Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0

R

9.1.1.ST00Input Status 0

I/O (and Memory Offset) Address:

 

3C2h

 

 

 

 

Default:

 

 

 

 

00h

 

 

 

 

Attributes:

 

 

Read Only

 

 

7

6

 

5

4

3

0

 

 

 

CRT Int

 

Reserved (00)

 

RGB Cmp

 

 

Reserved (0000)

 

 

 

 

 

 

 

 

/ Sen

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Bit

 

 

 

 

 

Descriptions

 

 

 

 

 

 

 

7

CRT Interrupt Pending. Note that the generation of interrupts can be enabled, through bits [4,5] of the

 

 

 

 

Vertical Retrace End Register (CR11). This ability to generate interrupts at the start of the vertical

 

 

 

 

retrace interval is a feature that is typically unused by current software. This bit is here for EGA

 

 

 

 

compatibility.

 

 

 

 

 

 

 

 

 

0 = CRT (vertical retrace interval) interrupt is not pending.

 

 

 

 

 

1 = CRT (vertical retrace interval) interrupt is pending

 

 

 

 

 

 

 

 

 

 

 

 

6:5

Reserved. Read as 0s.

 

 

 

 

 

 

 

 

 

 

 

4

RGB Comparator / Sense. This bit returns the state of the output of the RGB output comparator(s).

 

 

 

 

BIOS uses this bit to determine whether the display is a color or monochrome CRT.

 

 

 

 

0 = Monochrome

 

 

 

 

 

 

 

 

 

1 = Color

 

 

 

 

 

 

 

 

 

 

BIOS blanks the screen or clears the frame buffer to display only black. Next, BIOS configures the

 

 

 

 

D-to-A converters and the comparators to test for the presence of a color display. Finally, if the BIOS

 

 

 

 

does not detect any colors, it tests for the presence of a display. The result of each such test is read via

 

 

 

 

this bit.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3:0

Reserved. Read as 0s.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

80

Page 80
Image 80
Intel 815 manual 1. ST00Input Status, Bit