A49
Appendix A Scaling and I/0 Timing
Register Calculations
The calculated values are used to program the registers controlling the total active
pixels and lines in the input frame and the output field, as well as the vertical
scaling register and the clock PLL registers. These calculations assume pixel
resolution for synchronizing the graphics controller, master interface operation
unless otherwise stated, and require the following input values:
MFP—Minimum Front Porch Blanking in the Input in Clocks = max
(12, Controller_Minimum_Front_Porch_Blanking_Clocks);
MBP—Minimum Back Porch Blanking in the Input in Clocks = max
(4, Controller_Minimum_Back_Porch_Blanking_Clocks);
VOC—desired Vertical Overscan Compensation (e.g., 0.15)
HOC—desired Horizontal Overscan Compensation (e.g., 0.15)
V_ACTIVEI—Active Lines per Input Frame (e.g., 480 or 600 or 768)
H_ACTIVE—Active Pixels per Input Line (e.g., 640 or 800 or 1024)
ALO—Target Active Lines per Output Field (See Table A-3)
TLO—Total Lines per Output Field (See Table A-3)
ATO—Active Time per Output Line (See Table A-3)
TTO—Total Time per Output Line (See Table A-3)
Tables A-1 and A-2 contain details of the supported video output formats.
Table A-3 details the constant software values depending on the video output.
Figures A-1 through A-8 illustrate allowable overscan compensation pairs for the
most common desktop active resolutions. Tables A-3 through A-27 list the most
common overscan values for the 640 x 480, 800 x 600, and 1024 x 768 active
resolutions that enable dual display on both the VGA monitor and TV.
100381B
Conexant
A-1
CONEXANT [ CONEXANT SYSTEMS, INC ]
