Analog Devices ADV8005 Hardware Reference Manual page 100

UG-707
Similar to the autophase, the auto position block is designed to tune the ADC sampling clock frequency in a device with an analog front end. To
carry it out, the block will analyse the graphics input and return the top, bottom, left and right pixel vacancy numbers. This information, along
with the input standard format, can then be used to adjust the ADC sampling clock frequency.
Figure 51 shows the timing parameters for graphics inputs.
It returns the number of pixels from:
•
End of HSync to the start of active video
•
End of Active video to start of HSync
The autoposition also returns the number of lines from:
•
End of VSync to start of active video
•
End of active video to start of VSync
The readbacks are updated with every VSync period. It is required that the input to the autoposition and autophase blocks is in RGB format. If
the input is in YCrCb format, the
the input is RGB, then the CSC should be bypassed.
Before running the auto-position software routine, ensure a bright test pattern is used. For example a white RGB flat field which will have valid
video on the first and last pixel in each line. The bright color makes it easier for the algorithm to detect the blank area.
Figure 51: Graphics Video Timing Parameters
auto_phpo_byp_csc must be cleared, enabling the
ADV8005 Hardware Reference Manual
ADV8005
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to perform the color space conversion to RGB. If