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STV2050A - BLANKING OF VIDEO SIGNALS

8 BLANKING OF VIDEO SIGNALS

The output of the RGB signals can be set to 0V during the horizontal and vertical retrace. The

function is controlled by the D6 register. The horizontal and vertical retrace blanking function

can be enabled independently.

8.1 HORIZONTAL BLANKING

The HBE bit in the D6 register is used to enable/disable the horizontal blanking.

The start and end edge positions are determined by the HVB[5:0] bits in the D6 register.

If the horizontal blanking is enabled, the video outputs are set to 0V from the HVB clock cycles

before grid line number 15 until the HVB clock cycles after grid line number 1. The useful

range for the HVB is one horizontal grid distance. This function is similar to the border line

function.

If ‘0’ is programmed, grid lines no. 15 and no. 1 are not blanked.

Figure 24. Horizontal Grid Lines

Note: If the HVB values are greater than the HGD values, unexpected effects will appear on the screen.

8.2 VERTICAL BLANKING

The enable/disable control is the VBE bit in the D6 register.

The start and end edge positions are determined using the VVB[5:0] bits in the D6 register.

The video blanking function ends when the programmed number of VVB video lines, following

vertical grid line no. 0, are finished and the next video line following the end of the DAC retrace

mode (DCT) has begun.

The VVB range is one vertical grid distance. The function works the same as the border line

function. If ‘0’ is programmed, grid lines no. 0 and no. 12 are not blanked. If the values pro-

HBE

0: Horizontal Blanking Off

1: Horizontal Blanking On

VBE

0: Vertical Blanking Off

1: Vertical Blanking On

Horizontal Grid Lines

HVB

0V DAC Output

HVB

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