User's Manual

Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0

9.1.1. ST00



Input 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

/ Sen

Reserved (0000)

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.