H,00H,00H ;code 4dh db 54h,00H,00H,0FFH,0DBH,099H,018H,018H,018H db 018H,018H,018H,03CH,00H,00H,00H,00H ;code 54h db 56h,00H,00H,0C3H,0C3H,0C3H,0C3H,0C3H,0C3H db 0C3H,066H,03CH,018H,00H,00H,00H,00H ;code 56h db 57h,00H,00H,0C3H,0C3H,0C3H,0C3H,0C3H,0DBH db 0DBH,0DBH,0FFH,066H,00H,00H,00H,00H ;code 57h . . . The 9 by 14 and 9 by 16 character font are referred to as the supplement character set. It is called supplemental because not all of the 256 characters are provided. Typical characters that are included in the supplement are quotation marks ("),the plus sign (+),the minus sign (-), M,T,V,W,X,Y,Z,m,v,w,and line-drawing symbols. ************************************ * * **** CHARACTER ATTRIBUTE **** * * ************************************ A. MONOCHROME MODE Mode 7: Monochrome Attributes ────────────────────────────────────────────────────────────────────── Background Forground Attribute (bit3 6-4) (bits 2-0) ────────────────────────────────────────────────────────────────────── 0 0 Black 0 1 Underline 0 7 Normal(white on black) 7 0 Reversed(black on white) 7 7 White Mode 7: Examples of Monochrome Attributes ──────────────────────────────────────────────────────────────────────── Blink Background Intens Forground Code (Bit 7) (bits 6-4) (Bit 3) (Bit 2-0) (Hex) Attribute ──────────────────────────────────────────────────────────────────────── 0 0 0 1 1 Underline 0 0 1 1 9 Intense Underline 0 7 0 0 70 Reversed 0 7 1 0 74 Intense Reversed 1 7 0 0 F0 Blinking Reversed 1 7 1 0 F1 Intense Blinking Reserved Mode 7: Palette Registers ─────────────────────────────────────────────────────────────────────── Register # Register Value Register # Register Value ─────────────────────────────────────────────────────────────────────── 0 00 8 10 1 08 9 18 2 08 A 18 3 08 B 18 4 08 C 18 5 08 D 18 6 08 E 18 7 08 F 18 B. SIXTEEN-COLOR MODE Default Colors for a 16-color Palette ──────────────────────────────────────────────── Palette Register (Hex) Color ──────────────────────────────────────────────── 0 Black 1 Blue 2 Green 3 Cyan 4 Red 5 Magenta 6 Brown 7 White 8 Gray 9 Light Blue A Light Green B Light cyan C Light red D Light Magenta E Light Brown (yellow) F Bright White C. ATTRIBUTE BYTE IN THE 16-COLOR MODE 7 6 5 4 3 2 1 0 ┌──────────────────────┬──────────────────────┐ │ │ │ └──────────────────────┴──────────────────────┘ Background Forground 7 6 5 4 3 2 1 0 ┌──────────────────────┬────┬─────────────────┐ │ │ │ │ └──────────────────────┴─┼──┴─────────────────┘ Background │ Forground Font # 7 6 5 4 3 2 1 0 ┌───┬──────────────────┬──────────────────────┐ │ │ │ │ └─┼─┴──────────────────┴──────────────────────┘ │ Background Forground Blinking 7 6 5 4 3 2 1 0 ┌───┬──────────────────┬───┬──────────────────┐ │ │ │ │ │ └─┼─┴──────────────────┴─┼─┴──────────────────┘ │ Background │ Forground Blinking Font # Note: 1. The character attribute byte is used to determine the character color, to determine the blinking status, and to select from one of the two character sets. Bit 3 of the character attribute byte is used either to select one of 16 forground colors for the associated character or to choose from one of two resident character sets. Bit 7 is selected to have dual function of either being part of the background color code or being a switch for the blinking feature. 2. The default alphanumeric characters are defined by the bit patterns in the first table in MAP 2, regardless of the value of bit 3 of the attribute bytes of the characters displayed. Changing the value in the Character Map Select register, changes the character definition tables associated with bit 3 of attribute bytes. If two different values appear in the bit fields in the Character Map Select register, the value of bit 3 designates one of two different character definition tables. ************************************ * * ******* VGA REGISTERS ****** * * ************************************ General or External Registers ────────────────────────────────────────────────────────────────────────── Name Write (Hex) Read (Hex) Misc. Output 3C2 3CC Feature Control 3DA/3BA 3CA Input Status #0 3C2 Input Status #1 3DA/3BA ────────────────────────────────────────────────────────────────────────── Sequencer Registers ───────────────────────────────────────────────────────────────────────── Name Index R/W Port(Hex) Address x 3C4 Reset 0 3C5 Clocking Mode 1 3C5 Map Mask 2 3C5 Character Map Select 3 3C5 Memory Mode 4 3C5 ───────────────────────────────────────────────────────────────────────── Attribute Controller Registers ───────────────────────────────────────────────────────────────────────── Name Index R/W Port(Hex) Address x 3C0 Palette 0-F 3C1 Mode Control 10 3C1 Overscan Color 11 3C1 Color Plane Enable 12 3C1 Horizontal Pixel Panning 13 3C1 Color Select 14 3C1 ───────────────────────────────────────────────────────────────────────── Graphics Control Registers: ───────────────────────────────────────────────────────────────────────── Name Index R/W Port(Hex) Graphics Address x 3CE Set/Reset 0 3CF Enable Set/Reset 1 3CF Color Compare 2 3CF Data Rotate 3 3CF Read Map Select 4 3CF Mode 5 3CF Miscellaneous 6 3CF Color Don't Care 7 3CF Bit Mask 8 3CF ──────────────────────────────────────────────────────────────────────── CRT Controller Registers ──────────────────────────────────────────────────────────────────────── Name Index R/W Port(Hex) Address x 3D4/3B4 Horizontal Total 0 3D5/3B5 Horizontal Display End 1 3D5/3B5 Start Horizontal Blank 2 3D5/3B5 End Horizontal Blank 3 3D5/3B5 Start Horizontal Retrace 4 3D5/3B5 End Horizontal Retrace 5 3D5/3B5 Vertical Total 6 3D5/3B5 Overflow 7 3D5/3B5 Preset Row Scan 8 3D5/3B5 Max Scan Line 9 3D5/3B5 Cursor Start A 3D5/3B5 Cursor End B 3D5/3B5 Start Address High C 3D5/3B5 Start Address Low D 3D5/3B5 Cursor Location High E 3D5/3B5 Cursor Location Low F 3D5/3B5 Vertical Retrace Start 10 3D5/3B5 Vertical Retrace Low 11 3D5/3B5 Vertical Display End 12 3D5/3B5 Offset 13 3D5/3B5 Underline Location 14 3D5/3B5 Start Vertical Blank 15 3D5/3B5 End Vertical Blank 16 3D5/3B5 Mode Control 17 3D5/3B5 Line Compare 18 3D5/3B5 ──────────────────────────────────────────────────────────────────────── ************************************ * * ******* MEMORY MAPPING ****** * * ************************************ The video buffer can be configured as the following : 1). A000:0 ------- 128K for mode D,E,F,10,11,12 and 13 2). A000:0 ------- 64K for character generator for text modes 3). B000:0 ------- 32k for mode 7 and 7+ 4). B800:0 ------- 32K for text mode 0,1,2,3 and graphics modes 4,5,6 ************************************ * * ******* CHARACTER GENERATOR ****** * * ************************************ The character generator consists of the dot patterns that represent each character in the character set. The character dot patterns are stored in character boxes, each of which is 32 bytes long. Bits set to 1 in the character font will be displayed in the forground color, and bits reset to 0 will be displayed in the background color. The display memory consists of four display planes called bit planes, each being 64K bytes long. VGA supports eight font tables. Each table consists of 256 32-byte bit patterns, so the character box height is 32 scan lines. When the displayed character box contains fewer than 32 lines, the character generator ignored the extra bytes in each character definition. The character generator has 8 blocks illustrated in the following: A000:0 ╔═════════╗ ┌────────────────────┐ ║ Font 0 ─╫───────── 0 │ 0 │ 2000 ╟─────────║ ├────────────────────│ ║ Font 4 ║ 1 │ 1 │ 4000 ╠═════════╣ ├────────────────────│ character 0 ║ Font 1 ║ │ . │ 6000 ╟─────────║ │ . │ ║ Font 5 ║ │ . │ 8000 ╠═════════╣ ├────────────────────│ ║ Font 2 ║ 31 │ 31 │ A000 ╟─────────║ ─────┼────────────────────┼───────── ║ Font 6 ║ 32 │ 0 │ C000 ╠═════════╣ ├────────────────────│ ║ Font 3 ║ 33 │ 1 │ E000 ╟─────────║ ├────────────────────│ ║ Font 7 ║ │ . │ ╚═════════╝ │ . │ character 1 │ . │ │────────────────────│ 63 │ 31 │ ─────┼────────────────────┼───────── 64 │ . │ . │ . │ . │ . │ . ────┼────────────────────┼────────── │ 0 │ ├────────────────────│ │ │ │ │ character 255 ├────────────────────┤ 8191 │ 31 │ └────────────────────┘ *************************************************** * * ******* GRAPHICS MODES PIXEL PROGRAMMING ****** * * *************************************************** A. Relative Registers Accessed: Graphics Control Registers: Name Index R/W Port(Hex) Graphics Address x 3CE Set/Reset 0 3CF Enable Set/Reset 1 3CF Color Compare 2 3CF Data Rotate 3 3CF Read Map Select 4 3CF Mode 5 3CF Miscellaneous 6 3CF Color Don't Care 7 3CF Bit Mask 8 3CF B. Read/Write Mode 1. Write Mode 0 (EGA/VGA) 2. Write Mode 1 (EGA/VGA) 3. Write Mode 2 (EGA/VGA) 4. Write Mode 3 (VGA Only) 5. Read Mode 0 (EGA/VGA) 6. Read Mode 1 (EGA/VGA) *************************************** * * ******* PALETTE/COLOR REGISTER ****** * * *************************************** Palette Utilization ─────────────────────────────────────────────────────────────────────── Display Mode (hex) Number of Colors Palette Register Affected 0,1 16 0-15 2,3 16 0-15 4,5 4 0,1,2,3 6 2 0,1 7 4 0,1,4,5 D 16 0-15 E 16 0-15 F 4 0,1,4,5 10 16 0-15 11 2 0,1 12 16 0-15 13 256 0-15 Mode 7 Palette Defult Values ────────────────────────────────────────────────────────── Register 0 1 2 3 4 5 6 7 8 9 A B C D E F Value 0 8 8 8 8 8 8 8 10 18 18 18 18 18 18 18 ─────────────────────────────────────────────────────────── Mode F Palette Default Values ────────────────────────────────────────────────────────── Register 0 1 2 3 4 5 6 7 8 9 A B C D E F Value 0 8 - - 18 18 - - - - - - - - - - ─────────────────────────────────────────────────────────── Mode 0,1,2,3 Palette Default Values ( 200 scan line) ────────────────────────────────────────────────────────── Register 0 1 2 3 4 5 6 7 8 9 A B C D E F Value 0 1 2 3 4 5 14 7 38 39 3A 3B 3C 3D 3E 3F ─────────────────────────────────────────────────────────── Mode 0*,1*,2*,3* Palette Default Values ( 350, 400 ) ────────────────────────────────────────────────────────── Register 0 1 2 3 4 5 6 7 8 9 A B C D E F Value 0 1 2 3 4 5 6 7 10 11 12 13 14 15 16 17 ─────────────────────────────────────────────────────────── CGA-compatible Color Selection ──────────────────────────────────────────────────────────────── ATR 1 ATR 0 Set 1 Set 0 VGA Palette Register 0 0 Background Background 0 0 1 Cyan Green 1 1 0 Magenta Red 2 1 1 White Brown 3 Mode 6 Palette Default Values ────────────────────────────────────────────────────────── Register 0 1 2 3 4 5 6 7 8 9 A B C D E F Value 0 17 17 17 17 17 17 17 17 17 17 17 17 17 17 17 ─────────────────────────────────────────────────────────── Mode 11 Palette Default Values ────────────────────────────────────────────────────────── Register 0 1 2 3 4 5 6 7 8 9 A B C D E F Value 0 37 37 37 37 37 37 37 37 37 37 37 37 37 37 37 ─────────────────────────────────────────────────────────── Mode D,E,10 and 12 Palette Default Values ────────────────────────────────────────────────────────── Register 0 1 2 3 4 5 6 7 8 9 A B C D E F Value 0 1 2 3 4 5 14 7 38 39 3A 3B 3C 3D 3E 3F ─────────────────────────────────────────────────────────── Mode 13 Palette Default Values ────────────────────────────────────────────────────────── Register 0 1 2 3 4 5 6 7 8 9 A B C D E F Value 0 1 2 3 4 5 6 7 8 9 A B C D E F ─────────────────────────────────────────────────────────── . COLOR REGISTERS The VGA is equipped with 256 Color Registers. A pixel or character in display memory consists of from one to eight bits of data. This data is used to address the 16 palette registers. The output of these palette registers is used in conjunction with the data in display memory to address the color registers. The color registers contain the color codes that are output to the digital-to-analog converters (DAC). The output of the DAC are sent to the monitor. Each of the color registers consists of a red,green,and blue component. Each of these color components is six bits wide. . COLOR REGISTERS ADDRESSING . COLOR REGISTER ORGANIZATION 1. Four banks of 64 color registers 2. Sixteen banks of 16 color registers . ACCESSING THE COLOR REGISTERS 1. Modifying color registers through BIOS 2. Modifying color registers directly Relative registers: ──────────────────────────────────────────────────── Address Read/Write Function 3C7 Write only PEL address during read 3C7 Read only DAC state 3C8 Read/Write PEL address during write 3C9 Read/Write PEL data register 3C6 Read/Write PEL mask ──────────────────────────────────────────────────── . COLOR CONVERSION 1. Gray Scale Gray shades are composed of equal amounts of red, green, and blue. White is the maximum gray scale value, and black is the minimum value. The VGA allocates six bits per color which provides 64 possible gray scales. These 64 levels of gray scale are achived using the six-bit color fields within the color registers. Gray scale using the color registers ──────────────────────────────────────────────────── Color Register Value Gray Scale ──────────────────────── Red Green Blue 0 0 0 0% saturation 1 1 1 1.6% saturation 2 2 2 3.2% saturation . . . . . . . . . . . . 63 63 63 100% saturation 2. Summing Colors to Gray Scale GRAY SCALE = (0.30 X RED) + (0.59 X GREEN) + (0.11 X BLUE) 3. Relative BIOS Calls ──────────────────────────────────────────────────────────────────── AH Subfunction (Hex) Function 10 AL = 1B Sum color values immediately to gray scale 12 BL = 33 Enable/Disable summing to gray scale at mode set ************************************ * * ******* VGA BIOS CALLS ****** * * ************************************ CONTROL ─────────────────────────────────────────────────────────── Mode Set Select Active Display Page Select Alternate Print Screen Routine Video Enable/Disable Display Switch Video Screen On/Off RETURN STATE ─────────────────────────────────────────────────────────── Return Curren Video State Return Video Information Read/Write Display Combination Code Return Functionality/State Information Save/Restore Video State INTERACTIVE ─────────────────────────────────────────────────────────── Set Cursor Type Set Cursor Position Read Cursor Position Cursor Emulation TEXT ─────────────────────────────────────────────────────────── Scroll Active Page Up Scroll Active Page Down Read Character/Attribute Write Character/Attribute Write Character Only Write Teletypewriter to Active Page Select Scan Lines for Text Modes Write String GRAPHICS ─────────────────────────────────────────────────────────── Write Dot Read Dot PALETTE ─────────────────────────────────────────────────────────── Set Color Palette Set Individual Palette Register Set Overscan (Boarder) Register Set All Palette Registers and Overscan Toggle Intensity/Blinking Bit Read Individual Palette Register Read Overscan Resister Read all Palette Registers and Overscan Default Palette Loading During Mode Set COLOR REGISTERS ─────────────────────────────────────────────────────────── Set Individual Color Register Set block of Color Registers Select Color Page Read Individual Color Register Read Block of Color Registers Read Current Color Page Number Sum Color Values to Gray Scale Default Palette Loading During Mode Set Summing to Gray Scales CHARACTER GENERATOR ─────────────────────────────────────────────────────────── User text Load with Reset ROM Monochrome Set with Reset ROM 8x8 Character Set Load with Reset Set Block Specifier ROM 8x16 Character Set Load with Reset User Alpha Load ROM Monochrome Set ROM 8x8 Character Set Load ROM 8x16 Character Set Load User Graphics Characters INT 1FH (8x8) User Graphics Characters Graphics Mode ROM 8x14 Character Set Load Graphics Mode ROM 8x8 Character Set Load Graphics Mode ROM 8x16 Character Set Load Return Character Generator Information ****************************************** * * *** VGA POST (DIAGNOSTIC) SEQUENCE *** * * ****************************************** ┌─────────────────────┐ │ Disable │ │ VGA 1* │ └─────────┬───────────┘ ┌────────────────┐ │ │ │ │ │ │ ┌─────────┴───────────┐ │ ┌─────────┴───────────┐ │ Check Other │ │ │ Dual Monitor │ │ Display Card Exit? │ │ │ Test 7* │ │ 2* │ │ └─────────┬───────────┘ └─────────┬───────────┘ │ │ │ │ │ │ │ ┌─────────┴───────────┐ ┌─────────┴───────────┐ │ │ Set Mode │ │ Enable │ │ │ 8* │ │ VGA 3* │ │ └─────────┬───────────┘ └─────────┬───────────┘ │ │ │ │ │ │ │ ┌─────────┴───────────┐ ┌─────────┴───────────┐ │ │ Test Vertical │ │ Set Corresponding │ │ │ Retrace Signal 9* │ │ Video Interrupt │ │ └─────────┬───────────┘ │ Vectors 4* │ │ │ └─────────┬───────────┘ │ │ │ │ ┌─────────┴───────────┐ │ │ │ Show ACER │ ┌─────────┴───────────┐ │ │ Copyright │ │ Test Video │ │ └─────────────────────┘ │ Buffer 5* │ │ └─────────┬───────────┘ │ │ │ │ │ ┌─────────┴───────────┐ │ │ Sense Monitor │ │ │ Type 6* │ │ └─────────┬───────────┘ │ │ │ │ │ └─────────────────┘ Note 1: Wake up VGA chip by programming port 46E8 hex bit 4 to 1. Program port 102 hex bit 0 to 1. Program port 46E8 hex bit 3 to 0 (disable the accessing of VGA memory and I/O) for the sake of testing other display cards' presence. Note 2: By writing 4 words to VRAM (B000h & B800h) read back If VRAM R/W O.K then set the correct equip_flag (40:10) value. Note 3: Program port 46E8 hex bit 3 to 1 (enable the accessing of VGA memory and I/O). Note 4: INT 10h : service routine entry INT 1Fh : 2nd 128 8x8 ascii code INT 43h : 1st 128 8x8 ascii code INT 1Dh : point to the CGA compatible table INT 6dh : keep the same value as INT 10h vector INT 42h : IBM (CGA,MDA,MGA) original INT 10 vector (F000:F065) Note 5: By writing pattern to VRAM then read back. If error occurs, sound 1 long 2 short error beep. Note 6: R G B -- 12h,12h,12h If port 3C2h bit 4 on, color monitor R G B -- 4,12h,4 If port 3C2h bit 4 on, mono monitor else, no monitor attached. Note 7: Set corresponding values to BIOS data area. Note 8: Set CRT mode according to the current flags setting. Note 9: Read input status register (3DA/3BA), if error occures, sound 1 long 3 short error beep.