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PDF ACVP2205 Data sheet ( Hoja de datos )
| Número de pieza | ACVP2205 | |
| Descripción | Adaptive Combfilter Video Processor | |
| Fabricantes | ITT Semiconductors | |
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ACVP 2205
Adaptive Combfilter
Video Processor
Edition August 25, 1992
6251-336-2E
ITT Semiconductors
1 page  
ACVP 2205
Table 2–1: Variable luminance delay (Address 15)
Bits of low Byte
Number of
7 6 5 4 clock cycles
0 1 1 1 +4
0 1 1 0 +3
0 1 0 1 +2
0 1 0 0 +1
1××× 0
0 0 1 1 –1
0 0 1 0 –2
0 0 0 1 –3
0 0 0 0 –4
The luminance amplitude is adjustable by the contrast
multiplier. The multiplication factor is programmable be-
tween times 0 and times 2 in 64 steps via IM bus. If the
output signal of the multiplier is greater then 8 bit ( e.g.
caused by peaking) it is limited to the maximum value of
255. The contrast setting can be adapted automatically
to the room lighting by a photo sensor connected to pin
17 of the ACVP 2205. The signal of the photo sensor is
digitized in the ACVP 2205 and transferred in multiplex
operation to the CCU during vertical flyback. The CCU
calculates the new contrast and changes the contrast
multiplier value via IM bus.
A fixed value of 31 is added to the output of the contrast
multiplier causing a constant DC offset of the signal.
Thus the system transmits the negative undershoots
caused by peaking, to the D/A converter (see Fig. 2–3).
From the contrast multiplier, the digital luminance signal
is fed back to the VCU 2136. The 8 bit output signal con-
tains the information of 10 bits by a four–step (2 bits) pul-
sewidth modulation of the LSB. This noise shaping re-
duces truncation errors caused by cutted bits of the
contrast multiplier. Inside the VCU 2136 or VDU 2146,
the signal is connected to the luminance D/A converter.
The converter feeds the analog luminance signal to the
RGB matrix.
+255
+255
00
+31 Steps
–256
a) b) c)
Fig. 2–3: Adding 31 steps DC signal
a) peaked signal after filter
b) the same signal with added 31 steps, this means a
constant DC level or brightness
c) the signal at the output of the
luminance D/A converter
2.4. Black–Level–Expander
In many reproduced TV scenes, the contrast is not opti-
mum, and modifications of the contrast setting of the re-
ceiver may not produce an improvement. In this case a
black–level–expander enhances the contrast of the pic-
ture. Therefore the luminance signal is modified with an
adjustable, nonlinear function.
Criterion for the expansion is the dynamic range of the
video signal. In every field, the minimum and maximum
amplitudes Ymin and Ymax of the video signal are mea-
sured and stored. Based on these two values and the
adjustable coefficient K1, a tilt point Yt
Yt = K1 (Ymax – Ymin ) + Ymin
is established, above which there is no expansion, while
all luminance values below will be expanded (see Fig.
2–5).
Composite Video
Clamping
Circuit
Peaking
Contrast
Multiplier
Y D/A
Converter
White Balance,
Brightness
CRT Spot–Cutoff
S–VHS
Chroma
Mux.
A/D
Converter
Comb
Filter
Clock
Generator
MCU 2600
Lowpass
Filter
Phase
Comparator
IM Bus
Interface
RGB
IM Matrix
Bus
Horizontal
Flyback
Chroma
Bandpass
ACC,
Color
Killer
Decoder,
PAL Comp.
Color
Saturation
Multiplier
R–Y D/A
Converter
B–Y D/A
Converter
Beam
Current
Limiter
Fig. 2–4: Block diagram of the overall signal flow
R
G
B
5
5 Page 
ACVP 2205
Table 2–7: IM bus bits for general video processing
Parameter
Address
Label
Bit No.
(LSB = 0)
Default
Setting
14
SEC
15
0
14
NTSC
14
0
14
OUT
11
0
140
CFO
9
0
Typical
Operation
Value
0
0
1
0
Function
SECAM mode
0 = SECAM off
1 = SECAM on, chroma outputs high–impedance
NTSC or PAL mode
0 = PAL mode
1 = NTSC mode
Luminance and Chrominance output
0 = high–impedance
1 = outputs active
Disable adaptive combfilter
0 = adaptive combfilter enabled
1 = horizontal filtering (notch/bandpass) enabled
Table 2–8: IM bus bits for luminance processing
Parameter
Address
Label
Bit No.
(LSB = 0)
Default
Setting
11
PK
8–15
8
11
BAA
0–6
0
11
YBW
7
0
15
YBW2
0
0
12
CMIX
0
0
13
APWM
0
0
15
CT
10–15
32
15
SCT
8
0
15 LD 4–7 4
15
S–VHS
2
0
16 BR 0–7 –
20 DLP 0
0
27
RGBC
2–7
–
Typical
Operation
Value
16
1
1
0
0
0
40
1
0
0
127
1
32
Function
Horizontal peaking
00000000 = peaking curve 0
00000001 = peaking curve 1
00000010 = peaking curve 2
00000100 = peaking curve 3
00001000 = peaking curve 4
00010000 = peaking curve 5
00100000 = peaking curve 6
01000000 = peaking curve 7
10000000 = peaking curve 8
Adjustable coring for horizontal peaking
Luminance bandwidth (see section 4.)
Luminance bandwidth 2 (see section 4.)
Combfilter mix
0 = flat frequency response
1 = –6 dB reduction at fsc (see section 4.)
Additional pulsewidth modulation of the luminance
LSB
0 = disabled
1 = enabled
Set of the luminance contrast in 64 steps
Second chrominance trap
0 = on in SECAM
1 = off in SECAM
0 = off in PAL/NTSC
1 = on in PAL/NTSC
Variable luminance delay time (see Table 2–1)
S–VHS switch for chroma data DDS2 or DDS 1
0 = DDS2 normal operation
1 = DDS1 S–VHS operation
Brightness
Disable broadband LPF for S–VHS and combfilter
0 = LPF enabled
1 = LPF disabled
External RGB contrast
11
11 Page | ||
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| PDF Descargar | [ Datasheet ACVP2205.PDF ] | |
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