Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0

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Figure 25 Display Fields and Dimensions CRxx Control Registers

 

 

 

 

 

 

CR00 Horizontal Total

 

 

 

 

 

 

 

 

CR03 Horizontal Blank End

 

 

 

 

 

 

 

CR05 Horizontal Sync End

 

 

 

 

 

 

 

CR04 Horizontal Sync Start

 

 

 

 

 

 

 

 

CR02 Horizontal Blank Start

 

 

 

 

 

 

 

 

CR01 Horizontal Display Enable End

 

 

CR06 Vertical Total

 

 

CR10 Vertical Sync Start

CR15 Vertical Blank Start

CR12 Vertical Display Enable End

Display

Horizontal Right Border

Horizontal Sync

CR16 Vertical Blank End

CR11 Vertical Sync End

Vertical Bottom Border

Blank (Vertical Front Porch

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Vertical Sync

 

 

 

 

 

 

 

 

Blank (Vertical Back Porch)

 

 

 

 

 

 

 

 

Vertical Top Border

 

 

 

 

 

 

 

 

 

 

crt_reg.vsd

9.6.1.CRXCRT Controller Index Register

I/O (and Memory Offset) Address:

3B4h/3D4h

Default:

0Uh (U=Undefined)

Attributes:

Read/Write

The value which can be supported at CRX is likely to be impacted by the X09 register which modifies the meaning of the extended CRxx registers.

Bit

Description

 

 

7:0

CRT Controller Register Index. These 8 bits are used to select any one of the CRT controller registers

 

to be accessed via the data port at I/O location 3B5h or 3D5h, depending upon whether the graphics

 

system is configured for MDA or CGA emulation. The data port memory address offsets are 3B5h/3D5h.

 

 

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Intel 815 manual CRXCRT Controller Index Register, Display Fields and Dimensions CRxx Control Registers