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+ VGA/SVGA Video Programming--Attribute Controller Registers
+
+
+
+Home Back
+
Hardware Level VGA and SVGA Video Programming Information
+Page
+
+Attribute Controller Registers
+
+
+
+ The Attribute Controller
+Registers are accessed via a pair of registers, the Attribute Address/Data
+Register and the Attribute Data Read Register. See the Accessing
+the VGA Registers section for more detals. The Address/Data Register
+is located at port 3C0h and the Data Read Register is located at port 3C1h.
+
+
+Attribute Address Register(3C0h)
+
+
+| 7 |
+
+6 |
+
+5 |
+
+4 |
+
+3 |
+
+2 |
+
+1 |
+
+0 |
+
+
+
+ |
+
+ |
+
+PAS |
+
+Attribute Address |
+
+
+
+PAS -- Palette Address Source
+"This bit is set to 0 to load color values to the registers in the
+internal palette. It is set to 1 for normal operation of the attribute
+controller. Note: Do not access the internal palette while this bit is
+set to 1. While this bit is 1, the Type 1 video subsystem disables accesses
+to the palette; however, the Type 2 does not, and the actual color value
+addressed cannot be ensured."
+-
+Attribute Address
+This field specifies the index value of the attribute register to be
+read or written.
+
+
+
+Palette Registers (Index 00-0Fh)
+
+
+| 7 |
+
+6 |
+
+5 |
+
+4 |
+
+3 |
+
+2 |
+
+1 |
+
+0 |
+
+
+
+ |
+
+ |
+
+Internal Palette Index |
+
+
+
+Internal Palette Index
+"These 6-bit registers allow a dynamic mapping between the text
+attribute or graphic color input value and the display color on the CRT
+screen. When set to 1, this bit selects the appropriate color. The Internal
+Palette registers should be modified only during the vertical retrace interval
+to avoid problems with the displayed image. These internal palette values
+are sent off-chip to the video DAC, where they serve as addresses into
+the DAC registers."
+
+
+Attribute Mode Control Register
+(Index 10h)
+
+
+| 7 |
+
+6 |
+
+5 |
+
+4 |
+
+3 |
+
+2 |
+
+1 |
+
+0 |
+
+
+
+| P54S |
+
+8BIT |
+
+PPM |
+
+ |
+
+BLINK |
+
+LGE |
+
+MONO |
+
+ATGE |
+
+
+
+P54S -- Palette Bits 5-4 Select
+"This bit selects the source for the P5 and P4 video bits that act
+as inputs to the video DAC. When this bit is set to 0, P5 and P4 are the
+outputs of the Internal Palette registers. When this bit is set to 1, P5
+and P4 are bits 1 and 0 of the Color Select register."
+
8BIT -- 8-bit Color Enable
+"When this bit is set to 1, the video data is sampled so that eight
+bits are available to select a color in the 256-color mode (0x13). This
+bit is set to 0 in all other modes."
+-
+PPM -- Pixel Panning Mode
+
+
This field allows the upper half of the screen to pan independently
+of the lower screen. If this field is set to 0 then nothing special occurs
+during a successful line compare (see the Line
+Compare field.) If this field is set to 1, then upon a successful line
+compare, the bottom portion of the screen is displayed as if the Pixel
+Shift Count and Byte Panning fields are
+set to 0.
+
BLINK - Blink Enable
+"When this bit is set to 0, the most-significant bit of the attribute
+selects the background intensity (allows 16 colors for background). When
+set to 1, this bit enables blinking."
+-
+LGA - Line Graphics Enable
+
+
This field is used in 9 bit wide character modes to provide continuity
+for the horizontal line characters in the range C0h-DFh. If this field
+is set to 0, then the 9th column of these characters is replicated from
+the 8th column of the character. Otherwise, if it is set to 1 then the
+9th column is set to the background like the rest of the characters.
+-
+MONO - Monochrome Emulation
+
+
This field is used to store your favorite bit. According to IBM, "When
+this bit is set to 1, monochrome emulation mode is selected. When this
+bit is set to 0, color |emulation mode is selected." It is present and
+programmable in all of the hardware but it apparently does nothing. The
+internal palette is used to provide monochrome emulation instead.
+-
+ATGE - Attribute Controller Graphics Enable
+"When set to 1, this bit selects the graphics mode of operation."
+
+
+
+Overscan Color Register (Index 11h)
+
+
+| 7 |
+
+6 |
+
+5 |
+
+4 |
+
+3 |
+
+2 |
+
+1 |
+
+0 |
+
+
+
+| Overscan Palette Index |
+
+
+
+Overscan Palette Index
+"These bits select the border color used in the 80-column alphanumeric
+modes and in the graphics modes other than modes 4, 5, and D. (Selects
+a color from one of the DAC registers.)"
+
+
+Color Plane Enable Register (Index
+12h)
+
+
+| 7 |
+
+6 |
+
+5 |
+
+4 |
+
+3 |
+
+2 |
+
+1 |
+
+0 |
+
+
+
+ |
+
+ |
+
+ |
+
+ |
+
+Color Plane Enable |
+
+
+
+
+-
+Color Plane Enable
+"Setting a bit to 1, enables the corresponding display-memory color
+plane."
+
+
+
+Horizontal Pixel Panning Register
+(Index 13h)
+
+
+| 7 |
+
+6 |
+
+5 |
+
+4 |
+
+3 |
+
+2 |
+
+1 |
+
+0 |
+
+
+
+ |
+
+ |
+
+ |
+
+ |
+
+Pixel Shift Count |
+
+
+
+Pixel Shift Count
+"These bits select the number of pels that the video data is shifted
+to the left. PEL panning is available in both alphanumeric and graphics
+modes."
+
+
+Color Select Register (Index 14h)
+
+
+| 7 |
+
+6 |
+
+5 |
+
+4 |
+
+3 |
+
+2 |
+
+1 |
+
+0 |
+
+
+
+ |
+
+ |
+
+ |
+
+ |
+
+Color Select 7-6 |
+
+Color Select 5-4 |
+
+
+
+Color Select 7-6
+"In modes other than mode 13 hex, these are the two most-significant
+bits of the 8-bit digital color value to the video DAC. In mode 13 hex,
+the 8-bit attribute is the digital color value to the video DAC. These
+bits are used to rapidly switch between sets of colors in the video DAC."
+
Color Select 5-4
+"These bits can be used in place of the P4 and P5 bits from the
+Internal Palette registers to form the 8-bit digital color value
+to the video DAC. Selecting these bits is done in the Attribute Mode Control
+register (index 0x10). These bits are used to rapidly switch between colors
+sets within the video DAC."
+Notice: All trademarks used or referred to on this page are the property
+of their respective owners.
+
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.
+
+