Cirrus-logic AN269 Manuel d'utilisateur télécharger pdf (Page 40)

40 AN269REV1

AN269

6.3.3 Vertical Alignment Signals

The vertical timing alignment signals are easily determined by looking at Figure 21.

The total number of lines is equal to the vertical resolution (notice there are no “blank” lines):

VLinesTotal = (vertical resolution) - 1

The VCSYNC signal becomes active when the vertical line counter is VLinesTotal - 1 and becomes inac-

tive when it is VLinesTotal - 2. Therefore:

VSyncStart = VLinesTotal - 1

VSyncStop = VLinesTotal - 2

Another result of having no “blank” lines is that the active region covers all of the horizontal lines, so the

active region is the entire vertical width:

VActiveStart = VLinesTotal

VActiveStop = VLinesTotal + 1

VCSYNC

HSYNC

Single Video Frame

SPCLK

First Line

Vertical Line

Counter Value

Count = VLinesTotal

Count = VLinesTotal - 1

Count = VLinesTotal - 2

Count =0

Count = VLinesTotal

Count = VLinesTotal - 1

Figure 21. Frame Type 2 Display Vertical Timing

1 2 ... 35 36 37 38 39 40 41 42 43 44 45 ... 64 65

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Cirrus-logic AN269 Manuel d'utilisateur Page 40