VGA/SVGA Video Programming--VGA Functional Index

Home Register Memory Sequencing Cursor Attribute DAC Display Misc Back

Hardware Level VGA and SVGA Video Programming Information Page VGA Functional Index

Register Access Functions
These fields control the acessability/inaccessability of the VGA registers. These registers are used for compatibiltiy with older programs that may attempt to program the VGA in a fashion suited only to an EGA, CGA, or monochrome card.

CRTC Registers Protect Enable -- Vertical Retrace End Register
Enable Vertical Retrace Access -- End Horizontal Blanking Register
Input/Output Address Select -- Miscellaneous Output Register

Display Memory Access Functions
These fields control the way the video RAM is mapped into the host CPU's address space and how memory reads/writes affect the display memory.

Bit Mask -- Bit Mask Register
Chain 4 Enable -- Sequencer Memory Mode Register
Chain Odd/Even Enable -- Miscellaneous Graphics Register
Color Compare -- Color Compare Register
Color Don't Care -- Color Don't Care Register
Enable Set/Reset -- Enable Set/Reset Register
Extended Memory -- Sequencer Memory Mode Register
Host Odd/Even Memory Read Addressing Enable -- Graphics Mode Register
Host Odd/Even Memory Write Addressing Enable -- Sequencer Memory Mode Register
Logical Operation -- Data Rotate Register
Memory Map Select -- Miscellaneous Graphics Register
Memory Plane Write Enable -- Map Mask Register
Odd/Even Page Select -- Miscellaneous Output Register
RAM Enable -- Miscellaneous Output Register
Read Map Select -- Read Map Select Register
Read Mode - Graphics Mode Register
Rotate Count -- Data Rotate Register
Set/Reset -- Set/Reset Register
Write Mode -- Graphics Mode Register

Display Sequencing Functions
These fields affect the way the video memory is serialized for display.

256-Color Shift Mode -- Graphics Mode Register
9/8 Dot Mode -- Clocking Mode Register
Address Wrap Select -- CRTC Mode Control Register
Alphanumeric Mode Disable -- Miscellaneous Graphics Register
Asynchronous Reset -- Reset Register
Byte Panning -- Preset Row Scan Register
Character Set A Select -- Character Map Select Register
Character Set B Select -- Character Map Select Register
Divide Memory Address Clock by 4 -- Underline Location Register
Double-Word Addressing -- Underline Location Register
Pixel Shift Count -- Horizontal Pixel Panning Register
Line Compare -- bit 9: Maximum Scan Line Register, bit 8: Overflow Register, bits 7-0: Line Compare Register
Line Graphics Enable -- Attribute Mode Control Register
Map Display Address 13 -- CRTC Mode Control Register
Map Display Address 14 -- CRTC Mode Control Register
Maximum Scan Line -- Maximum Scan Line Register
Offset -- Offset Register
Pixel Panning Mode -- Attribute Mode Control Register
Preset Row Scan -- Preset Row Scan Register
Scan Doubling -- Maximum Scan Line Register
Screen Disable -- Clocking Mode Register
Shift Four Enable -- Clocking Mode Register
Shift/Load Rate -- Clocking Mode Register
Shift Register Interleave Mode -- Graphics Mode Register
Start Address -- bits 15-8: Start Address High Register, bits 7-0: Start Address Low Register
Sycnchronous Reset -- Reset Register
Word/Byte Mode Select -- CRTC Mode Control Register

Cursor Functions
These fields affect the operation of the cursor displayed while the VGA hardware is in text mode.

Cursor Disable -- Cursor Start Reguster
Cursor Location -- bits 15-8: Cursor Location High Register, bits 7-0: Cursor Location Low Register
Cursor Scan Line End -- Cursor End Register
Cursor Scan Line Start -- Cursor Start Reguster
Cursor Skew -- Cursor End Register

Attribute Functions
These fields control the way the video data is submitted to the RAMDAC, providing color/blinking capability in text mode and facilitating the mapping of colors in graphics mode.

8-bit Color Enable -- Attribute Mode Control Register
Attribute Address -- Attribute Address Register
Attribute Controller Graphics Enable -- Attribute Mode Control Register
Blink Enable -- Attribute Mode Control Register
Color Plane Enable -- Color Plane Enable Register
Color Select 5-4 -- Color Select Register
Color Select 7-6 -- Color Select Register
Internal Palette Index -- Palette Registers
Monochrome Emulation -- Attribute Mode Control Register
Overscan Palette Index -- Overscan Color Register
Underline Location -- Underline Location Register
Palette Address Source -- Attribute Address Register
Palette Bits 5-4 Select -- Attribute Mode Control Register

DAC Functions
These fields allow control of the VGA's 256-color palette that is part of the RAMDAC.

DAC Write Address -- DAC Address Write Mode Register
DAC Read Address -- DAC Address Read Mode Register
DAC Data -- DAC Data Register
DAC State -- DAC State Register

Display Generation Functions
These fields control the formatting and timing of the VGA's video signal output.

Clock Select -- Miscellaneous Output Register
Display Disabled -- Input Status #1 Register
Display Enable Skew -- End Horizontal Blanking Register
Divide Scan Line Clock by 2 -- CRTC Mode Control Register
Dot Clock Rate -- Clocking Mode Register
End Horizontal Display -- End Horizontal Display Register
End Horizontal Blanking -- bit 5: End Horizontal Retrace Register, bits 4-0: End Horizontal Blanking Register,
End Horizontal Retrace -- End Horizontal Retrace Register
End Vertical Blanking -- End Vertical Blanking Register
Horizontal Retrace Skew -- End Horizontal Retrace Register
Horizontal Sync Polarity -- Miscellaneous Output Register
Horizontal Total -- Horizontal Total Register
Memory Refresh Bandwidth -- Vertical Retrace End Register
Start Horizontal Blanking -- Start Horizontal Blanking Register
Start Horizontal Retrace -- Start Horizontal Retrace Register
Start Vertical Blanking -- bit 9: Maximum Scan Line Register, bit 8: Overflow Register, bits 7-0: Start Vertical Blanking Register
Sync Enable -- CRTC Mode Control Register
Vertical Display End -- bits 9-8: Overflow Register, bits 7-0: Vertical Display End Register
Vertical Retrace End -- Vertical Retrace End Register
Vertical Retrace -- Input Status #1 Register
Vertical Retrace Start -- bits 9-8: Overflow Register, bits 7-0: Vertical Retrace Start Register
Vertical Sync Polarity -- Miscellaneous Output Register
Vertical Total -- bits 9-8: Overflow Register, bits 7-0: Vertical Total Register

Miscellaneous Functions
These fields are used to detect the state of possible VGA hardware such as configuration switches/jumpers and feature connector inputs.

Feature Control Bit 0 -- Feature Control Register
Feature Control Bit 1 -- Feature Control Register
Switch Sense -- Input Status #0 Register

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All pages are Copyright © 1997, 1998, J. D. Neal, except where noted. Permission for utilization and distribution is subject to the terms of the FreeVGA Project Copyright License.