
ADV7183B
Table 33. AGC Modes
Input Video Type
Any
CVBS
Rev. B | Page 31 of 100
Luma Gain
Manual gain luma
Dependent on horizontal sync depth
Chroma Gain
Manual gain chroma
Dependent on color burst amplitude
Taken from luma path
Dependent on color burst amplitude
Taken from luma path
Dependent on color burst amplitude
Taken from luma path
Dependent on color burst amplitude
Taken from luma path
Taken from luma path
Peak white
Dependent on horizontal sync depth
Y/C
Peak white
YPrPb
Dependent on horizontal sync depth
Luma Gain
LAGC[2:0] Luma Automatic Gain Control,
Address 0x2C[7:0]
The luma automatic gain control mode bits select the mode of
operation for the gain control in the luma path.
ADI internal parameters are available to customize the peak
white gain control. Contact ADI sales for more information.
Table 34. LAGC Function
LAGC[2:0]
Description
000
Manual fixed gain (use LMG[11:0])
001
AGC (blank level to sync tip); peak white
algorithm off
010 (default)
AGC (blank level to sync tip); peak white
algorithm on
011
Reserved
100
Reserved
101
Reserved
110
Reserved
111
Freeze gain
LAGT[1:0] Luma Automatic Gain Timing,
Address 0x2F[7:6]
The luma automatic gain timing register allows the user to
influence the tracking speed of the luminance automatic gain
control. Note that this register has an effect only if the
LAGC[2:0] register is set to 001, 010, 011, or 100 (automatic
gain control modes).
If peak white AGC is enabled and active (see the
191H
STATUS_1[7:0] Address 0x10[7:0] section), the actual gain
update speed is dictated by the peak white AGC loop and, as a
result, the LAGT settings have no effect. As soon as the part
leaves peak white AGC, LAGT becomes relevant again.
The update speed for the peak white algorithm can be custom-
ized by the use of internal parameters. Contact ADI sales for
more information.
Table 35. LAGT Function
LAGT[1:0]
00
01
10
11 (default)
LG[11:0] Luma Gain, Address 0x2F[3:0];
Address 0x30[7:0]; LMG[11:0] Luma Manual Gain,
Address 0x2F[3:0]; Address 0x30[7:0]
Luma gain[11:0] is a dual-function register. If written to, a
desired manual luma gain can be programmed. This gain
becomes active if the LAGC[2:0] mode is switched to manual
fixed gain. Equation 1 shows how to calculate a desired gain.
Description
Slow (TC = 2 sec)
Medium (TC = 1 sec)
Fast (TC = 0.2 sec)
Adaptive
If read back, this register returns the current gain
value.
Depending on the setting in the LAGC[2:0] bits, one of these
gain values is returned
Luma manual gain value (LAGC[2:0] set to luma manual
gain mode)
Luma automatic gain value (LAGC[2:0] set to any of the
automatic modes)
Table 36. LG/LMG Function
LG[11:0]/LMG[11:0]
Read/Write
LMG[11:0] = X
Write
Description
Manual gain for luma
path
Actually used gain
LG[11:0]
Read
(
)
2
...
0
2048
4095
0
_
=
≤
<
=
LG
Gain
Luma
(1)