Cirrus Logic AN269 - Manual (Page 36)

36 AN269REV1
AN269
6.3.2 Horizontal Alignment Signals
To determine the length of time spent on a single horizontal line, the refresh rate is multiplied by the ver-
tical resolution, and inverted (1/X), yielding the value LinePeriod:
LinePeriod = 1 / [(refresh rate) * (vertical resolution)]
From that, the number of VIDCLK periods per line (NumVideoClocks) is:
NumVideoClocks = LinePeriod per VidClkPeriod
Note that the number of available video clocks can also be derived by adding up the number of clocks in
each region, but this approach will guarantee a more accurate line frequency.
The value of NumVideoClocks will be the total number of “available” clocks for all regions of time in the
horizontal line. In order to visualize this quantity, the see
Figure 20 . Note that the NumVideoClocks quan-
tity represents the total number of VIDCLKs per horizontal line, and therefore will be HClksTotal+1.