adv7195 Analog Devices, Inc., adv7195 Datasheet - Page 21

• Manufacturer Part Number: adv7195
• Description: Encoder With Three 11-bit Dacs And 10-bit Data Input
• Manufacturer: Analog Devices, Inc.

FILTER GAIN
FG (FG7–FG0)
(Address (SR4–SR0) = 10H)
Figure 34 shows the various operations under the control of the
Filter Gain register.
FG BIT DESCRIPTION
Filter Gain A (FG3–FG0)
These bits are used to program the gain A value, which varies
from response –8 to response +7 and are applied to Filter A.
Filter Gain B (FG4–FG7)
These bits are used to program the gain B value, which varies
from response –8 to response +7, and are applied to Filter B.
Refer to Sharpness Filter Control and Adaptive Filter Control
section for more detail.
GAMMA CORRECTION REGISTERS 0–13
(GAMMA CORRECTION 0–13)
(Address (SR5–SR0) = 14H–21H)
The Gamma Correction Registers are 14 8-bit-wide registers.
They are used to program the gamma correction Curves A and B.
Generally, gamma correction is applied to compensate for the
nonlinear relationship between signal input and brightness
level output (as perceived on the CRT). It can also be applied
wherever nonlinear processing is used.
Gamma correction uses the function:
where γ = gamma power factor.
Gamma correction is performed on the luma data only.
The user has the choice of two different curves, Curve A or
Curve B. At any one time only one of these curves can be used.
FG7
FG6
FILTER GAIN B
0 0 0 0
0 0 0 1
0 0 1 0
0 0 1 1
0 1 0 0
0 1 0 1
0 1 1 0
0 1 1 1
1 0 0 0
1 0 0 1
1 0 1 0
1 0 1 1
1 1 0 0
1 1 0 1
1 1 1 0
1 1 1 1
FG7–FG4
Signal
FG5
–8
–7
–6
–5
–4
–3
–2
–1
0
1
2
3
4
5
6
7
OUT
FG4
= (Signal
FG3
FILTER GAIN A
0 0 0 0
0 0 0 1
0 0 1 0
0 0 1 1
0 1 0 0
0 1 0 1
0 1 1 0
0 1 1 1
1 0 0 0
1 0 0 1
1 0 1 0
1 0 1 1
1 1 0 0
1 1 0 1
1 1 1 0
1 1 1 1
FG2
FG3–FG0
IN
)
γ
–8
–7
–6
–5
–4
–3
–2
–1
FG1
0
1
2
3
4
5
6
7
FG0
The response of the curve is programmed at seven predefined
locations. In changing the values at these locations the gamma
curve can be modified. Between these points linear interpola-
tion is used to generate intermediate values. Considering the
curve to have a total length of 256 points, the seven locations
are at: 32, 64, 96, 128, 160, 192, 224.
Locations 0, 16, 240, and 255 are fixed and cannot be changed.
For the length of 16 to 240 the gamma correction curve has to
be calculated as below:
where
y = gamma corrected output.
x = linear input signal.
γ = gamma power factor.
To program the gamma correction registers, the seven values
for y have to be calculated using the following formula:
where
x
n
y
Example:
y
y
y
y
The above will result in a gamma curve shown on the next
page, assuming a ramp signal as an input.
Rounded to the nearest integer.
(n–16)
n
32
64
96
128
= [(16/224)
= [(48/224)
= [(80/224)
= [(112/224)
= Value for x along x-axis at points:
= 32, 64, 96, 128, 160, 192, or 224.
= Value for y along the y-axis, which has to be written
300
250
200
150
100
50
0
0
into the gamma correction register.
y
GAMMA CORRECTION BLOCK OUTPUT
TO A RAMP INPUT
n
= [x
0.5
0.5
0.5
(n–16)
50
0.5
× 2 24] + 16 = 76
× 224] + 16 =120
× 224] + 16 = 150
× 224] + 16 = 174
/(240 – 16)]
SIGNAL INPUT
100
y = x
0.5
LOCATION
SIGNAL OUTPUT
γ
γ
150
× (240–16) + 16
200
ADV7195
250