Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0

R

9.6.2.CR00Horizontal Total Register

I/O (and Memory Offset) Address:

3B5h/3D5h (index=00h)

Default:

00h

Attributes:

Read/Write (Group 0 Protection)

This register is used to specify the total length of each scan line. This encompasses both the part of the scan line that is within the active display area and the part that is outside of it. This register is extended to cover 16x12 resolution using CR35 and CR39.

Bit

Description

 

 

7:0

Horizontal Total. This field should be programmed with a value equal to the total number of character

 

clocks within the entire length of a scan line, minus 5.

 

 

9.6.3.CR01Horizontal Display Enable End Register

I/O (and Memory Offset) Address:

3B5h/3D5h (index=01h)

Default:

Undefined

Attributes:

Read/Write (Group 0 Protection)

This register is used to specify the end of the part of the scan line that is within the active display area relative to its beginning. In other words, this is the horizontal width of the active display area.

Bit

Description

 

 

7:0

Horizontal Display Enable End. This field should be programmed with a value equal to the number of

 

character clocks that occur within the part of a scan line that is within the active display area, minus 1.

 

 

9.6.4.CR02Horizontal Blanking Start Register

I/O (and Memory Offset) Address:

3B5h/3D5h (index=02h)

Default:

Undefined

Attributes:

Read/Write (Group 0 Protection)

This register is used to specify the beginning of the horizontal blanking period relative to the beginning of the active display area of a scan line.

Bit

Description

 

 

7:0

Horizontal Blanking Start. This field should be programmed with a value equal to the number of

 

character clocks that occur on a scan line from the beginning of the active display area to the beginning

 

of the horizontal blanking.

 

 

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Intel 815 manual 2. CR00Horizontal Total Register, 3. CR01Horizontal Display Enable End Register