if X1 ≧ X3 or Y1> Y3
Normal, high resolution 1 dot
Rotating / HDTV time 8 dots
The erase light is performed. In this case, erase write is performed assuming that the area is set to (X1, Y1), (X3 = X1 + 1, Y3 = Y1).
Erase light when normal and high resolution and VBE = 0 is out of the frame buffer during the display period. If the X3 coordinate is set beyond the display screen, erase light will continue for 4 pixels at normal time and 8 pixel at high resolution after the last valid data (falling edge of HTIM), and erase light will be performed outside the other display screens. not.
When the erase light range is set in the display screen, erase light outside the display range is not performed at all.
Erase lights are not affected by clipping.
In HDTV, frame buffer scaling, and rotation display, the frame buffer cannot be erased during display. In this case, the erase light is performed during the vertical blanking period (V_BLANK), so there is not enough time to erase the entire screen. If you want to erase the entire screen, you need to fill the unerased area with polygons at the start of drawing.
The number of pixels required for V blank erase is
(X3−X1 + 1) × (Y3−Y1 + 1) × 8
It is represented by If this is less than the number of pixels available for V blank erase, the erase light is complete.
The number of pixels that can be used for V blank erase is
{(Number of pixels in one raster) −200}
X x {(number of rasters in one field)-(number of displayed rasters)}
It becomes. The values are as follows: