Cp Offset Block; Figure 73: Channel A, B, And C Automatic Value Selection - Analog Devices Advantiv ADV7604 Hardware Manual

10.4 CP Offset Block

The offset block consists of three independent adders, one for each channel. Using the
B_OFFSET, and C_OFFSET
offset used can come from two different sources:
1. The ADV7604 includes an automatic selection of the offset value, dependent on the CSC
mode that is programmed by the user. The
derive offset values.
2. A manual, user defined value can be programmed.
When the offset registers (A_OFFSET, B_OFFSET, and C_OFFSET) contain the value 0x3FF (reset
default), the offset used is determined using the automatic selection process. For any other value in
the offset registers, the automatic selection is disabled and the user-programmed offset value is
applied directly to the video. Refer to the flowchart in

Figure 73: Channel A, B, and C Automatic Value Selection

In some applications, it is desirable to use the AGC to gain the signal to a smaller range, then use
the Offset block to preserve the synchronizations (by lifting the whole video signal up), and thus
output the full digitized waveform (including synchronizations) within the 10-bit output range. For
this application, the offset values are very important. Refer to the description of AGC_TAR_MAN.
For RGB type output data, the three offset values should be programmed to 0 or 64 (desired code
output for black video). For YPbPr type output data, A_OFFSET[9:0] should be set to 64 (desired
code for black); B_OFFSET[9:0] and C_OFFSET[9:0] (for Pr and Pb) are typically set to 512 (mid
range).
Notes:
• Adding an excessive offset onto the data will result in clipping of the signal.
• The offset value can only be positive; it is an unsigned number.
Rev. F August 2010
registers, a fixed offset value can be added to the data. The actual
RGB_OUT
241
and OP_656_RANGE
Figure 73.
ADV7604
A_ OFFSET,
bits are used to