Analog Devices ADV7850 Hardware Manual page 83

Function
sdp_man_gain_vcr
1
0 
sdp_y_gain_man[12:0], Addr 90 (SDP), Address 0x03[4:0]; Address 0x04[7:0]
This control is used to adjust the manual luma gain value. It is used if sdp_y_agc_en is set to 0. It also applies to the G channel in
component modes. The control has a range of 0.5 to 4.
Function
sdp_y_gain_man[12:0]
0x0558
The luma gain range is from 0.5 to 4.0.
Example:
To program the ADV7850 into manual fixed gain mode with a desired gain of 0.95:
• Use Equation 1 to convert the gain:
0.95 * 1024 = 972.8
• Truncate to integer value:
972.8 972
•
Convert to hexadecimal:
972  0x3CC
• Split into two registers and program:
sdp_y_gain_man[12:8] = 0x3
sdp_y_gain_man[7:0] = 0xCC
• Enable manual fixed gain mode:
Set sdp_y_agc_en to 0
sdp_y_gain_man_rb[12:0], Addr 90 (SDP), Address 0x54[4:0]; Address 0x55[7:0] (Read Only)
This readback provides the current luma gain.
Function
sdp_y_gain_man_rb[12:
0]
0x54[4:0]
0x55[7:0]
sdp_limit_y_gain, Addr 90 (SDP), Address 0x89[7]
This control is used to limit the luma gain.
Function
sdp_limit_y_gain
1
0 
Rev. A May 2012
Description
Manual gain used for VCR inputs value is sdp_y_gain_man
Automatic gain used for VCR inputs (valid only if sdp_y_agc_en set to 1)
Description
Default
<
512 SDP
Luma_Gain
=
Equation 1: SDP Luma Gain Formula
Description
sdp_y_gain_man_rb[12:8]
sdp_y_gain_man_rb[7:0]
Description
Limit luma gain to range of 50% to 200%
Normal operation
_ Y _ GAIN _ MAN [ 12 : ] 0
1024
83
≤
4095
= 0.5...4.0
ADV7850