ADV7181 AD [Analog Devices], ADV7181 Datasheet - Page 30

• Manufacturer Part Number: ADV7181
• Description: Multiformat SDTV Video Decoder
• Manufacturer: AD [Analog Devices]

ADV7181B
Table 31. AGC Modes
Input Video Type
Any
CVBS
Y/C
YPrPb
Luma Gain
LAGC[2:0] Luma Automatic Gain Control, Address 0x30 [7:0]
The luma automatic gain control mode bits select the mode of
operation for the gain control in the luma path.
There are ADI internal parameters to customize the peak white
gain control. Contact ADI for more information.
Table 32. LAGC Function
LAGC[2:0]
000
001
010(default)
011
100
101
110
111
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 only has an effect 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
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
customized by the use of internal parameters. Contact ADI for
more information.
Description
Manual fixed gain (use LMG[11:0]).
AGC (blank level to sync tip). No override through
peak white.
AGC (blank level to sync tip). Automatic override
through peak white.
Reserved.
Reserved.
Reserved.
Reserved.
Freeze gain.
Luma Gain
Manual gain luma.
Dependent on horizontal sync depth.
Peak White.
Dependent on horizontal sync depth.
Peak White.
Dependent on horizontal sync depth.
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Table 33. 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.
If read back, this register returns the current gain value.
Depending on the setting in the LAGC[2:0] bits, this is one of
the following values:
•
•
Table 34. LG/LMG Function
LG[11:0]/LMG[11:0]
LMG[11:0] = X
LG[11:0]
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)
Luma
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.
Chroma Gain
Manual gain chroma.
Taken from luma path.
_
Gain
=
(
0
<
Read/Write
Write
Read
Slow (TC = 2 sec)
Medium (TC = 1 sec)
Fast (TC = 0.2 sec)
Adaptive
Description
LG
2048
≤
4095
)
=
Description
Manual gain for luma
path.
Actually used gain.
0
...
2
(1)